Prop Diameter

rpeecee

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I recently struck a rock with my 1996 Tournament powered with 1996 Saltwater Series 2 Yamaha 150 2 Stroke. Upon inspection, the prop is a 13 3/4 17 pitch. Using all the online stores to replace it, it seems that that diameter isn't recommended. I bought the boat used and have never been impressed with the overall speed and find that the rpms increase at full throttle, but there is no increase in speed, just in rpm and noise. I plan on keeping the 17 pitch but am thinking that I need a larger diameter. I am thinking 14.25. I understand that larger diameter would usually decrease speed and increase thrust, but could it be that the smaller diameter just spins ""freely" in the wash after a certain rpm. Honestly a bit clueless and am just guessing. Any thoughts would be greatly appreciated before spending 500 or so to find out. Thanks!
 
I'll check my mother's for a comparison - she has the same boat/engine.

BUT... you may very well simply have an old hub that is slipping based on what you wrote. That would be a much more likely scenario based on the info given.
 
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Interesting. I never thought of that. It does well pulling up my son wakeboarding so I never considered a slipping hub. It may very well be the original prop and I will most likely replace with same. I did once try a 14.5 x 17 and it was definitely NOT correct. Thank you so much for the reply.
 
It does well pulling up my son wakeboarding so I never considered a slipping hub.
Hmmm... well that new info, it puts doubt on a slipping hub. But then... it depends on how heavy he is and how hard on the throttle you're going.

Is it a Yamah prop? Has a stamp of "17M" on it?

Is the prop in perfect shape?

What type of RPM's can you get to going WOT and trimmed up till no more speed or the prop ventilates? Speed at that point?