Re: wot rpm not reached
Don't begin to throw parts in random order. Better to act methodically. A 2-stroke engine need 1) compression 2) spark and 3) fuel so:
- do a compression test on each cylinder (around 100psi is OK, even is more important), compression gauge is available for around $25 at auto parts store, if it test ok, then
- check spark on each cylinder (you'll want a 7/16" crisp blue spark), again, a spark tester can be bought for less than $10
- if compression is good and electrical system work then, only, proceed to diagnose the fuel system, which can be a bit more work. A good practice is to first connect the engine to a portable tank with a known good hose/primer bulb assembly to first rule out that part as a possible cause (junk in tank, bad primer bulb, deteriorating hose). If it still do the same, next are the carbs and fuel pump.
If you can't go past 3500 rpm, it could be any of these three previous causes, in cost descending order:
1) hole in a piston, not worth fixing it, unless you do it yourself
2) one cylinder not firing (bad switchbox, or coil), costly but not that bad as 1)
3) clogged jet, or punctured fuel pump diaphragm, easy fix and cheap
In any case, an OEM service manual pay for itself.
(for jestor68: I'm pretty sure the Merc triple from the 90's use surface gap plugs)
Oh, you said you just got the boat: is it from a dealer? If so, please go see them and, if you bought it from a particular, did it ran like this when you tested it or it just start recently?
And, for the mods, I think it should now be moved to the Merc forum...
