Will e-mailed me asking about the compression test. I thought I would post my response since I am hardly an expert on this stuff - I basically learned it here!
I wrote:
Definitely post this Q on the site, you will get plenty of advice. Also, if you have time, do a search on the site (at the top of the forum section) for compression test. Lots will come up.
First you find out what the PSI for the engine cylinders is supposed to be. Say its 130 psi. Typically, all the cylinder heads should be within 5% of each other - though I seem to recall that it's different with Yamahas in some cases. You then insert a compression gauge into the cylinder head where the spark plug goes and take a reading as the cylinder moves - therefore creating pressure in the cylinder. If compression is off in a cylinder could be a cracked block or a leaking gasket, etc. It's a sure sign the engine needs work.
You MUST have a compression test done. Since Ocean Beach Marina is a dealer, I am sure the mechanic at the dealer will perform it with you there, and charge you of course. Ask him what it should be and watch him do it. If you can't be there, make sure he gives you the numbers. Sometimes people say the engine "has compression". But that is meaningless. What's important is that it is what it should be, based on the manufacturers specification. Hope this helps, I am not a mechanic by any stretch of the imagination, but this is something everyone on the Wellcraftv20 site swears by. Last thing you want is a lemon.
Hope this e-mail doesn't find you too late. I'll post on the site too - someone may have the compression numbers for an 89 Yamaha 135 or have something to add to this or correct me if I am wrong.
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