How low is too low compression 95 Johnson 90 hp

J

Jim in ADK

Recruit
Joined
Jul 19, 2011
Messages
4
140,140,140,90 The boat starts and runs smooth. It lacks power to plane the boat.
4000 rpm max 10 mph on a 17 ft vee turning a 14x17 prop.
 
nwcove

nwcove

Admiral
Joined
May 16, 2011
Messages
6,293
Re: How low is too low compression 95 Johnson 90 hp

the 140's are great, the 90 is well out of the +/- 10% that is acceptable. maybe im readin wrong.....but are you saying that the motor is spinning up to 4000rpm, but the boat only goes 10mph? if so, sounds like your prop spun its hub.
 
B

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: How low is too low compression 95 Johnson 90 hp

The cyl with 90 lbs has a prob. Pull the head and look at the cyl.
 
E

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: How low is too low compression 95 Johnson 90 hp

OMC made two types of 90 hp engines in 1995. The 90 degree crossflow and the 60 degree looper. Which do you have? Unlikely the crossflow compression is actually 140 lbs.
 
J

Jim in ADK

Recruit
Joined
Jul 19, 2011
Messages
4
Re: How low is too low compression 95 Johnson 90 hp

i replaced the prop with a new one and the same result
 
J

Jim in ADK

Recruit
Joined
Jul 19, 2011
Messages
4
Re: How low is too low compression 95 Johnson 90 hp

how can i tell what type looper or crossflow?
 
E

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: How low is too low compression 95 Johnson 90 hp

Post the model number off the engine serial plate.
 
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