[ccnoah]

Here's the story:A friend bought a used boat with 82 150hp V-6 Mariner. Boat had sat for approx. 3 years, however the motor had not been run since being last serviced at the shop, so the motor had not sat with used gas in it. Unfortunately, the 3 year old gas was still in the tank, not drained...The motor was started and run in a tank on the old gas (mistake I know!) for about 20 minutes. Sounded OK, a little smokey maybe. Idled OK. Restarted OK.Motor sits unstarted for 2 weeks. Motor now starts hard, not at all and won't idle. Will start with throttle in full forward position, but can't idle.Tried new fuel mixture in a clean fuel tank, verified fuel getting through pump and enricher. Sounds like not all cylinders firing. Compression checked out OK. 5 cylinders @ 120 psi, 1 @ 130 psi. We have fire at all cylinders. I guess take the carbs apart next?Noticed something else. Played with a ground wire to the block that was worn, and the key alarm started working, except it stayed on when the engine cranks for the 5-10 seconds it will run.Couldn't find anything on the alarm in the book. Is the alarm staying on while the engine is running meant to indicate a problem?ThanksChris

[clanton]

I would look at carbs, dont mix main jets some of the merc have different size main jets in the carbs. If it sat for 3 years, I would do waterpump, fuelpump, and pressure relief valve. Alarm , disconnect sensor one at at time, if alarm still stays on with sensor disconnected the alarm module is probley bad.