I got a 1990 200HP looprr, with 70 psi compression evenly on all 6 cylinders. Just asking to see what results have been on other people's decarbing. Has it brought you up 5psi? 10psi?
It all depends on the level of deposits and what is causing a low compression reading.Some use decarb as a measure of control and others for a remedy to a coking issue.If your rings are really coked up bad a good decarb could raise the compression significantly.However when rings get coked up real bad the piston is slopping around and scoring cylinder walls.In short ,decarb is primarily used as a maintenance practice.<br /><br />Insure that your compression guage is calibrated and your test procedure is correct in obtaining the compression numbers.<br />Also insure that a given engine is propped to turn in the upper limits of its manufacturers wide open throttle operating range.This will greatly reduce coking due to a continuously lugged engine.
A simple way to avoid the decard is to run OMC carbon guard as per directions. Carbon is a very stubborn substance, you are not going to get rid of it with a few squirt's out of a squeeze bottle. You must also run the engine in the proper RPM range. In my experience, the only way to free stuck rings. is to take a wrench to the engine.
