RPMS

[chaz64]

i have a 19' 1988 bayliner cobra with 125 force. according to the owners manual (and other people) i should be get at wot 4500 to 5500 rpms. right now im only getting 4500 rpms. i was told try a different pitch prop. i am using an aluminum 13half by 17 right now.any suggestions what size prop i should switch to to get higher rpms? thanks for any help you can give me!<br />chaz64

 

[bulldogs]

Re: RPMS

I have a 1990 19' bayliner cobra with a 120 force.My pitch prop is a aluminum 12 5/8 by 21 and i get 4500 to 5500. When the water is right and motor is trim up i get 50 to 60 mph. also i have been looking for a owners manual for my boat.I wonder if you manual for you 1988 would work for my 1990? bsalyer33@msn.com

 

[yensid]

Re: RPMS

I believe the general rule of thumb is you usually can get about 400rpms for every 2" increase, and vice versa. So you could probably go to a 19 or 21 pitch prop.

 

[JB]

Re: RPMS

You have the right idea, Yensid, but are going the wrong direction.<br /><br />Chaz, a 15" prop would get you more rpm, but unless that boat is a lot heavier than I think it should be, your 17 ought to get you to operating rpm. Make sure your engine is operating properly first. Then try a 15" prop.<br /><br />Red sky at night. . .<br />JB

 

[yensid]

Re: RPMS

<br /><br />It's not like I couldn't quickly look at http://www.boat-propellers.com or http://www.miwheel.com to confirm things. Ah well, thanks for catching that, JB!

 

[kev_79]

Re: RPMS

I agree with JB, that motor, with a 17 pitch, should push more than 4500 rpm's. Get the motor checked out before you go to buying props. Good luck

 

[sony2001]

Re: RPMS

chaz64 Your motor is at fault. Decarbonize,retime to 32 deg. BTDC then if you want I have a 21" prop for a 88 Force 125 hp. Your just like BULLDOG.