Lifting engine

[ovakil]

I have just read on another article about engine height,where you should be able to see cavitation plate while cruising.
As I've noticed my boat (22 ft coxcraft pantera)being a bit heavy at the back.
Going to check that next time I go out.
Also was looking at putting trim tabs on,but thought I would need engine at correct height to get full use of them,as a guy told me that boat porpoises a bit


My problem with lifting motor higher is the steering shaft going through the pod,see pictures.
Any advice how to fix remedy.
Cheers

[FNQCairns]

Looks like a dodgee brothers setup to me:( at least in that photo. With that amount of setback you may even end up 3 inches higher, be warned the boat will then fly, use less fuel, trim, stop proposing and have lighter steering but it will not do ski type turns any more.

Strictly you need to run a straight edge or string line from the bottom of the hull all the way back to the cav/vent plate then fit the engine so it is near 3 inches higher (might even end up 5!!!) than the the line/edge then test run.

cheers fnq

[ovakil]

Did some measuring,ran a straight edge from bottom of V to cavitation plate,the plate 90mm above.In between front of plate & stern of boat (where transducer is) 870mm.
Does this help?
Also if going higher,steering can sit above pod,or cut a channel in pod.
Cheers

[Chimo]

looks like you could go up 4 holes fairly easily but you sure have a hassle with the steering. Does a 4 hole lift get your steering over the top of the pod?

Man that pod is the pits re the steering, maybe it needs a a cut and shut.:-/

FNQ sured called it when he suggested dodgee bros were involved. Really makes it hard to fine tune motor / boat setup.:-[

Trim tabs would certainly help and if their installed correctly ie not too low and won't add drag and they actually will lift the bum even when they are up.

Look at Lencos as they are simple to instal with no hydraulic oil even if you do need to cut holes in the "marlin board" step.

Cheers
Chimo

[ovakil]

Motor is in top hole,4 more holes down.If I was to put motor on bottom hole,steering would just clear pod.
Is steering easy to take off & on?As I probably just cut the pod out anyway,as later (couple of years) want to replace motor.Don't want to have same trouble again.
Cheers

[Chimo]

Go for it and see what a difference you get.

C

[FNQCairns]

Does look like some room to move, although that pic without the engine leg and keel line being at 90deg it's hard to tell for sure. Was your measurement with the leg vertical?

With the leg at 90degto the keel line the rule of thumb is the cav plate needs to be 1 inch higher than the keel line for every 1 foot of setback, setback will be the distance measured from the transom to the leading edge of the leg.

You may need to then go another hole higher, 2 holes if it is a fast boat but for a test run the rule is a good starting point.

cheers fnq

[ovakil]

Yes I trimmed down motor all the way down for measurement.
How many cm to a foot ?
Any fiberglasser's here as well,that would do this type of work.I would have steering off for it to be done.
No it's not a fast speed boat
Cheers

[FNQCairns]

Oh Ok, Nice boat! I am going to do an about face as that's a lot of hull in the water and advise to go up 1 hole only then test, then repeat etc you will know your as high as possible (if not there already?)when at fast cruising speed turns (the tightest you sensibly do in typical use) the ventilation will not be bad enough to cause any strange handling characteristics like a loss of drive that might call for a correction at the wheel etc.

cheers fnq

PS 305mm to a foot.

[Angla]

That certainly looks like a dodgy job but sounds like good advice so far re motor height.

I always thought porpoising was due to being trimmed too high. Just pull the motor back in until it stops. You might be saying that your boat setup does this with the motor trimmed all the way in. Is that a fair statement

Chris

[Chimo]

FNQ from what I remember of those hull they were not a real heavy boat but I guess it depends who of the many mobs that used the mould layed it up.

Ovakill what is the weight, from the trailer it looks to be less than 2000kgs?

Cheers
Chimo

[FNQCairns]

Hi Chimo yeah I just noticed the make and length was in the first post, are they over width? It's top speed will tell all, if only around 60-65km/h it's not going to get the bow lift it needs to go high with the engine, it will probably blow out first, also the yaw on turns with setback can introduce air that makes going higher problematic.

Interesting setup though.

cheers fnq

[ovakil]

Porpoises while I have been driving.So I've been told:-/.(I haven't had that much experience around boat's).
When I take off,motor is trimmed all way in,when on the plane I trim motor up till I see not much spray coming up from motor.Does this make sense.
Can take someone for a run who has some experience,to make sure I'm going about this the right way.(hint chimo)
Unsure of exact weight.I'm sure it's under 2000kg,that's what trailer is rated I think.
Generally sitting on 3800 rpm doing about 35 mph.

[Chimo]

Ovakill

If your doing 35 mph / 56 km at 3800 it sounds like the rig will get up to around 45mph / 70km at 5500rpm.

As a retired GOM more than happy to help if I can.
Where does the boat live? PM if it suits you.

