90hp merc compresion

[Fibertron]

Im looking at buying a 93 90hp merc or a 93 100hp merc. Could you please tell me what the compression should be on these motors. Thanks.

[Carsen]

yo brian, boat is running :D

i made a scale model of it! gonna paint it soon!

got a black max electric mini outboard off ebay for it and picked up some r/c stuff!

i'll get a vid of my boat this weekend...!

-carsen

[Fibertron]

I say the pics, looking good. I started to make a model, just for the wall though, but Inever finished, mabey one day.

[Winger Ed.]

Most shop books say test all cyl. by spinning them at least 4 times for each reading.

If there is more than about 15psi. or some say 10% difference between the highest and lowest, you got a problem.

Another way is feel it run. If it doesn't vibrate too much, they should be pretty even.

If it starts right up without a lot of 'windup', and stops quickly rather than sort of coasting down due to the flywheel effect, the compression is probably pretty good.


A good healthy engine will normally start so fast you almost can't bump the starter and let go of it without it starting and running. And a healthy one will stop revolving the instant you turn off the key.



If that checks out, you just have to make a value judgment from its overall apperance.

Lots of wear on moving parts & linkages and little evidence of new gaskets, wrench marks tearing off the factory paint, plenty of crud indicates a motor that's been run, but not worked on.

Wrench marks everywhere, new gaskets, etc. says its been torn down and overhauled, or at least worked on a bunch.


With that in mind, arrive at what you think its worth compared to a new(er) and fresher one.