1996 Evinrude 150 Ocean Pro - What size prop for a 1974 Mako 20?

BarnegatMako

Recruit
Joined
Dec 8, 2017
Messages
1
Good morning fellow boaters! Hoping someone can point me in the right direction. I have a 1974 Mako 20 with a 1996 150 Evinrude Ocean Pro. I just purchased the boat this summer and only had it out about 5 times. Can't get past 4200 rpms - 31/32 mph.

I was told this is a prop issue.

Engine has a 14 1/2 x 19 aluminum prop. I want to get a stainless prop and looking for recommendations.

Any help would be appreciated.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Was combo lightly, medium or fully loaded when only achieved 4200 wot rpm? What's the max wot rpm range factory stated for that engine ? surely over propped for current load running a 19 pitch prop..

Happy Boating
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
Your rpms sound a bit low, even with a 19 pitch. Make sure the carbs are open fully when when the throttle is at max. What condition is the engine in? Compression numbers?
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
With a 15 pitch would assume that engine will rev towards middle wot rpm range if 4500-5500 wot revs is its wot range. If already achieved 4200 rpm with a 19 pitch going 4 less in pitch should theoretically dial + 800 wot revs towards 5000 range which is a wild guess..

Could have a waterlogged boat, prop is entering hub slip territory, engine is with tech issues, badly height seated or trimmed, tach is shot or a cocktail of all 5 issues.

Happy Boating
 
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