Engine too small (options?)

N

nightstalker

Chief Petty Officer
Joined
Dec 10, 2003
Messages
570
Here's the problem. My buddy has a 19.5' Aquasport CC (1985). He had a 90 Merc. on it that blew. She ran at 30 MPH with the 90 and tacked out at about 5200. He was tight for dough, so he bough a rebuilt 75 HP Merc. The 75 is too small. She just about gets on plane and runs at about 22 MPH. I think that trim tabs would help, but they are too expensive. I was thinking about those "wings" that attach to the engine skeg. Do you think they would help him to get on plane and increase the speed?<br />Stalker
 
LubeDude

LubeDude

Admiral
Joined
Oct 8, 2003
Messages
6,945
Re: Engine too small (options?)

My personal belief is that the foil will help his problem of planing, but may actually hurt his top speed. Maybe not.
 
B

BF

Lieutenant
Joined
Apr 8, 2003
Messages
1,489
Re: Engine too small (options?)

What WOT rpm is he making on the 75? I bet it's overpropped. He should make sure he's propped right to get the most out of it.... lugging the motor all the time isn't good for it.... maybe even the 90 was overpropped. I don't know that motor, but 5200 sounds a bit low.
 
S

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: Engine too small (options?)

I would not spend much in looking for a solution as no matter what you do the 75 hp won't cut it. Save your $ for more HP - minimum of a 115.
 
N

nightstalker

Chief Petty Officer
Joined
Dec 10, 2003
Messages
570
Re: Engine too small (options?)

Originally posted by SoLittle:<br /> I would not spend much in looking for a solution as no matter what you do the 75 hp won't cut it. Save your $ for more HP - minimum of a 115.
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The 75 seems to be tacking out at about 4800 that's why I figured it was working too hard and would benefit if the boat was better planed out.<br />Stalker
 
S

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: Engine too small (options?)

You may be able to pick both rpms & performance by raising the engine a bit. Where is the cavitation plate relative to the bottom of the hull?
 
D

DJ

Guest
Re: Engine too small (options?)

You'll kill that engine in short order at 4800 RPM-WOT.<br /><br />Get the right prop for it. 5500 RPM-minimum.
 
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