Tried 2 props, what do I try next?

[ivar]

Re: Tried 2 props, what do I try next?

Jarb,

I agree with Jamieat, a jack plate will let you fine tune to get the max rpm from the 19" Pro series you got. The 6" setback will not hurt either, letting the prop work in less disturbed water

Another prop to consider is the new Yamaha Reliance series, available in even pitches, like 18". These are supposed to give much of the same benefits as the pro series, while being slightly less aggressive.

Also , comparing pitches between different styles of propellers will often be kinda apples-oranges.

edit:
BTW, I've got a Yamarin too, a 5940 with F115. Using a 13x19" std aluminum for a max speed of 36 knots/6000 rpm.
As these Yamaha engines can use the same propellers from the 50HP 2-stroke up to 130HP, the engines often have different gear ratios. I also got a 60HP 2-stroke, with 28:12 gearing it also uses the same 13x19" prop.

 

[JARB]

Re: Tried 2 props, what do I try next?

Hello again!

Havent been here for a couple of a days. Good to see the thread is still alive. Thanks to all.

A limiting thing with the Yamaha 90 is that it uses the intermediate gear case. That gives a lot less propellers to choose from. Stevens Laser II is for the large V6 case so it wont fit my engine. Also the Reliance is only made to fit V6 cases..

A thing for you lucky Americans to consider, in stevens ad he says that the retail price for a new Laser II is 10000 Norwegian Crowns which is around 1900 US$. Thats why we Scandinavians try to buy our propellers in the US..

I have been more and more interested in a jackplate. It will maybe be a project for the winter.

Ben Paquin, Good to see that the Hustler made an improvement. I agree with you, I had expected you to gain more than 300 rpms. Does the Hustler have a lot of cupping? I myself was out in kinda rough weather yesterday. The Powertech ventilated quite easily in the high waves. Convinced me even more that a "Pro Series" style prop with good grip is what I need.

 

[Ben Paquin]

Re: Tried 2 props, what do I try next?

Ben Paquin, Good to see that the Hustler made an improvement. I agree with you, I had expected you to gain more than 300 rpms. Does the Hustler have a lot of cupping? I myself was out in kinda rough weather yesterday. The Powertech ventilated quite easily in the high waves. Convinced me even more that a "Pro Series" style prop with good grip is what I need.

Yeah the Hustler is well cupped. It is made to copy a performance Stainless profile but in Aluminum. However there must be something wrong my my engine or my peak HP is made at a low RPM. I tried a 17" pitch Hustler and my RPM went up to 5100rpm and I lost .6mph. I have about the same acceleration.
Seems like my engine is reluctant to go over 5K.

 

[ivar]

Re: Tried 2 props, what do I try next?

Ben,
could be that your tach is reading low.

JARB,
In the pdf file here, there's a 3- and 4-blade 18" for the intermediate gearcase: Seems like its in the "performance" series, not Reliance...
http://www.yamaha-motor.com/outboard/powermatched/propeller.aspx

One other option is to get in touch with Winrace propellers in Arendal, Norway. Olle Terjesen is a propeller guru, and can most probably rework/add cup to the powertech prop you got , to bring down r's a little and make it better suited for your application.

 

[stevens]

Re: Tried 2 props, what do I try next?

I second Ivar's suggestion about having your current prop reworked - probably AFTER you get that jackplate, if you're getting one.

If you decide to have the prop worked on, I understand there is also a very competent shop in Sweden for this: http://www.propellertrim.se/ That would save you from sending the prop across country borders and incurring freight & VAT each way.

Edit: Just came across your discussion on the same topic at www.fendern.se and see that you already know about your local shop. Good luck in your quest for speed. Please let us all know how it works out in the end....

 

[Ben Paquin]

Re: Tried 2 props, what do I try next?

Ben,
could be that your tach is reading low.

Unlikely. The RPM and pitch with 12% slip matches the speed perfectly.
The engine sounds like it's a bit low on RPM too. The tach is Yamaha and setup correctly.

Maybe it's normal the Yamaha 115 makes peak HP around 5000rpm, or maybe I'm running lean (the carb hasn't been rebuilt in a while). Any prop that let me go above that will reduce my possible top speed.

 

[ivar]

Re: Tried 2 props, what do I try next?

the 115 is listed at 115HP/5000 in the specs. Power falls off above that, but usually don't start to fall off that soon... I'd think it should be able to pull a couple 100 r's more..

 

[JARB]

Re: Tried 2 props, what do I try next?

Hello again!

Ben, my 90 is also said to produce peak power at 5000 rpm but my feeling is that most of the power is still there at 5900 rpm, although max rpm is said to be 5500 rpm. Should be very interesting to see a power/torque-curve of the engine, anyone know where to find it?

It sounds like your engine is restricted in some way from leaving full power. Lighter boat than me with more power being slower.. I have heard of a boat same as mine, over-powered with a Yamaha 115 with standard prop and engine height going close to 50 mph. Maybe it is time to check your carbs, fuel supply and ignition.

Ivar, In Sweden we have a boat magazine called "b?tnytt", maybe you know about it. A couple of issues ago they did a propeller comparison test on a sligthly larger and heavier boat than mine with a Yamaha F100. In that test the 18" 3-blade Performance prop only revved 100 more rpm?s than the 19" Pro and the 18" 4-blade revved same as the Pro. So I think they both will be to big for me.

Stevens, Yes it could be a good idea to modify my Power Tech SCD3 prop. The propshop you refered to use to have discounts on propjobs in the winter so I am thinking of contacting them to see what they say. Took some pics yesterday at full speed. When running the boat it feels bow heavy but the pictures indicates a pretty good ride I think. Please comment!

 

[Ben Paquin]

Re: Tried 2 props, what do I try next?



I don't know. I can't hear my engine misfire at anything over 1500rpm. At idle it does misfire a bit however I can troll at 3mph for an hour without having foul up issues. Also the plugs show no sign of being lean whatsoever. If anything they are wet which would indicate a rich idle and/or misfiring. Also I have no sign of detonation. My old plugs were perfect when I replaced them.

I have a video of me fooling around in the boat. Maybe it would give you guys an idea if things are sounding and looking normal. I think I have a very good holeshot. Takes just a few seconds to reach 30 mph due to the light hull. I think it's the hull that is just too inefficient. I'm trying to find a good hull with a bad engine to make a the swap.

 

[JARB]

Re: Tried 2 props, what do I try next?

Hello Again!

Here is a small update on my best-prop-finding-project. I have know ran a Stiletto Advantage 1 13,25" X 17" propeller. The boat had been in winter layup for a couple of weeks but I was so curios to test it that I put it into the water. Winter is early this year in Sweden so I had to break some ice to find open water.

This is the best prop that I have tried so far. It has superior grip and even though I have the engine mounted high it rarely ventilates. The top speed was 43,5 mph at 5100 rpm fully trimmed up. This indicates a slip of minus 6% which in theory is impossible. I have read that the Stilettos usually gets very low slip-figures due to the cupping and progressive pitch but I had expected the slip to be around zero, not negative. 5100 rpms is a little on the low side and the acceleration is not as quick as with the PowerTech SCD3.

If speed and slip does not change a 16" Stiletto would have been perfect giving me a rpm of 5400. Sadly it is not made in 16", the next step down is 15" and that would propably give me a too high rpm. The Stiletto is definately a keeper and it has a blade design that gives me the charcteristics I search for. Maybe I should let a prop shop work it to get the revs up a bit or maybe I should get a jack plate, anyway I have the winter to decide what to do.. Any suggestions folks?

Happy holidays from Sweden!