compression 135 evinrude

[evinrude55]

I went to buy a late 1970s evinrude 135 today. The motor was very clean and appeared to be taken care of. I first decided to check the compression.

Top left was 150
Bottom left was 125
Top right was 125
Bottom right was 125

The 150-125 raised concern. Although started the motor, idled and revved excellent. everything seemed to be ok. The owner said It had maybe ran 30 minutes in 3 years. After running it for 5-10 minutes we turned it off I checked again.


Top l 145
Bottom l. 120
Top r. 120
Bottom r 105


I probably would have bought it if the bottom right didnt say 105 and had stayed 120. The owner who seemed knowledgeable said if I ran it that everything would even out. Is this true or did I make the right decision not purchasing?
Original price was 1100 when they said compression was 125 on all four. I offered 700 they said nine would be the lowest. After leaving they called and said 800. Thoughts?

 

[boobie]

Re: compression 135 evinrude

To me that's to much variation in the compression but a GOOD decarb might straighten it out. It's your choice.

 

[evinrude55]

Re: compression 135 evinrude

How much could this decarb raise it? I dont think the guy lied when he told me they were all 125. Could this just been random numbers from sitting? The motor ran and idled ok it seemed. What could happen if those numbers are right? Worst case having 145 120 120 105?

 

[racerone]

Re: compression 135 evinrude

Model # of this motor ??---The 135 was last marketed in 1976.

 

[emdsapmgr]

Re: compression 135 evinrude

Those 135's had some of the highest compression heads of the crossflow family of V4 engines. I'd expect minimum of 125+ on all 4 cyls. You've got something unusual going on with the 150# cylinder. Hard to explain unless it's got a non-matching piston-pretty unusual. The problem cyl is the 105 one. That's outside the allowable 10% compression variance allowable between each cylinder-by the factory. I'd be concerned that this may indicate a teardown and overhaul may be in this engine's future. It's always possible that the head gasket seal ring is shot on that head, and that a simple head gasket replace is all that is needed. That would be a best-case scenario. Head gaskets can go if the engine was ever severely overheated. Based on those final compression readings, I'd negotiate any purchase price based on the assumption that a complete rebuild is required. If you even want to get into this much work... Boobie is correct, a decarb may bring the compression up somewhat, but I would not expect it to bring the cyl all the way back up to the others.

 

[Big Fish Billy]

Re: compression 135 evinrude

All good advice, I would just add, a repeated decarb, it is possible that the rings are really stuck, and repeated decarbs along with use will free them up. How much are you paying? If it's worth pulling it apart and putting a couple hundred more into it (doing it yourself), that would be your decision.