Merc 3 cyl 2 stroke

[steele m.a.]

I have a strange motor I need assistance with . A mercury 2 stroke , in a
Bayliner 20 ski boat ( sterndrive ).
It is a 3 cylinder vertical 2 stroke .
I need to know more about this beast , if any one out there can assist me.
A friend got it , with boat , as an insurance adjustment .
It runs , but is not as reliable as I would like it to be.
The Merc shop says it's doing what it's supposed to do , but I disagree .
It won't idle , it has dual carbs , synchro joined , on one side of the thing .
Answers ?
marksteele2010@yahoo.ca

[gonzo]

By don't idle, do you mean it dies?

[steele m.a.]

Yes . Rough running beast . Owner has me holding dual throttle open to keep it alive.
Won't idle - dies .

[gonzo]

Start with a compression test. Then test the spark on all cylinders. Rebuild the carburators and synchronize them. Adjust the timing.