having engine trouble with my 5.7 Mercruiser Horizon MPI.

[newbienewb]

hi all,
Some time ago (actually at the end of the previous aussie summer), i posted a thread about issues i was having with poor holeshot.

I parked the boat for winter, and have been running it around over the last week, and not only am i still having problems, things seem to be getting worse. Im hoping someone can help.

Boat is a 7M australian whittley cruisemaster. around the 2 ton mark - maybe a little more.

Engine is a 5.7 Mercruiser Horizon. I think around 2002 vintage. Fuel is cool fuel I, i believe. Compression test showed up no serious issues. One cylinder is slightly down, but nothing serious.

1) When cold (ie within about the first twenty minutes of starting) then engine seems to be slightly more responsive on holeshot. After that it seems to be quite sluggish on takeoff.

2) Any time i holeshot (regardless of hot or cold), i get terrible pinging from the engine. I have emptied all fuel and have refilled it with premium unleaded (98 octane). It still pings.

3) At full throttle on holeshot, I'm barely able to achieve about 2900 RPM. To me this seems very very low. Seems to lack a lot of horsepower. When up on the plane, if i push it hard, i will get about 4100rpm on a really flat water.

4) Just today, it has started "surging" quite badly. we were cruising along about 28 knots, and it just lost a whole lot of power. I backed right off, and it seemed to idle along fine, so i powered back up again and it seemed to be lacking even more power. Once i finally got out of the hole, and cruising at about 28-30 knots, it now has a notable surge.

5) As i was loading it on the trailer, i powered up slightly to help get up to the bow stop, and it seems that even ar around 1200 rpm it has a notable surge now as well.

So, im trying to think of what it could be. Im happy to spend money to fix it, but if possible would rather not throw good money after bad.

Fuel Pump?, Distributor? Something else?

Would really appreciate any ideas anyone can throw my way. Thanks so much guys. Much appreciated.

Dave

[shaungonemad]

Check your timing and your fuel pressure they should be the easiest things to check.

[newbienewb]

Thanks Sean. I have a fuel pressure tester at home so will check that when I get home from work tonight.

Does anyone know what the fuel pressure test should be?. I have been told 30psi at 1800 rpm.

Also timing?. Happy to read any documentation if anyone can point me in the right direction.

Thanks kindly

Dave


Sent from my iPhone using Tapatalk

[juggernaut]

You may get more of a response over on the clubsearay forum since mercruisers of all guises powered some sort of Sea Ray at some time.

[mal555]

With the holeshot issue, what is the pitch and diameter of the prop? Is the leg fully retracted down?
Fit a Stingray hydrofoil to the cavitation plate, these boats perform better with both holeshot and lateral trim once up on the plane with this low cost addition.
As a first call, change your fuel filter.
If propped correctly, you should be able to pull 4800 rpm at least, it sounds like she is over-propped and labouring hard.

[newbienewb]

With the holeshot issue, what is the pitch and diameter of the prop? Is the leg fully retracted down?
Fit a Stingray hydrofoil to the cavitation plate, these boats perform better with both holeshot and lateral trim once up on the plane with this low cost addition.
As a first call, change your fuel filter.
If propped correctly, you should be able to pull 4800 rpm at least, it sounds like she is over-propped and labouring hard.

Hi Mal,

Yep, the leg is fully down when attempting to get out of the hole.
Ill have to have a look into the hydrofoil - not exactly sure what that is! :)
I changed the fuel filter at the end of last season so I think that should be OK.
The sterndrive leg is a bravo three (twin prop), with 20P props on it. The ratio on the leg is 2.00. Im not sure if this is appropriate or not. Ive been trying to find a website that can help advise of correct prop pitch for my boat configuration.

@juggernaut - Thanks for that!. Ill head over there and see if anyone can help out.

Thanks guys - appreciate the help and advice.

[mal555]

Hi Mal,

Yep, the leg is fully down when attempting to get out of the hole.
Ill have to have a look into the hydrofoil - not exactly sure what that is! :)
I changed the fuel filter at the end of last season so I think that should be OK.
The sterndrive leg is a bravo three (twin prop), with 20P props on it. The ratio on the leg is 2.00. Im not sure if this is appropriate or not. Ive been trying to find a website that can help advise of correct prop pitch for my boat configuration.

