4.3L will not run after warming up

[martys]

I have a 1992, 4.3L, V6, Mercruiser; the engine (cold) starts fine, runs great for about 15 minutes (at all speed ranges). When I slow the boat down to idle speed, within 5 to 10 minutes, the engine knocks (like firing only on 4 cylinders) then dies. It will not start again until I wait about 1 hour.<br /><br />While waiting for a tow, I took out a spark plug and checked for spark, which there was not.<br /><br />The dist. cap, and rotor are last years but look ok. I installed plugs this year. The boat has been operating great until now.<br /><br />I tried a new coil, but the same thing happen.<br /><br />Should I start with the dist. cap and rotor or am I missing something in my service manual.<br /><br />I just like to get some opinions.

 

[Chris1956]

Re: 4.3L will not run after warming up

Marty, If you do not have spark at the plugs, put a spark plug onto the coil output wire. If no spark there, your ignition amplifier, ignition sensor or coil are bad. I was able to troubleshoot my Mercruiser T-bolt IV using the manual.<br /><br />If you have spark at the coil, maybe cap and rotor are bad. BTW, heat can cause ignition amplifier or sensor to fail. Coils tend not to "get better" when they cool off.

 

[rbezdon]

Re: 4.3L will not run after warming up

also, wires can be a problem, even if they look good they still can be bad.

 

[martys]

Re: 4.3L will not run after warming up

After coming back from a two week vacation, I started to trouble shoot again. I found the problem in the ignition sensor and replaced it. The plus side of this, I found that my coil had a crack on the bottom and two spark plug wires had cuts in them which were easy fixes. The whole job cost me under $100.<br /><br />Thanks for your help,<br /><br />Martys