PROP PROBLEMS

[kahoona]

Hi all,

I have a 1991 200 HP Mercury with 240hrs pushing a 6.8 m tiny, it has a 19 P. five blade prop which in my mind is not the best combination for this outfit. ??? The fuel consumption is almost double that of my mates which both run 200 Yamaha's, one is a 21 foot savage bluefin (fibreglass) the other is a 25 foot 6 ml plate alloy and quite heavy boat. :'( They both run a 19 P. 3 blade prop and their boat speeds are 40 and 37 knots respectively.
My boat will only get up to about 33 knots and the engine only revs out to between 52 and 5300 revs.
I have been told the five blade prop will get you out of the hole quicker but sacrifices top speed, which equals fuel consumption. http://www.ausfish.com.au/chat/images/smilies/cwm15.gif
The hull shape gives the appearance that it should be quite quick across the water, it has a fine entry running into a deep V and flattening out at the stern.
Would anyone know where I could find a three blade 19 P. vengeance or something similar to see if this is going to be the solution.
I would greatly appreciate the help anyone can give me to fix my problem. ;D
Many thanks,
Paul. 8)

[Big_Muddie]

Hi Paul.


I can't advise you on the choice of prop but someone who can is Steve Evans from Solas Propellers in Maroochydore.

He provides great service and excellent advice.

I have bought props through him and he has gone to the trouble of water testing several props on my boat before making a recommendation.

His business phone number is (07) 5479 4898.

His website is www.solas.com.au

I have seen other names mentioned on this board - at least one in Brisbane. I can't recall who it was but I'm sure it will turn up.

Good luck!

[rwells9999]

Hi Paul,
Yes Solas are excelant, Iv'e had geat service and turnaround from them.

Robin

[Kerry]

Comparing fuel comsumption between different motor brands is probably not a good guide.

For normal boating use I've never seen why this "getting out of the hole" should really be an issue. Some might say they need it for crossing bars but if one is getting the right revs relative to the correct HP for the boat then it all could become rather academic.

A 5 blade prop ??? isn't really something one sees on every second boat and one could ask the question why as if they were suitable for general use then manufacturers would have made them as standard.

Without a benchmark to work too (standard Merc prop for that boat/motor combo) then it's difficult to compare if certain props are better than others for the purpose.

Only 5300 rpm wot ??? doesn't mean much without knowing the max wot for that engine. If it's 5500 then that close (sort of, but not close enough for me), if it's 6000 then 5300 is absolutely no where near enough.

One of the problems in all this is finding/begging/borrowing/stealing enough different props over a time frame to really find out.


Cheers, Kerry.

[CHRIS_aka_GWH]

might sound obvious but your mates aren't running 4stroke / injected engines.

Also have you played with the trim on the plane? I only run a 50hp Merc on a 4.75m boat but I've found adjustment of my trim on the plane provides a definite increased speed (up to 3mph) or fuel saving if I throttle back.

chris

[kahoona]

Thanks fellas for all the input.
I have had a hard time trying to find people with the same sort of motor to test a prop, so I think the best approach may be the professional one.
Thanks again,
Paul.

[Big_Kev]

To find a solution to your problem would be to sell the Merc and put a new Yammie on the back .
Cheers Reel Hard

[Kerry]

Thanks fellas for all the input.
I have had a hard time trying to find people with the same sort of motor to test a prop, so I think the best approach may be the professional one.


Don't need the same sort of motor just the right prop and you have mates ??? with yammies :o so pinch there's, they'll (should) fit.

Cheers, Kerry.

[Fitzy]

and you have mates # ??? with yammies #:o so pinch there's, they'll (should) fit.

Cheers, Kerry.

Good point Kerry, however they should fit IF you get the right bushes for them. The mates probably wont have the right bushes to suit a Merc if they're running yammy props on yammy donks.
I tried a few Merc props while working out the best to suit 80 Yammy 4 banger & had this problem.

Not 100% sure with the mentioned motor sizes tho, could fit straight on.