@juggernaut - Thanks for that!. Ill head over there and see if anyone can help out.

Thanks guys - appreciate the help and advice.
111465

The photo uploaded upside down for some reason, but there it is. There are a number of options, but these simple versions, Stingray Original, work great. This photo is not a Cruisemaster btw, just and example of the product.

just with the props, never just assume whoever fitted the props originally actually knew what they were doing as far as getting the combination correct ;)

[brett62]

I just checked under my cruisemaster deck and found well over a 100 litres of water sitting in the hull and that's what I could see. If you haven't had a look down the inspection ports I would.

[brett62]

Dave I will also be putting the boat over a weigh bridge in a few weeks and I will let you know what the real weight of these hulls are. I have heard so many different weights for them and will be well over 2 ton I am sure. Start adding people, fuel,water and all the other crap we carry you will be 3 ton. mal555 would agree I think.

As with prop size I am running a bravo one drive same 5.7l 300hp engine and have a four bladed prop 14 1/4 x 17. I don't have any trouble getting out on the plane. Like Mal said you need to make sure your engine is getting it's rev range and you don't want it to take a life time to get there either. A mate has a SL 7m with the bravo 3 leg, not sure what prop size he is running and he has no trouble at all. The bravo 3 drive works well on these boats.

[newbienewb]

Hi Guys,

Mal - I found the Mercruiser prop tor tool on their website and filled that out to the best of my knowledge. It recommends a pitch of 24. Currently I have 20. If im understanding pitch correctly, a pitch of 20 should get me out of the hole easier than 24.

Ill have to have a look into the hydrofoil.

Brett - thanks very much for that. I think your feedback just further affirms my suspicions that my eninge seems really quite sluggish. What sort of RPM are you pulling on takeoff?

It will be very interesting to hear what the boat weighs in at when you put it on the weight bridge. Ive often eyed off the one at the BP on eastlink (Melbourne), but never actually stopped to follow through.

Where are the inspection ports you are talking about?. The only thing like that I can see are the two holes on the corners of the engine cover. But they simply feed into where the bilge is anyway. I suspect im missing something.

Thanks guys. Look forward to hearing back

Dave

[mal555]

Don't hesitate to call someone like Neville Whittley or their technical department if you need advice also, he has always seemed very approachable, chatty and quite genuine at boat shows previously.
I haven't had any experience with the Bravo III, so can't comment.

A "fully loaded" Cruisemaster will go to 3.5 tonnes on the trailer, maxed out with everything for a few days away, inflatable dinghy, small outboard etc., remember these boats have everything....including the kitchen sink :)

[brett62]

Dave inspection ports are a about in line with the back table mount. They give you access to your fresh water plumbing. Just need to roll the carpet back.

I hit the throttle to 4000rpm and that lifts me on to the plan in no time. I then back it off. I can get on the plan with out having to bring the leg all the way down also. I don't use the tabs at all until I am up and running and then I need to throw a little in due to the single screw throwing a chine down and this will change with speed.


Hi Guys,

Mal - I found the Mercruiser prop tor tool on their website and filled that out to the best of my knowledge. It recommends a pitch of 24. Currently I have 20. If im understanding pitch correctly, a pitch of 20 should get me out of the hole easier than 24.

Ill have to have a look into the hydrofoil.

Brett - thanks very much for that. I think your feedback just further affirms my suspicions that my eninge seems really quite sluggish. What sort of RPM are you pulling on takeoff?

It will be very interesting to hear what the boat weighs in at when you put it on the weight bridge. Ive often eyed off the one at the BP on eastlink (Melbourne), but never actually stopped to follow through.

Where are the inspection ports you are talking about?. The only thing like that I can see are the two holes on the corners of the engine cover. But they simply feed into where the bilge is anyway. I suspect im missing something.

Thanks guys. Look forward to hearing back

Dave

[newbienewb]

Wow....I can only dream of 4000 rpm on takeoff!!!!!. Lol. I can't even hit 3000.

Yeah I had a look in those inspection holes and dry as a bone :).

Out of interest do you have a tender/dinghy on your roof?

