omc 4.3 best prop size

[proshine43]

Hello to all, i have a 1990. 18' galaxie, 4.3 omc cobra, with a 14 x 19 prop. I can get 38 mph at 3900 rpms wot. The manual says 4200-4400 rpm range is best. Which prop would you recommend? Thanks for your help

 

[bruceb58]

Re: omc 4.3 best prop size

You may want to first make sure that it isn't your engine that is keeping you from achieving full RPM. Have you checked your timing, dwell and fuel filters? How old is the fuel?

What is your experience with this boat?

You running at sea level?

 

[proshine43]

Re: omc 4.3 best prop size

Thanks for your quick reply, it is timed at 1 degree btdc, filters are new. First time on boat. And about 1000 ft above sea level. Thanks.

 

[ohioriverat]

Re: omc 4.3 best prop size

Yeah^^^ I have a 1992 19' glastron(heavy boat) with a 21 pitch ss prop and i reach 4500 rpms wot, sorry i can't tell you how fast it runs but i would say mid 40's

 

[bruceb58]

Re: omc 4.3 best prop size

Thanks for your quick reply, it is timed at 1 degree btdc, filters are new. First time on boat. And about 1000 ft above sea level. Thanks.

1? BTDC is way to retarded and that will affect your topend. You need to set it to 6 at idle with a max of 18? at 3200 RPM.

You should use an advance timing light or some timing tape to see what your maximum advance is. If the centrifugal weights in your distributor are stuck and not allowing full advance, that can also cause a problem

 

[bruceb58]

Re: omc 4.3 best prop size

What is your dwell at? Age of fuel? Condition of carb? Any backfiring through carb when you accelerate?

I see you are close by me. Where did you take your boat to?

 

[proshine43]

Re: omc 4.3 best prop size

I took it to lake piru. My next trip is silverwood lake.