WOT - 31mph@4100rpm HELP

[MrChuckFL]

New boat to me.

2001 Johnson 135

21ft Four Winns.

WOT gets me 4100 rpm at 31 mph. Seems like it takes forever to get on plane and anything less than 3500 and it loses plane.

Trimming up helps a little with planing but RPM doesn't change.

I think the prop is 14.5 x 17. It has a few dings and nicks.

Should I replace with the same prop or try something different.

 

[sabastianunf]

Re: WOT - 31mph@4100rpm HELP

We need to know what Rpm range the manufacturer reccomends to really know what prop will best but I would guess that you are below the reccomended rpm range for that motor. I would check the spark plugs, filter, timing and everything else to make sure it is running good. If it is then you could go with a lower pitch prop to get better hole shot - maybe a 15" pitch prop - which should increase rpm's by @ 400 but this may cost you a little on top end.

 

[Silvertip]

Re: WOT - 31mph@4100rpm HELP

That engine should be propped to allow it to run in the 5000 - 5500 RPM range. Something is dreadfully wrong. Make sure the tach is accurate and that you use GPS to check speed. Then make sure the engine is proper tune and engine mounting height set properly. Then and only then think about prop changes.