93 Evinrude 155 commercial question

JOFO17

Petty Officer 2nd Class
Joined
Apr 23, 2002
Messages
158
I was reading that the commercial 155 was a low compression motor that runs on less then perfect fuel. Does this low compression translate to lower readings on a compression test? Is 75-80 all around satisfactory, or is this a tired old motor?
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Not sure just what year you actually have. Don't see a 155 listed for 1993. Maybe you could post the model number... These engines do have some unusual attributes. Usually these will run on lower octane fuel that is more common overseas. It's possible it will run on 85 octane. In order to do this, the factory could either retard timing or even reduce compression. Not sure which technique your engine uses. Guess it all depends on how it runs. The biggest problem with these engines is the lower unit. It has a lower gear ratio than the normal consumer models, maybe even a larger gearcase. As such, the normal props just don't work well. You will find you'll have to run some very odd pitch props in order to maintain proper WOT rpm's. Then these props will generally not be as efficient through the water when compared to normal consumer models.
 

JOFO17

Petty Officer 2nd Class
Joined
Apr 23, 2002
Messages
158
I don't have a model number yet. It is a motor I was considering buying. The low compression would normally send me running, but I wasn't sure what was "normal" for this motor. It sounds like this motor may have a thirst for gas???
 
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