1986 22 ft Larson Delta Conic prop specs?

[Scuba 2]

Hello, I just purchased a 1986 22 ft Larson Delta Conic Cabin Cruiser. Does anyone know what prop size this engine calls for?

It has a 3.7 Merc Cruiser, Alpha 1. The engine is strong and only has 60 hours on it after a rebuild, also has a new four-barrel carb. It came with a four-blade prop and I would like to go to a three blade and try and get a few more miles an hour out of the engine.

The problem is I do not have the boat manual and do not know the recommended RPM or WOT, or original prop specs.

I have been told that the four blade is better for quick starts and an earlier plane. But this past Sunday, the engine was at 3200 rpms and I don't think I broke 20 mph.

Any help would be appreciated and thanks.

 

[hooch-7]

Re: 1986 22 ft Larson Delta Conic prop specs?

how did you get a 4bbl carb on your 3.7l merc? what parts did you use and where did you get them? I would like to get alittle bit more out of mine if its possible.

 

[Silvertip]

Re: 1986 22 ft Larson Delta Conic prop specs?

Look on the prop you have now for the diameter and pitch. Its usually on the barrel of the prop or on the hub. You can "measure the diameter". If its a four blade measure across two opposite blade tips. You can't measure pitch but its usually stamped on the prop somewhere. At 3400 rpm either the boat is full of water soaked foam, the engine needs a very good tune up, a very wrong prop is installed, or attempts have been made to modify the engine which rarely works and only makes things worse. Do some investigating before blowing money on props to solve another unrelated issue. Just so you know, prop selection is a crap-shoot as there is no such thing as a "standard" prop for any boat/motor combination.