1980 25 ft cabin cruiser prop?

[smfeight]

I bought a 1980 25' Gran bateau(a great old cabin cruiser), but didn't come with a prop. It has merc260 with hyd trim tabs. I bought a 15 dia x 16 pitch 4 blade alum prop. Could not get it over 3200 rpm and would not plane using the outdrive trim(had to use the hyd ones) and lousy reverse control. I took the prop off my 18' openbow(it is a 14 dia x 19 pitch), got 3700 rpm better planing and more control in reverse but still felt slow. WOT should be 4400-4800. Thanks for the helpand I plan on going out next weekend to enjoy the sun for awhile.

 

[steelespike]

Re: 1980 25 ft cabin cruiser prop?

Your 1100 rpm off. You would have to drop to about a 14" pitch to gain about 1,000 rpm A 14 seems little extreme to me with a 260.If you went with a 15" diameter you would be at 11" pitch.
Is the bottom clean?The motor in excellent tune? Throttle opening all the way.Good compression?Perhaps the boat has absorbed water?

 

[smfeight]

Re: 1980 25 ft cabin cruiser prop?

The boat has been out of the water for a 1 1/2 years. Was in the lake for 7 yrs before that full time. Just got it tuned up and the motor rev to 4400 at WOT out of the water. The bottom needs to be stripped and redone, I plan on doing that this winter, also replacing the throttle cables then. I would like to know which prop I need to get without buying the wrong one. Thanks again.

 

[steelespike]

Re: 1980 25 ft cabin cruiser prop?

hwsiii has a form with Qs for info on your setup.Look for his posts.
You will find it.Otherwise get the bottom clean.Check for wet floatation foam under the floor/deck.Be sure motor is in excellent tune,throttle opening all the way.Be sure all cylinders are firing We have had new boats here missing a cylinder.Reving out of water doesn't mean anything.Make a few test runs
in the spring with your present props.Get us the rpm and speed. We can tell better what you need.
No way otherwise without original info or someone has the same boat can't tell.