I have Neville whittleys number here. Might give him a ring. Thanks for the reminder!
Cheers

Dave


Sent from my iPhone using Tapatalk

[brett62]

I had the tender on davits on the swim platform. It makes on difference getting on the plane. I only carry it and the outboard when I am heading off to the islands. I carry it on the rack if I am going a fair distance and still don't have trouble getting on the plane.

You certainly have an issue with the motor.

Glad you don't have the water problem I have.

[newbienewb]

Hi All,

just wanted to check in and give an update to this long standing issue.

Over the last four weeks or so ive been tinkering around changing a few things.

1) Fuel system pressure is fine.
2) New distributor cap and rotor button
3) Rewired all wires to distributor (very corroded)
4) cleaned injectors.

I took it out on the water the other weekend, and the good news is the surging (which I suspect was the corroded wires to the coil), and the pinging, are both gone. This is great news.

However, the lack of RPM on takeoff is still persistent.

On the boat I have myself, my wife and our three young kids. I have a days worth of food and fishing gear along with a full water tank, and full fuel tank (about 150 and 250 respectively I think). However I still only manage 2900 at WOT.,

Engine is 5.7 MPI Horizon with about 400 hours. Bravo three the dual 20P props and a 2.00 ratio on the drive.

Compression on each cylinder is about 190 PSI, with the exception of one which is down at around 160

Im looking for any suggestions as to why I may be having issues hitting a good RPM on takeoff. I feel as though im starting to break the back of all these issues, but this one is really bugging me. With another family on the boat I need ot ask people to move down the front for launch........................a little embarrassing.

Look forward to any replies.

Dave

[snatchy]

Hi All,

just wanted to check in and give an update to this long standing issue.

Over the last four weeks or so ive been tinkering around changing a few things.

1) Fuel system pressure is fine.
2) New distributor cap and rotor button
3) Rewired all wires to distributor (very corroded)
4) cleaned injectors.

I took it out on the water the other weekend, and the good news is the surging (which I suspect was the corroded wires to the coil), and the pinging, are both gone. This is great news.

However, the lack of RPM on takeoff is still persistent.

On the boat I have myself, my wife and our three young kids. I have a days worth of food and fishing gear along with a full water tank, and full fuel tank (about 150 and 250 respectively I think). However I still only manage 2900 at WOT.,

Engine is 5.7 MPI Horizon with about 400 hours. Bravo three the dual 20P props and a 2.00 ratio on the drive.

Compression on each cylinder is about 190 PSI, with the exception of one which is down at around 160

Im looking for any suggestions as to why I may be having issues hitting a good RPM on takeoff. I feel as though im starting to break the back of all these issues, but this one is really bugging me. With another family on the boat I need ot ask people to move down the front for launch........................a little embarrassing.

Look forward to any replies.

Dave

Good luck working through the issues. You will get there eventually.

We once had one sparkplug that was partly broken internally and caused intermittent power and surging issues on our V6 MPI. Took a while to find it. If you haven't already (I couldn't see this in your posts), you could change all the plugs to eliminate them as an issue.
Corrosion in the distributor cap is common, but you have changed the cap I see.

Do you have smartcraft info displayed from your engine? It could help with diagnosing the issues. 2nd hand stuff is available these days

Have you had the engine computer hooked up to a Rinda scan tool to see if it has anything useful to say?

[scottar]

As above - make sure it is firing on all cylinders. Also make sure that the throttle is actually being actuated fully by the cable.

[juggernaut]

I had something similar happen to one of the 8.1S Mercruisers in my SeaRay a month back. Was doing a 70klm trip up the coast - dropped the revs back to pull in behind an island for a look - as I went to get back on the plane, my starboard engine would only rev to 3500 rpm and the ZF transmission on this engine sounded like it had blown. Engine idled fine and free revved fine. Did the next 50klms on the remaining motor as I thought the transmission had failed for some reason.

Even the Mercruiser tech couldn't find the problem when I got to my destination. With the suggestions from the ClubSeaRay forum I sorted the problem out - it turned out to be an ignition lead had some cracks in the insulation and was arcing across to the exhaust manifold when the motor was under load in gear and would drop a cylinder and therefore power and rpm and made the transmission sounded like it had a bag of marbles inside.

So my suggestion is to replace your spark plugs and ignition leads and hopefully watch the rpm come back.

