Rpm/Prop question

[metal249]

I just bought a 1986 seaswirl with the 3.0L Omc. The manual says the full throttle operating range for the motor should be 4200-4600rpm. At the lake, I could only get 3400rpms out of it, empty, at full throttle. The motor was just tuned , oil changed, and its only 2yrs old. The prop is a little chipped and says 13 1/2" X 17. I think I need a different prop, but I do not know what to get. The sizes I keep seeing for my boat are 13 1/2" X17-13 1/2 X19. It also lists 13 1/2 X25-13 1/2-27" for bass boats. Any help is appreciated.

 

[Silvertip]

Re: Rpm/Prop question

There is something drastically wrong with this boat and changing props is not the answer (at least not one of the first things to change). Either a very bad tune up was done, the engine is worn out or not making full power, the throttle is not opening fully, the boat is full of water soaked foam and therefore extremely overweight, the hull is dirty, the outdrive has the wrong gear ratio, the tach is wrong, and the list goes on. 3000 RPM with a 17P prop simply does not compute at that prop is about right for that engnie. Lots of things to consider before spending money on props.