dellsboater
Petty Officer 2nd Class
- Joined
- Nov 19, 2010
- Messages
- 193
1988 Liberator with OMC RPM and Prop question
I have a 1988 OMC Cobra Drive, 350 Chevrolet. It Idles fine and the tach reads 800-1000 RPM's.
At 35 MPH at plane it reads 4000 RPMS, but at WOT it Reads 5900 RPM's at 52 MPH. That tells me I should run a 25 pitch prop not the SS 21 I have now. Taking into account each prop pitch increase lowers RPM's by 200, that should put me at 5100 RPM's and more top end. The specs say it should run at 4600-5200 RPM's.
So It seems either I am under proped, or my tach is faulty. I did restore this and replace the tach, but the idle does seem correct. It runs about 140 degrees at 35, but does go to 180 when running wide open and doing some quick turns. It does come back down to the 140 range when running around 35 MPH, and when in no wake areas runs even cooler.
Any advice appreciated
I have a 1988 OMC Cobra Drive, 350 Chevrolet. It Idles fine and the tach reads 800-1000 RPM's.
At 35 MPH at plane it reads 4000 RPMS, but at WOT it Reads 5900 RPM's at 52 MPH. That tells me I should run a 25 pitch prop not the SS 21 I have now. Taking into account each prop pitch increase lowers RPM's by 200, that should put me at 5100 RPM's and more top end. The specs say it should run at 4600-5200 RPM's.
So It seems either I am under proped, or my tach is faulty. I did restore this and replace the tach, but the idle does seem correct. It runs about 140 degrees at 35, but does go to 180 when running wide open and doing some quick turns. It does come back down to the 140 range when running around 35 MPH, and when in no wake areas runs even cooler.
Any advice appreciated