[newbienewb]

Hi Guys,

I did buy a second hand rinda scan tool, however the software was so old in it that it wouldn't read my MEFI3, and the seller wouldn't help, so I logged a claim with ebay and returned it.

I have checked the throttle cable and butterfly on the throttle body, and indeed the butterfly does open all the way at WOT.

I changed the leads and plugs about 6 months ago for brand new ones, but didn't gap the plugs. I didn't think you even needed to do that these days.

Pulling my hair out pretty bad over this.

Dave

[Robg]

Have you checked for air leaks on the inlet manifold or any cracked vacuum lines if there are any, just a thought.

[Seppo BNE]

Certainly a tricky one! -- When replacing the distributor cap etc, was the timing checked to be OK?
Not sure on the design of risers/intakes on these, but, is there any chance of a restriction in the inlet/exhaust manifold?
Blocked air filter?, loose crap partially blocking the intake?, part of riser or something in the exhaust blocking the exhaust?
Does it rev up similarly with no load, and under load?

[MyWay]

did you had boat looked by any qualified mechanic yet ?
at least it could point you in the right direction to fix this problem

[newbienewb]

Hi Guys,

Sorry its taken me so long to get back to you. Busy time of year!.

Im quite sure there are no intake / exhaust blockages. I have had risers and manifolds off and checked. I have had exhaust Y pipe out fully and have confirmed no blockages.

There are also very few air hoses into the intake, and i have checked them all and confirmed no leaks.

Tomorrow i will be taking the boat out for a few baseline RPM tests, and i have a question about my timing before i do.

I'm not sure if i have my base timing set correctly. I put the engine into service mode by connecting a paperclip to points A and B on the DLC (this is the same thing that the mercruiser timing tool does). However neither my balancer or my timing cover have indicators to show 8 degrees. I have taken a video of my timing and post the youtube video below.


https://www.youtube.com/watch?v=6taMfWtgOvo

Can anyone tell me how to correctly find 8 degrees here????

Thanks guys.

Dave

[Gon Fishun]

Dial back timing light.

111858

[newbienewb]

Hi Gon Fishun,

Unfortunately my timing light is not that sophistimacated!

I dont have the ability to dial the timing on my light.

I measured the circumference of the balancer at 637mm.

From there i know that 637/360 = 1.769.

IE: Each 1.769mm is equal to 1 degree.

I got a piece of masking tape, drew TDC on it, and then measured 1.769 * 8 (degrees) = 14.155mm

IE: The 14.155mm mark on my tape equals 8 degrees.

In other words - i made my own timing tape - LOL.

The big assumption I have made is that the one single mark on the balancer is the TDC mark. A gent on another forum has suggested that this is infact the 8 degree mark, but i have to say im not convinced. Every motor ive ever worked on has a TDC mark on the balancer.

Thoughts?

Dave

[Gon Fishun]

Hi Gon Fishun,

Unfortunately my timing light is not that sophistimacated!

I dont have the ability to dial the timing on my light.

I measured the circumference of the balancer at 637mm.

From there i know that 637/360 = 1.769.

IE: Each 1.769mm is equal to 1 degree.

I got a piece of masking tape, drew TDC on it, and then measured 1.769 * 8 (degrees) = 14.155mm

IE: The 14.155mm mark on my tape equals 8 degrees.

In other words - i made my own timing tape - LOL.

The big assumption I have made is that the one single mark on the balancer is the TDC mark. A gent on another forum has suggested that this is infact the 8 degree mark, but i have to say im not convinced. Every motor ive ever worked on has a TDC mark on the balancer.

Thoughts?

Dave

All my experiences have been the line is TDC. We had dial back lights back then. I would take it as TDC and you can check after removing the no 1 spark plug. I think you have done this. The setting you now, by the video, looks good to me. I would not retard it all, if any thing advance it and listen to the motor. But don't go to far. Does the distributor have vacuum or mechanical advance or is it all electronic. If vac or mech and not working this will affect the power.

[newbienewb]

Hi Gon Fishun, i think ill take the mark to be zero. Based on that I have set the timing to 8 degrees using some home made timing tape. The dizzy has no vac advance. Id suggest all electronic.

So this morning we popped down to the bay and went for a squirt. Perfect morning for it. barely a breath of wind.

