'76 merc 85 HP

scottyb68

Recruit
Joined
Sep 11, 2010
Messages
4
Ok, we had a lot of trouble keeping this motor running at low speeds all summer. My dad brought it to a mechanic in the sticks. He said that there was no compression, the motor is shot. I did compression test, if top cylinder is #1 and bottom is #4 then numbers 1 and 2 read 110 #3 read 118 and #4 read 120. Is that low compression for an outboard? If it is, is it possible to resleeve cylinders or bore them to put larger pistons like a car motor? Is this motor shot? Or is it just needing a fuel pump (or what ever outboards use to move fuel.) At low speeds (docking, getting on trailer) the engine would quit or when we tried to get it started it took forever to get going. Once we were running it seemed to run good. Thank you in advance.
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: '76 merc 85 HP

Howdy.

Welcome to iboats. :)

Those compression numbers are fine, Scotty. You may have a small problem with link 'n' synch or carbs. Get yourself a Service Manual (OEM, not aftermarket) and come back for any guidance you might need.
 

chum1

Petty Officer 1st Class
Joined
Apr 15, 2010
Messages
359
Re: '76 merc 85 HP

These are good engines, especially the ones with adi ignition (4 coils) you may want to find a more knowledgeable stick mechanic.
 
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