I'm looking at an older motor. Is good compression THE MOST important thing?

[DJ_Allatoona]

My current motor is dead. An older motor I'm considering has (reportedly) 140 compression on all cylinders. I have no powerhead experience at all...but I feel comfortable with everything fuel, electric and lower unit related.

So if the compression is good, and other stuff is fixable, what else would you guys be looking at if you were going to see this motor in person?

 

[QBhoy]

Corrosion and quite importantly the trim pump. These can be as much as the cost of an old engine if you buy new.

 

[Scott Danforth]

paperwork proving ownership is probably the most important thing

I would check compression yourself. I do not know of an outboard with that high of compression personally.

compression
visual check of all wiring and hoses
comparison of serial number on the tag and the core plug
paperwork

 

[Chris1956]

If you do all your own work, compression is the most expensive thing to repair ($1K+) Next is replacement of the whole PTT system($1K). Next is ignition components, followed by trim pump motor(hundreds$). Lastly and usually considered maintenance is water pumps, carb rebuild kits, fuel pump kits etc(Tens $).

So if the motor has good compression and a good PTT system,you are most of the way there dollar-wise.

 

[jimmbo]

Good compression is One the things that are important. An engine with a hole in the crankcase can still have Great Compression but...

 

[thatone123]

Some states have no paperwork on outboards. Compression basically is the most important thing as that would be the hardest and most expensive thing to fix and many outboard rebuilds don't seem to last. Properly breaking them in which is a time consuming and exact procedure is one reason. You can replace all the periphery components albeit some might be expensive but all are cheaper than a new motor unless you might find a good used one, many times with other problems.

 

[flyingscott]

So what motor are you considering? If it is from the 70s the wiring will be a toss up whether it is good or not.

 

[The Force power]

I addition of all the good advice given in the previous posts; check for availability of the parts (potentially) needed for that particular motor of choice

 

[Texasmark]

My mid range Mercury Service Manuals state that anything less than 120 PSIG can be a problem. At 140 you are in great shape on that metric. I just bought an engine with 129, 129, 129, 130, just out of a competent marine dealer's shop and it is a stout performer. I never saw a mfgr. post compression (and the way they tested for it) on new or newly broken engines. Don't have any idea as to what that number is.....betcha Faztbullet knows!

 

[Faztbullet]

Depends on how old it is..if its a distributer type walk away IMO.