I did 6 runs with the 20P props, and then 6 runs with the 22P props.

Each run with the 20P props were within a poofteenth of each other.
TakeOff WOT = 2950 RPM
Cruising WOT (with boat trimmed up) = 5000 RPM
Top Speed was about 50 knots give or take.

Likewise each run with the 22P props were almost identical.
TakeOff WOT = 2750
Cruising WOT - 4900
Top Speed was about 55 knots give or take

No pinging at all, and great throttle response once up.

Top end seems fine, and im certainly reaching the 5000 RPM mark. I just seem to be lacking a few RPM's on takeoff. This video is as light as the boat will get. No water, half fuel and two people. Thats about it.

Youtube video of boat taking off and cruising at WOT.

https://www.youtube.com/watch?v=wuJVcmjo3JE

What are your thoughts?

Dave

[scottar]

If it's supposed to only hit 5000 RPM then there probably isn't that much wrong with it apart from being a big heavy boat. It simply means your props aren't slipping a whole lot during take off and the engine is having to wind up. IMO the take off looked normal.

[juggernaut]

Looks fine to me for a boat of that size. In relation to prop choice just make sure you choose the one to give you the required rpm at WOT.

[brett62]

Hi Gon Fishun, i think ill take the mark to be zero. Based on that I have set the timing to 8 degrees using some home made timing tape. The dizzy has no vac advance. Id suggest all electronic.

So this morning we popped down to the bay and went for a squirt. Perfect morning for it. barely a breath of wind.

I did 6 runs with the 20P props, and then 6 runs with the 22P props.

Each run with the 20P props were within a poofteenth of each other.
TakeOff WOT = 2950 RPM
Cruising WOT (with boat trimmed up) = 5000 RPM
Top Speed was about 50 knots give or take.

Likewise each run with the 22P props were almost identical.
TakeOff WOT = 2750
Cruising WOT - 4900
Top Speed was about 55 knots give or take

No pinging at all, and great throttle response once up.

Top end seems fine, and im certainly reaching the 5000 RPM mark. I just seem to be lacking a few RPM's on takeoff. This video is as light as the boat will get. No water, half fuel and two people. Thats about it.

Youtube video of boat taking off and cruising at WOT.

https://www.youtube.com/watch?v=wuJVcmjo3JE

What are your thoughts?

Dave


Hi Dave,

You are doing 50-55 knots ? Mate if you are pulling that speed there is nothing wrong with that. I get 35 knots WOT and we have the same boat with a 5.7l 300hp. Yours must be super charged. What speed are you doing at cruise which would be 3500 - 3800 RPM.

certainly agree with Scott as to the video, all looks good.

[scottar]

Hi Dave,

You are doing 50-55 knots ? Mate if you are pulling that speed there is nothing wrong with that. I get 35 knots WOT and we have the same boat with a 5.7l 300hp. Yours must be super charged. What speed are you doing at cruise which would be 3500 - 3800 RPM.

certainly agree with Scott as to the video, all looks good.

GPS speed or dream dial I wonder Brett ? If it's on GPS it is well quick for a rig that size.
Either way it gives you something to aim for with the new engine hey Lol

[gofishin]

...Each run with the 20P props were within a poofteenth of each other.

Cruising WOT (with boat trimmed up) = 5000 RPM
Top Speed was about 50 knots give or take....
...What are your thoughts?
That something's wrong with your GPS, speedo or glasses prescription Dave :) . Was it a GPS speed, or speedo? And was it knots or mph? Even if mph, still seems high.

That speed with a 20p prop at 5000rpm and 2.0 ratio leg is 'impossible' I reckon Dave.

Mid to high 30's maybe even 40 'knots' max at a guess without actually crunching the theoretical speed calcs.

And 55 knots.... nah. :)

Cheers
Brendon

[MyWay]

Hi Gon Fishun, i think ill take the mark to be zero. Based on that I have set the timing to 8 degrees using some home made timing tape. The dizzy has no vac advance. Id suggest all electronic.

So this morning we popped down to the bay and went for a squirt. Perfect morning for it. barely a breath of wind.

I did 6 runs with the 20P props, and then 6 runs with the 22P props.

