Need prop selection help..novice here

[Scuba 2]

Hello, I just purchased a 1986 22 ft Larson Delta Conic Cabin Cruiser. 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.

 

[javelinx1]

Re: Need prop selection help..novice here

boat is too heavy for a 3 blade. maybe a little underpowered.
I would recommend a Mercury High Five with a 17 pitch to get those revs up on that v-6. you need to turn it 4400-4800 rpm to make that boat move.

www.propellersonline.com

 

[Scuba 2]

Re: Need prop selection help..novice here

Thanks for replying!


Actually it is a 4 cylinder, 190 hp at the prop, not a V6. I guess even more under powered than you or I thought.

I did not realize at the time of purchase that it was underpowered.

I plan on being in the water this week, and will see just how much of a WOT I can get.

 

[Bry21317]

Re: Need prop selection help..novice here

If you are only getting up to 3200 Rpms, you might want to check the Spark Plugs, Distributor cap and the normal Tune Up items. Make sure that engine is running correctly.

I would say that is quite underpowered also, not sure, but thats my guess.

I just got a new boat and its a 94 Crownline, heavy boat 2900lbs, 19 foot bow rider and it has a Mercury V8 5.0liter engine in it. It will move now, but its got the power to push it.

And you are 3 feet longer than me, and you are a cabin cruiser also, so you should have more weight than mine does.

How did the owner say that boat performed before with the same prop?

Bryan