It just doesn't run right-200 Merc

[reelapeelin]

Never had a Merc, but did have a 40 hp Mariner elec. start ... never had a single problem of any kind from that motor... 8) ...

[bcmarinamanager]

i love my 200hp Merc. It's a '92 and I had a very similar problem running over 4000 rpm. My prob was the fuelpump though. sounded like it was doing the exact same thing yours was. Mine also runs kinda rough at the lower rpm range, not so much at trolling speed, but mid range, it sounds like it want s to run on out, and then cut back. can't find anyhting wrong with though. i just run with it. By the way, you definitely need to ditch the oil injection. Much Much safer.

I would make sure that the throttle plates are sycronized, alot of the time when people redo the carbs they will not adjust the throttle plate, this causes some cylinders to get more throttle advance than tha others, the engine will troll rough, cough spit and die at idle. take the front cover off of the carbs, loosen the throttle plate screws, then flick each throttle plate and make sure it is shutting all the way, once you get them all the way shut tighten the throttle plate screws and recheck that all of them are are shut all the way down at idle.
Basically if the plates are set wrong the top two cylinders can be trying to idle at a different speed than the midlle two and so on, they have to be all exacty the same for the motor to run right. After you get them adjusted open the throttle all the way up and make sure they are all in the same position at WOT. This is one of the most overlooked steps in two stroke carb overhaul, I bet 60-75% of the motors on the water today are wrong.

Thanks guys for the tips. I'll check the carbs but I had felt the mechanic would have checked/adjusted the sync when he rebuilt them. As to the oil inj, it had been disconnected before I bought the motor. I've changed several sets of plugs, and tried different brands (NGK, Autolite, Champion). I've also bought two more switchboxes and tried those.

My plan is to check the fire at the problem speed, under power with these "spark testers" I bouht at H Freight. These are visual indicators of the charge to the plug. I've already tried these at idle with the muffs on and all cylinders looked the same. I guess most of you know that under load things can look different. Hopefully I can narrow down the problem to one or two particular cylinders. I really think it's electrical. It idles OK (as smooth as a typical 2 stroke :-)) and it now seems to run fine at mid and top end but I'm thinking it could also be one carb or one pair of carbs or one of the reeds. Maybe?