1985 200 mercury surging.

[Dynobo]

Hello all. I have a 200 merc. that seems to have a surging problem after and while accelerating. From idle it will jump to approx. 3000 rpm and hesitate until eventually reaching 5000-5200. However, when cold it will usually accelerate very smoothly. These symptoms typically don't begin until the engine has been run for a few minutes. The rect. recently shorted and wiped out both switch boxes and the yellow charging wires from the stator. All have been replaced and seem to be working fine. I am presently rebuilding the carbs and will be using a different remote fuel tank to try and alleviate that as a problem. Any suggestions from you Mercury guru's before I haul this baby back to the lake for another go. Thanks.........Bobo

[kjpfish]

if rebuilding the carbs do not fix your problem i would look into this: it should have one of these three items-idle stabilizer, high speed spark advance module or low/high speed spark advance module. i have a 1981 merc 200hp and mine had a idle stabilizer, when it went bad the engine would not go over 2200 rpm. if you have a shop manual it will tell about these and how to test them. they are supposed to advance the timing by 6 degrees.

[Dynobo]

Thanks. If the advance modules did prove to be faulty, could you temporarily disconnect them to confirm or would the engine not run w/ them disconnected??

[kjpfish]

yes you can, if you disconnect it and it runs the same i would assume that is the problem. if it runs worse then assume thats not the problem. i removed mine and left it off the onle effect it has is i have too move the throttle foward some to raise the idle when starting it cold, after that it runs perfect. the way you're supposed to test it is with a timing light. it is an electronic box with three or four wires depending on which unit you have and is mounted over the oil tank.

[jmbkdrmn]

if rebuilding the carbs do not fix your problem i would look into this: it should have one of these three items-idle stabilizer, high speed spark advance module or low/high speed spark advance module. i have a 1981 merc 200hp and mine had a idle stabilizer, when it went bad the engine would not go over 2200 rpm. if you have a shop manual it will tell about these and how to test them. they are supposed to advance the timing by 6 degrees.

when your advance mod went out where did you find one an having no luck there now unavailable. 1981 black max 200.