props for Yami 115 Four Stroke

[wastewaterguru]

Does anyone else have a Yamaha 115 four stroke on a 17 to 18 foot Lund. I have tried several different diameters and pitches and want to hear what other people have learned from their experiences.

I think I have a 13.75" Diam. x 15 pitch on it now cause my wife and I were doing some tubing and skiing last fall. Aslo have a 19 pitch that gives me a better top end (45 mph at 5300 rpm versus 36 at 5800 rpm for the 15 pitch).

I'm pretty happy with the performance but there are a lot of sizes I haven't tried and I have to be careful with the 15 pitch prop to keep my rpm's below the 5500 recommended by Yamaha. I would change this one, but a fat guy like me needs al the help he can get to get to the power band of the motor faster or I'd never get up behind that 115.

Any knowledge or advice for this motor/boat combo would be appreciated.

Lund 1700 Fisherman (17'5")Walkthrough
Yammi 115 Four Stroke.

Thanks,

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John K., a.k.a. wastewaterguru
Prior Lake, Minnesota

[This message has been edited by wastewaterguru (edited 03-08-2002).]

[Guest]

John,

I've got the same set-up (2001 Lund Fisherman with Yamaha 115 4-stroke). I currently have the "stock" aluminum 13.75 x 17 3-blade and get 40MPH at about 5400 RPM with a two person and gear load. Take my tach readings with a grain of salt because the stock tach is questionable. It likes to wave back and forth over a couple hundred RPM range even when I am holding RPM steady. I don't trust it at all. I plan on picking up a digital TinyTach ($40) before I get too crazy with the props.

The boat likes to plow unless the motor is trimmed way out and then I have problems with ventilation in corners. The low bow helps in rough water as the waves hit the V instead of smacking into the flat part of the bottom but it kills the speed on calmer water.

I'll start messing with props this year and was thinking of trying the Mercury TrophyPlus 4-blade or Laser II. My main goal is to get better bow lift with less engine trim and also eliminate the ventilation when turning. More speed would be great too but that's # 3 on the list. I assume hole shot would be better with the 4 blade.

The Yamaha manual gives an RPM range of 5000-6000 at WOT so I'm wondering where you saw the recommended 5500? Please advise. I'm also trying to get my hands on horsepower and torque curves to see where the optimum RPM actually is. So far, no luck.

Thanks and good luck,
Dave

[Rippinlip]

I have on older 90 horse Yamaha and the only thing I have to say is go Stainless in whatever pitch you decide, bought a Aluminum prop to make do for a back-up while I had my stainless re-balanced and oh my goodness what a difference. Lost hole-shot and top end while watching my tach go thru the red zone. I do believe the optimum range is around the 5500 RPM zone, I called a local dealer last year and that is what he said I should be running with load weight and trimmed out.

[wastewaterguru]

Thanks for the info guys.

Gunner1, let me know if you find the HP and torque curves. The 5500 is what the dealer recommended I target. Manual says 5000-6000.

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John K., a.k.a. wastewaterguru
Prior Lake, Minnesota

[oilguy]

1800 pro v full load of fuel and equipment.
motor came with 13X19 yam aluminum was able to get 42 @ 5200 and boat plowed. went to Solas 13.25X17 same performance able to run slightly more trim which helped plowing. went to 13.375X15 boat runs 39 @ 5800 (perfect) can run as much trim as I ever need. The Solas aluminum props tend to develop a cavitation spot about the size of a quarter near the middle of the blade after very few hours. They are inexpensive though. If you do much Canadian fishing (rocks) I'd suggest staying with the aluminum props, they could save you a lower unit. Would like to hear some more on this thread.

[Dan L]

I have a 115 Yamaha four stroke on a 1750 Crestliner Fishhawk. I tried a few different props and the one that worked best was the 19" Yamaha black painted stainless steel prop. My top end is 45 MPH and my top RPM is 5800. You can run that motor up to 6000 RPM's. I think you get the most out of your motor by getting close to the top of the RPM range. Remeber that if 2 props have the same pitch that doesn't mean that they will perform the same. Some props have a more aggressive blade.

[wastewaterguru]

I'll have my boat out Saturday in Redwing. I'll get a little more information on rpm vs. speed and trim and will give an update on Monday. Can't go all out on rhe river this time of year because of traffic, dead wood, ice, etc. but I should be able to get some info.

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John K., a.k.a. wastewaterguru
Prior Lake, Minnesota

[wastewaterguru]

I also had the same problems that gunner1 has. The Lund Fisherman owners that I know (4 total) all have yammi 115's and all have complained about air entrainment/cavitation when cornering. The way the setup is, you have to trim the motor out so far to lift the bow that there is not enough prop left in the water when trying to turn. I have found that I have to lower the trim in preparation for a high speed turn to prevent the cavitation. Does anyone know how to solve this problem? Is the motor mounted too high on the transom (is that even adjustable)?

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John K., a.k.a. wastewaterguru
Prior Lake, Minnesota

[oilguy]

It always gives me that warm fuzzy feeling to know that we (Lund owners) get to figure these bugs out. IMHO,if a few professional engineers were involved in design process, maybe things would be a little different. What the #%$^ we buy those red boats anyway!