1990 85hp yamaha rpm

[MrBrownTrout]

I can't find anywhere that tells me what my rpm range is for my 85hp. Currently its on an 18' light aluminum boat, the tach shows it running at 5200 rpm and boat speed is around 39mph. I am running a stock aluminum 13.25x17 prop. Can anyone give me any ideas on how to improve my performance???

 

[MrBrownTrout]

Re: 1990 85hp yamaha rpm

Anyone have any advice on how to improve my performance???

 

[MrBrownTrout]

Re: 1990 85hp yamaha rpm

Does anyone know what the RPM range for this motor would be??????

 

[jim dozier]

Re: 1990 85hp yamaha rpm

Not my area of expertise, but since nobody's helpin. Guessing that your engine (like most 2-strokes) would probably want to see between 5000 and 5500 rpm so you are close now. 39 mph for an 85 hp engine doesn't sound bad. You could play around with the engine height on the transom or buy a jack plate and play around with the engine height and X dimension. Stainless steel prop might help. Do a search on these boards for engine height, jack plate, X dimension and you will probably find a lot of good discussions.

 

[Ray Neudecker]

Re: 1990 85hp yamaha rpm

Factory recommends 5500, but my preference is closer to 5800 for all around performance. Stainless props normally are more efficent. If there is a website for the brand of boat you are running you may find more speciic help on the setup.

 

[MrBrownTrout]

Re: 1990 85hp yamaha rpm

I have a 13 1/4 x 17 stainless prop. Its mounted on a trim & tilt plate, so it sets off the transom about 6 inches. The boat is a 18' westcoaster bayrunner.