Each run with the 20P props were within a poofteenth of each other.
TakeOff WOT = 2950 RPM
Cruising WOT (with boat trimmed up) = 5000 RPM
Top Speed was about 50 knots give or take.

Likewise each run with the 22P props were almost identical.
TakeOff WOT = 2750
Cruising WOT - 4900
Top Speed was about 55 knots give or take

No pinging at all, and great throttle response once up.

Top end seems fine, and im certainly reaching the 5000 RPM mark. I just seem to be lacking a few RPM's on takeoff. This video is as light as the boat will get. No water, half fuel and two people. Thats about it.

Youtube video of boat taking off and cruising at WOT.

https://www.youtube.com/watch?v=wuJVcmjo3JE

What are your thoughts?

Dave

nice
WOT at 5000 rpm is spot on
runs good and sounds even better
if you can cruise at 3400-3700 and hold on plain it is all sweet

[gofishin]

Just watched the video Dave, that hole shot is pretty good for a 7m Whitley that would be heavier than your 2t I reckon.

What is the max REC Rpm for that donk?

Theoretical speed is 5000 x 20" / (2.0 x 3.2808 x 200 x 1.852) = 41.1kn.

Allow 5% slip (might be more in reality) and your speed will actually be around 39kn....

To get to 50kn you would need around 500hp +/- Dave.
Cheers
Brendon

[brett62]

GPS speed or dream dial I wonder Brett ? If it's on GPS it is well quick for a rig that size.
Either way it gives you something to aim for with the new engine hey Lol

Scott re thinking the re-power after those figures. LOL

Brendon the weight of my boat when it hits the water is 3 ton and that's without people. You would certainly want serious HP to get to 50-55 knots. Don't think I would like the fuel bill either.

Dave's video shows it doing everything good.

[newbienewb]

Morning Guys!.

So a little more testing has confirmed what you chaps are all saying. Sorry if i confused anyone.

I installed an app on my iphone to show GPS speed, and indeed the speedo on the boat seems to be way out!. Is this a common thing??

Brendon your calcs are very accurate.

With the 22P props on the boat at about 4900 RPM WOT, i managed to top out at about 77km/h.

If i plug this into your calculation, allow 5% slip and convert to knots, i get 44.3 knots (which equals 78km/h). So, if i put my 20P props back on (which is my preferred), i should get a max theoretical speed of roughly 73km/h (assuming i reach 5000rpm).

Forgive my ignorrance (im no mathematician!), would you mind helping my understand that calculation?

5000 = RPM
20" = Prop pitch
2.0 = Assume this is outdrive ratio
1.852 = Conversion to knots
3.2808 = is this some sort of feet/meters conversion?
200 = This is confusing me.

The real test will now be to see how it performs with full gear and another family on it.

Im also now thinking id like to put a slightly larger camshaft in it :). Nothing wrong with a few extra ponies. :) Im looking at rebuilding the motor myself over the winter anyway. So might be a good opportunity.

Dave

[scottar]

I installed an app on my iphone to show GPS speed, and indeed the speedo on the boat seems to be way out!. Is this a common thing??



It's a pretty regular occurrence. Hence the dream dial reference. With your RPM's at take off, the thing to take into account is that marine engines, unlike cars, run only one gear ratio (no changing gears as you accelerate) so realistically it's like taking off from the lights in 4th to a point.

[newbienewb]

Dave inspection ports are a about in line with the back table mount. They give you access to your fresh water plumbing. Just need to roll the carpet back.

I hit the throttle to 4000rpm and that lifts me on to the plan in no time. I then back it off. I can get on the plan with out having to bring the leg all the way down also. I don't use the tabs at all until I am up and running and then I need to throw a little in due to the single screw throwing a chine down and this will change with speed.


Howdy Brett,

Just wanting to come back to your above comment if i can (and get input from any other board members).

The thing that is still bubbling away inside my is how you manage to get 4000 RPM on takeoff??. This is now the single thing thats making me "hang on" to this issue. What motor do you currently have?. Yesterday's testing certainly shows that the boat can get up on the plane, and hit top RPM, however this was a very controlled test.

If i were to throw my usual gear onboard along with my three small kids and wife, full water, full fuel, and our family friends (2 adults and 2 kids), i suspect i will have the same issue i always do which is still 2900 RPM and a loooooong time out of the hole (to the extent i need to distribute weight to the front). Only testing will tell - but im still hanging onto your 4000 rpm on takeoff.

