Re: 1975 70 johnson why it dies when exhaust is under water
Fireplug.... The engine may seem like it's running fine, but it is not. Regardless of the problem, always check the compression first, should be approx 100+ psi and even on all cylinders. Let us know what the readings are.<br /><br />Second, with the s/plugs out, check the spark with some kind of spark tester. The spark should jump a 7/16" gap on that model with a strong blue lightning like flame, also on all cylinders. Does it?<br /><br />If the above items check out okay, I would assume that a carburetion problem (fouled/clogged) exists that is causing the engine to run lean.