Cheers
Chimo

[Angla]

In my boat I go full throttle and then trim up until the motor revs go over 5500 (max rated revs for my motor) then I back off a little and keep trimming up until it starts to cavitate( you hear the revs pick up and see the speed start to drop) I then drop the motor back down a touch until you feel the grip from the prop again and make sure the revs are under 5500. Spray from the motor is not a factor to look at as you are looking forwards at what you will run over.

You get to know the sweet spot as my trim gauge says 2.7 or 2.8 on glass conditions.

Chris

[FNQCairns]

Proposing is indicative of an engine too low and/or overproped, if you can post your engine brand and hp, maximum speed at what rpm + the pitch of propeller we might be able to see a little deeper as to why, with luck.

cheers fnq

[Spaniard_King]

take the hydraulic fittings off and unscreww the cylinder off the engine.. (posibly a grub screw securing the ram to the engione as well, to stop it from unscrewing)

There is a guy at Jacobs well who will modify the engine/transom setup if required
He has all the gear to do the job correctly and knows his sh!t

Should get major performace increase when thet setup is right.

[ovakil]

Proposing is indicative of an engine too low and/or overproped, if you can post your engine brand and hp, maximum speed at what rpm + the pitch of propeller we might be able to see a little deeper as to why, with luck.

cheers fnq

I have a 15" 4 blade solas stainless prop,1996 175 mariner,did rev to about 5800rpm can't remember speed.
I did have a 19" prop which apparently stuffed power head up,I got it rebuilt & spoke to solas,which they recommended 4 blade.
Cheers

[FNQCairns]

1000 2000 3000 4000 4500 5000 5500 5800

11.5 23.0 34.5 46.0 51.7 57.5 63.2 66.7


That's good if you are reaching 5800 and have a 4 blade you can all but discount gobs of slip as a contributing factor towardyour proposing, need to raise the engine a hole and test IMO.

Above is the rpm and speed (km/h) you should be seeing if it helps, I used a gear ratio of 1.75 (hope that's right?) and 10% slip so all speeds due to the low slip I factored may be a little high so consider them best case with that prop.

The 4 blade will usually allow a little more height than a 3 blade, interested to hear if you ever lift it, what result you end up with.

cheers fnq

[ovakil]

I'm looking into it know,need to get steering shaft area cut out & glassed,then I can adjust height far easier.
Another project to my list:-/,but wife insist a smoother ride.Can't argue as she put's the petrol in.
Also looking into Lenco trim tabs as Chimo suggested.
Cheers.

[FNQCairns]

It's a right shame you will need to get the glass work done to lift the engine, if you find you can go up a few holes, the boat should trim better so may negate the need for tabs to some degree compared to now but regardless they will still be a worthy addition.

cheers fnq

[Chimo]

Hi FNQ

Those Panteras have a lot of side (not to mention the clears) and tend to lead with their shoulder and OKs is the same so being able to stand it up straight so the bow does some work is the main benefit of tabs. There may be a little bum lift too as I found with the Vag. They can't hurt and most of us with them would not be without them.

There are a couple of options for the glass work thats needed and no doubt OK will work it out from the options he has. eg Spaniard King

Cheers
Chimo

[ovakil]

Boat is booked in a couple of weeks,modifying pod,adding a wedge,lifting engine 2 holes,test run may go up another hole.
Should I have trim tabs installed before testing?
Cheers.

[Chimo]

Hi Ovakil

IMHO once you have fitted trim tabs (Lencos would be my pick) you will wonder how you did with ot them.

Many people on here have commented that pretty well every mono over about 5 m benefits from them.

If Geo is doing the work why not fit them at the same time as you do the other work as you will fit them sooner than later anyhow. Then you can see if there is any lift from them, even when they are in the up position; and this will possibly impact on the engine lift and its final position.

Cheers
Chimo

[ovakil]

Geo didn't get back to me.I ended up buying a set of bennet's.They had an old stock item from a show at a big discount.Couldn't let that one go.
Cheers Steve.

[ovakil]

Quick update,boat has been taken to be fixed,plan is lift engine 2 holes,take for a run.Then decide if it needs to go up again.
Cheers Steve.

[ovakil]

What a difference it has made!Can't praise the guy enough.Took it for a run,got onto plane easier without wheel standing.We did some tight turns he just heard a bit of cavitation so we left engine at that height.Took it to full speed 5500 rpm at about 45mph on speedo.Adam told me trim motor down a bit,I felt boat slow down a bit,which he told me that was about where the old set up was.
Neat job on the glassing.He even had the time to show me driving boat on/off trailer a few times.

[Spaniard_King]

Good to hear Steve :)

[dnej]

Steve, who did the glassing in the end.How many holes did you go up? What degree is on the wedge?What did it cost?
David

[Chimo]

Hi Steve

Glad you got a good result, Work looks neat too.

Cheers
Chimo

[ovakil]

Steve, who did the glassing in the end.How many holes did you go up? What degree is on the wedge?What did it cost?
David

Adam 0404050310,Jacobs Well
Went up 2 holes,
5' on wedge
$600 all up.,including re routing cables higher up pod so water can't enter pod.Was having trouble with that as well.
Have a look at photo's at start of thread,that'll give you an idea.