@scottar - understand exactly what you are saying. And certainly understand the concept of the ratio's etc. My issues is that i just assumed id be able to pull more than 2900 RPM on takeoff. Perhaps im just expecting too much.!!!! :)

Christmas tomorrow people! - anyone got any new boaty toys coming? :)

Dave

[scottar]

Brett - was yours a duo prop set up like Dave's is ? Dave - did you ever look further into a foil (if my memory serves me correctly you didn't have one) ?

[gofishin]

... Brendon... would you mind helping my understand that calculation?

1.852 = Conversion to knots "yep"
3.2808 = is this some sort of feet/meters conversion? "yep, feet per meter"
200 = This is confusing me....

full conversion calculation the way I did it was; 5000 x 20” x 60min / (2 x 12 x 3.2808 x 1852) = knots

Grouping/reducing whole number conversion factors we get; 60 / (12 x 1852) = 1 / (200 x 1.852) … so that's where the 200 comes from. Just makes the equation smaller/easier and less typing :)

PS. Forget about the rpm on take off Dave, this doesn't mean much so long as she is getting up nicely - which your's is. You prob have near twice the blade area Brett does = bugger-all slip at take off = low revs in comparison while the torque is overcoming the "hump load" with minimal slip.

Yours is jumping on the plane now, all good! Check against max REC WOT, check again fully loaded. Maybe the 22p might be fine as a day prop unless really heavily loaded.

Merry Christmas :)

Cheers
Brendon

[brett62]

Howdy Brett,

Just wanting to come back to your above comment if i can (and get input from any other board members).

The thing that is still bubbling away inside my is how you manage to get 4000 RPM on takeoff??. This is now the single thing thats making me "hang on" to this issue. What motor do you currently have?. Yesterday's testing certainly shows that the boat can get up on the plane, and hit top RPM, however this was a very controlled test.



If i were to throw my usual gear onboard along with my three small kids and wife, full water, full fuel, and our family friends (2 adults and 2 kids), i suspect i will have the same issue i always do which is still 2900 RPM and a loooooong time out of the hole (to the extent i need to distribute weight to the front). Only testing will tell - but im still hanging onto your 4000 rpm on takeoff.

@scottar - understand exactly what you are saying. And certainly understand the concept of the ratio's etc. My issues is that i just assumed id be able to pull more than 2900 RPM on takeoff. Perhaps im just expecting too much.!!!! :)

Christmas tomorrow people! - anyone got any new boaty toys coming? :)

Dave

Merry Christmas Dave.

Mate I am running a single four blade prop on a Bravo 1 drive. The four blade is much better for getting on the plane than the 3 blade which is now the spare I carry. The motor is 5.7 L 300hp carby engine.

I purchased the boat secondhand and the previous owner had just replaced the engine and did say that he replaced with a performance engine which has a few extra upgrades such as cams, rockers and bearings. The motor is now out of the boat and was surprised as was Jim that she is a real 350 chev engine. Looking at your video and comparing to how quick I get out off the hole you are not far from what I do. The difference when fully loaded with my set up is very little. I don't have your top speed but have better low down performance. Remember you are over 3 ton in this boat with people added. They are not going to jump out on the plane like a ski boat. Also you should be doing your test with the boat in the configuration that you would normally run at. Put the weight in the boat and then do your testing and prop performance as things will change. I have set the boat up for the best cruise performance and also making sure I get to that recommended WOT RPM so the engine is not loading. If I wasn't replacing the motor with a diesel I would have played some more with props but Jim will have to start the science experiment again and I will also be using a Bravo 3 leg. Gear box ratios is something that comes into play also.

All the best and interested on your test results once you've completed your science experiment.

Brett

[newbienewb]

Hi guys.

For the first time in many years I'm lying here in bed awake before the kids, so thought I would take a moment to close this out.

Scottar - I did look into a foul (and in fact bought one off eBay that didn't fit the B3). I'm having trouble finding one for the B3??

Brendon - thanks for that, and I think you are right. It might be time to put this takeoff rpm thing to bed. I now have a better understanding as to why Brett might be getting higher rpm than me takeoff with peg gaps a little more slippage. Learn something new every day!!

