[firemarshalart]

I am looking at a boat that has a 1996 200 HP Mariner. The owner says it has low hours (I've never seen an hour meter on an outboard) has no idea of the engine compression though he says it runs great. I have a compression tester although I'm somewhat of a novice. Can anyone tell me if there is a special method of checking compression on this motor other than removing spark plugs, installing the compression gauge and turning the motor over? Also what should the compression be? Finally, is there anything else I should be looking for? Thanks

[JB]

Look for all 6 cylinders to compress within 10% of each other. Variations in guages, conditions and technique prevent any useful specs on psi.

Just remember that the likelihood that 6 cylinders would go bad by the same amount at the same time is remote.

[gss036]

firemarshalart , normally you would look for somewhere around 110-120 lbs and as JB said, within 10% of each other. Main thing is even numbers across all 6.

[hkeiner]

Finally, is there anything else I should be looking for?

In addition to checking compression, it is a good idea to check for a strong spark on all cylinders (using a spark tester) and checking for a leak in the lower unit oil seals (by draining a bit out and looking for a water or milky looking oil coming out). There a other things that can be checked but these three would be the minimum in my opinion.