Fine Tuning-Raise Engine?

[Capt Jackrat]

Thanks for all the excellent applicable info on this site.

I have a 2004 16ft Sylvan Expedition Sport Aluminum V-Hull walk through bow rider with a 2003 90hp Yamaha 2-cycle(4500-5500rpm). It has smart tabs set on the #1 position and a 10hp trolling motor on the back as well. With a full tank and myself in the boat for the baseline:

1. 15P Yamaha prop WOT 5900/39mph
2. 17P Yahama prop WOT 4900/37mph

The eninge is mounted on the second hole down from the top. Do you think raising the engine one hole is worth it? The cavitation plate is approx 1in above v-hull.
Amidst all my reasearch on props I'm a little miffed by the large drop in rpm with the 17P. I certainly expected the 17P to be just right after my results with the 15P

 

[hwsiii]

Re: Fine Tuning-Raise Engine?

Jack, you must have two different models of their props.

H

 

[crb478]

Re: Fine Tuning-Raise Engine?

I would try raising it one hole, it is free and can be done and put back in one afternoon. As long as you are still pumping water and not cavating I would keep going up until you reach the point that you are doing one or the other, hopefully cavatating first. I would think that you could get 5500 out of the 17.

 

[Capt Jackrat]

Re: Fine Tuning-Raise Engine?

17P = H1-1317 with 3 holes in the front
15P = 131/2x15K

 

[countvlad]

Re: Fine Tuning-Raise Engine?

17P = H1-1317 with 3 holes in the front
15P = 131/2x15K

if with the 15 you;re turninf 5800-5900 i would stick with that and try to tweek the boat and motor around it... maybe go with a 16 in case you find a sweet spot that might increase your rpms...

 

[hwsiii]

Re: Fine Tuning-Raise Engine?

Jack that 15" prop is a Turning Point Hustler not a Yamaha, and it is very aggressive for an aluminum prop. You didn't give any numbers for the other one so I don't know about it.

H

 

[Capt Jackrat]

Re: Fine Tuning-Raise Engine?

Thanks again for all the help. Your right, the 15P is a Hustler. My memory is failing me. I raised the engine all the way up on the last hole and tried the Yamaha 17P again. I got 5500 RPM and 43 mph/gps. It just started to cavitate above 5500 RPM. Much smoother ride and an unexpected bonus of better sonar display throughout speed range. I think this case is almost closed. If I decided to purchase a 17P SS prop, would my numbers likely change. Any manufacturer reccomendations or other comments on my process? Thank you.

 

[hwsiii]

Re: Fine Tuning-Raise Engine?

Jack, that prop is showing such a low prop slip right now I wouldn't change anything, I doubt very seriously you would gain anything no matter what you changed to.


H

 

[countvlad]

Re: Fine Tuning-Raise Engine?

Thanks again for all the help. Your right, the 15P is a Hustler. My memory is failing me. I raised the engine all the way up on the last hole and tried the Yamaha 17P again. I got 5500 RPM and 43 mph/gps. It just started to cavitate above 5500 RPM. Much smoother ride and an unexpected bonus of better sonar display throughout speed range. I think this case is almost closed. If I decided to purchase a 17P SS prop, would my numbers likely change. Any manufacturer reccomendations or other comments on my process? Thank you.

if you're cavitating why not drop down a hole and see how it goes? might help