I'm going to get my 20p props cleaned up and balanced. They are a little rough around the edges so that may also just tidy things up a little.

Brett - thanks for that. I don't suppose you have any detail of the cam in your motor? That's something I'm toying with. I have a pretty full auto workshop at my place and love rebuilding engines in my spare time. I'm planning on freshening up the Mercruiser over winter and a cam is on the cards. Just a small one. From what I can gather they are a pretty standard chev part....and theta single cam engine so not too pricey to do.

Did you ever get around to putting it on a weigh bridge?

Merry Christmas all. And sincerely thanks for all your help.

Dave


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[brett62]

Dave I will pulling the top of the motor very soon and I will see what it is running. Yes I did put the boat over the weigh bridge and the boat came in at 2.8 ton with no batteries, not full of fuel and water. It will be 3 ton easy when it hits the water. This is the real weight of our boats. I carry 320 litres of fuel and 150 litres of water. I estimated I had about 150 litres of fuel in the boat when I weighed it. Dave they are not light and that is good in my opinion as they push through the water and are not bouncing around kicking the shit out of ones self. Once again Dave your video is showing her running well. If you want more horse power and you are going to strip it down that will be the time to pimp the motor for sure. Having played with my boat I have found that the hull really likes to cruise at 23 -25 knots. That will be my goal with the re-power and hope I can get around that.

[gofishin]

No problems Dave. Been awake early too, but unfortunately that's from work issue's and not boating 'things' - they're the problems we don't mind losing sleep over aren't they?? :)

Merry Christmas to you guys, and all Ausfishers too!

Brett,
your new diesel will be great I am sure, 240hp 4cyl from memory? Don't be too concerned about the drop in HP (in comparison to petrol - especially in relation to cruise speed), as the mountains of torque is what provides the thrust you need. Top end speed will most likely drop, but you will love the economy and diesel grunt!

Although they were heavy dinosaurs in comparison to today's oilers, was involved with many a boat conversion to diesel in the 80's with my late father's business in PNG.

The improvements to the Volvo 30 and 40 series diesels (4 & 6cyl), and the release of the DuoProp legs in 85 led to many people jumping from petrol to diesel - coupled with the big trips/miles and hours the boats would do, increased reliability and the cheap cost of diesel in comparison (at that time).

Common boats for the single 6cyl variants (430kg plus leg from memory) were the 25 Bertie's & sister Nova & 23 & 24 Huntsman's (flybridge models), 23 & 24 Fjords (and some others who's brands escape me ATM - but most bigger and heavier than your Whittley .

HP was initially 134, then 155 with aftercooler, 165 with D/prop and then 200,. Wasn't involved after this when Volvo added superchargers and the HP went up and up.

The addition of the DP to the 165 made definite improvement to low speed manoeuvrability, faster cruise, better economy and slightly faster top end too from memory - but they were still a bit slow when loaded with lots of fuel for big trips etc (we are talking days/weeks, 100's of nm's, if not more, with prearranged fuel dumps etc, another reason for diesel as the local villagers outboards didn't run too well on diesel :) ).

It was the 200 DP that really provided improvements, and 'zip' ... but would still be considered slow by today's standards. 19-23kn cruise (@ approx 20-30 L/h from memory, depending on boat and loading ... but it was a long time ago... :)

Your 4cyl 240hp will go great :). I am sure you will be happy.

Cheers & Merry Xmas
Brendon

[scottar]

Scottar - I did look into a foil (and in fact bought one off eBay that didn't fit the B3). I'm having trouble finding one for the B3??



Permatrim have a model specific to the B3 listed on their website if you can't find one elsewhere. I ended up with one of these on my motor ( The version to suit an E-Tec) - seems to work - cost about $300. They are a bit different to a lot of the plastic type foils in that they rely entirely on the angle of the outdrive to set the amount of lift (no downturned surfaces) but against the SE Sport that I also tried, it didn't generate anywhere near the same amount of drag. You could if you have the time and inclination fabricate one yourself.

[newbienewb]

thanks Scottar,

Ill have to have a look into the permatrim. BCF seem to have a few but not sure if they are the right model for the B3, or just for outboards.

Finally got everything squared away yesterday, and heading down to the peninsula today!.

Dave