stingray220sx

The 350 MAG MPI (300hp) Mercruiser in my 2001 Stingray 220sx has had repeated ignition failures, leaving me with $700.00 in tow bills, a major headache, and a "See, I told you not to buy a boat" wife. Basically, the engine will run for 20 minutes to several hours and then Kaput! No warning. . . nada. I have replaced the cap, the distributor sensor (twice), and the coil. Since the last breakdown this weekend, I have noticed that the negative terminal of the coil is visibly sparking when the engine is cranked (it may have been doing this all along, but I did not notice). Is suspect that the coil is now toast, but I don't think that the underlying problem was a defective coil. I suspect that I could replace the coil 20 times and it would keep frying. What would cause a coil to burn out in an hour or two? Any input would be great! Thanks.

tssteph

Unhook your tach and run it. Every repeatable ignition module blow that I have heard of was traced back to a faulty tach. Unhook it and run for a while and see.

JUSTONCE

each time you breakdown does it restart when it cools off or are you replacing modules each time. If its frying ign modules than I think tssteph has the right idea. If nothing else its a good place to start. I've never had a tach blow a module but I've heard of it happening and I have had bad tachs reak havock on my timing and ign sys.
Martin.

baja bailey

My father in-law has a 1999 350 mag mpi. He was towed 3 times within about a 3 week period last summer and each time the ignition module had went out. On the third time the merc mechanic told him they had a problen on this engine with the module and it was supposedly replaced with one that was gonna be okay...He ran the rest of the summer with no problems...

jafo

I had an ignition failure last year on one of my 350Mags- it turned out to be the wire going to the negative terminal of the coil. It was broken inside the ring terminal where it was over-crimped. Not the easiest thing to find- I was actually thinking of swapping coils engine-to-engine when I found it. It was fatigued enough to fall into the bilge when I removed it from the coil.

Beware of the wiring harnesses on the Mercs- unlike the jet aircraft I work on where electrical connectors are crimped on with calibrated tooling, the wiring harnesses on the Merc engines seem to be overcrimped, which leads to wire breakage. Harder is better, right? Not in wiring.
This is the third failure I have seen of this type- all have been at crimped terminals; one at an oil pressure transmitter, and another at a water temp sender. Might be worth checking.

Replace ONLY with sealed-end terminals and heat shrink! Double crimp, but do not smash the wire inside the terminal.
Jim

Mbam

Do you mean it is sparking from the center tower to the neg term? Also, do you have an Alpha drive?