Cheers,

Kerry

[Kerry]

Fitzy, standard merc and yammie (at least in the mid HP range) props were directly interchangable but that was pre 4S days so maybe they are different now?

Still wouldn't like to run those merc props on yammie except for testing thou as the thru hub exhaust area (on the ones I tried) of the merc props was about 20% less than the yammie props.

Not sure if that would have any affect on back pressure etc but good enough to get a feel for prop size.

Cheers, Kerry.

[Ron_Collins]

Hi Paul

You've posted an interesting question and from the replies, I'd rate your problem as a "work in progress" issue.

I'm not an outboard motor mechanic or specialist, but have clocked up a "few" hours on the water in a variety of rigs - including some in the 6m-plus size range.

My suggested solution to you is to discuss the problem with the outboard distributor. Murray Linn is the Queensland manager of Mercury Marine and he can be contacted at their Woodridge office on 3208 5333.

There is a massive number of issues that need to be taken into account when trying to come up with a solution to your specific problem: Total weight of your boat, motor, trailer, fully rigged and fueled etc, etc and on the water for a fishing trip; design of your boat and the degrees of angles etc; proportion of your boat still in the water (and therefore causing friction) when you're underway at normal working speed; best operating trim (probably one of the most important); quality of the manufacturing job on your boat, ie was it home made, professionally made, plate, pressed and so on and on - to name a few.

I happen to think that getting your boat out of the "hole" effectively and efficiently is very important. (That's especially so for boats used offshore, and I'd guess yours spends a bit of time there.)

The reason for this is that there is nothing worse than trying to look over a dash or through a windscreen when your boat is at a riduculous angle to the horizon. It also makes it very, very difficult to make a quick and calculated decision in what can be, or what can turn into, dangerous sea conditions that impact on your boat's efficiency and safety characteristics.

Hope that helps your quest. If you still strike problems, please get back to me and we'll assist you in any way we can personally and through Bush N Beach Fishing. - Ron Collins, Ed.

[Ron_Collins]

Hi Paul

You've posted an interesting question and from the replies, I'd rate your problem as a "work in progress" issue.

I'm not an outboard motor mechanic or specialist, but have clocked up a "few" hours on the water in a variety of rigs - including some in the 6m-plus size range.

My suggested solution to you is to discuss the problem with the outboard distributor. Murray Linn is the Queensland manager of Mercury Marine and he can be contacted at their Woodridge office on 3208 5333.

There is a massive number of issues that need to be taken into account when trying to come up with a solution to your specific problem: Total weight of your boat, motor, trailer, fully rigged and fueled etc, etc and on the water for a fishing trip; design of your boat and the degrees of angles etc; proportion of your boat still in the water (and therefore causing friction) when you're underway at normal working speed; best operating trim (probably one of the most important); quality of the manufacturing job on your boat, ie was it home made, professionally made, plate, pressed and so on and on - to name a few.

I happen to think that getting your boat out of the "hole" effectively and efficiently is very important. (That's especially so for boats used offshore, and I'd guess yours spends a bit of time there.)

The reason for this is that there is nothing worse than trying to look over a dash or through a windscreen when your boat is at a riduculous angle to the horizon. It also makes it very, very difficult to make a quick and calculated decision in what can be, or what can turn into, dangerous sea conditions that impact on your boat's efficiency and safety characteristics.

Hope that helps your quest. If you still strike problems, please get back to me and we'll assist you in any way we can personally and through Bush N Beach Fishing. - Ron Collins, Ed.

[kahoona]

Hi all,
Thanks to Ron, Fitzy and all ;) who took the time to reply to my problem, it has given me a variety of different avenues to chase, and I'm sure with this many options i will be able to find a solution. :)
wishing you all fair winds, calm seas and good fishing,
Paul 8)

[webby]

Hi Paul, Long time no hear or see, will give u a call and arrange a trip, hope you excursion to moreton was better then the weather.
Finally got that shirt, so im set for the rosebowl this year.
Told you to change to glass instead of that giant tinny ;D
regards