350 Magnum Misfiring and stalling after a long run at low speed.
 

Hopefully someone will know what is causing this.

This is a mid 90's engine with carb. It starts fine and runs fine at all speeds, all day. At the end of the day we go back thorough the harbour at the 12 knott speed limit for about 20 mins. Then we drop to 6 knotts for the final part and the engine starts coughing and spluttering, backfiring and then dies. It wont re-start unless we leave it for about 15-20 mins, then it starts but runs rough.

I have put a new water/fuel seperator filter on but that made no difference. The engine has been out for a new transom/gimbal assembly but I dont think it should have made a difference.

Any ideas?:confused:

Re: 350 Magnum Misfiring and stalling after a long run at low speed.
 

Just in case anyone has a similar problem, it is now fixed. I replaced the ignition coil and it is now running great. Looking back, this problem has been around for a few years gradually getting worse. The common factor was that the engine would run great at all speeds but after about 45 minutes of use it would cough and splutter and ultimately stop. Leaving it 15 minutes it would restart but run rough. Hope this helps if anyone has a similar problem.

Re: 350 Magnum Misfiring and stalling after a long run at low speed.
 

That is a typical tell tale sign that the coil was sorry must have missed your post earlier the earlier post sounded like might have been bad tank of gas, but once you mentioned it shut down once hot coil for sure.