Need prop pitch help with 18'cc sea pro.

[seapro_stevo]

I have a 2004 18' cc sea pro(equivalent to new18'seaboss) with a yamaha
115 four stroke. When i got the boat it had a 13 1/4 x 17 aluminum k series prop that turned 6200 rpm with full tank and 1 person trimmed all the way up. The prop was slightly bent so i went to a stainless steel stiletto 13 1/4 x 17. Now it will only turn 5800 with full tank and one person. Not bad except that is trimmed as far up as i can without ventalting. How are you supposed to test the max rpm of your prop? If i have it trimmed just right so it doesnt porpoise running at 4500 rpm and give it full throttle it will only hit 5300 rpm. If i trim it up real high it will rise to 5800 rpm. Am i over proped?





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[micel]

Re: Need prop pitch help with 18'cc sea pro.

Under proped!I'd try a 19" 4 blade,and go from there!

 

[seapro_stevo]

Re: Need prop pitch help with 18'cc sea pro.

Under proped!I'd try a 19" 4 blade,and go from there!

how do you figure?

 

[boling]

Re: Need prop pitch help with 18'cc sea pro.

I've got an '05 with a 115hp 2 stroke. I can turn about 5800 trimmed out with a 17 pitch rapture SS.

As I understand, go full throttle, then trim up till the rpms go up without the speed increasing, then trim down a touch. Now look at the tach.

Not sure what your engine wants as a WOT (likely between 5000-6000, check your book). You want to make sure that with an average load, you can hit that the upper portion of your range.

Quite possible you are set up pretty good now.

It's expected to drop rpm's when moving from al. to ss., even in the same pitch(blades flex less with ss)

Chris

 

[micel]

Re: Need prop pitch help with 18'cc sea pro.

Im just going by the figures you gave using aluminum prop,I have no experience with your ss.I'd try the power-tech 4 blade 19"then if thats too much they will take it back and they will analyse data and send you another.

 

[Manipulator]

Re: Need prop pitch help with 18'cc sea pro.

Going up in pitch you will lose RPM. If you're at 17 pitch going down to SS 16 should gain you 200 more RPM. Aluminum flexes, SS does not. Could explain the difference in RPM.