Prop selection

[derekpfeiffer]

I am new to boating and just purchased an 89 cobalt w/ a 4.3 and alpha one drive. It came w/ two props one is a SS 3 blade that is 14.75 x 17 the other is a 4 blade alluminum that is a 15 x 16 I put my boat on the lake once just to check it out and make sure there were no major problems to take care of...and I had the SS one on it w/ three men in the boat...The boat seemed to have ok hole shot but only topped out at about 33-35mph...i was a little dissapointed but i was definitly running pretty high rpms so i don't think that's the right prop for the boat (and am hopping that there was no prolonged engine damage from the previous owner running that prop)...was wondering if the other one would be any better or not???

was wondering what you guys thought?

Thanks

 

[rndn]

Re: Prop selection

You need to provide more specific rpm's than just pretty high. You need to run your engine in the manufacturers suggested range in order to achieve a long life for your engine while enjoying peak performance and economy.

 

[mpsyamaha]

Re: Prop selection

those props should spin pretty close to the same rpm

 

[derekpfeiffer]

Re: Prop selection

Well i'm not sure that my tach is correct (I need to check it) but it said I was turning 5000 rpm which i've read that you want to be around 4500-4800 w/ this engine...Is this correct??

 

[rndn]

Re: Prop selection

If it's turning 5000 rpms you need to increase pitch. Approx 200 rpms for every 1 inch of pitch.