Mercruiser 140, Alpha MR - can't locate electrical miss

[boozer1966]

I'm at my wit's end. Boat runs great for about an hour, then develops a slight electrical miss which turns into a major misfire causing the engine to shut down. Will re-fire and idle fine but will not accelerate. After another half hour or so, it will begin running normally. I am confident it is electrical and not fuel. I have checked all ground connections. Has Pertronix electronic ignition. Distributor? Any ideas appreciated.

 

[achris]

Re: Mercruiser 140, Alpha MR - can't locate electrical miss

When the Pertronix was put in, was the resistor wire removed or bypassed?

Chris.....

 

[boozer1966]

Re: Mercruiser 140, Alpha MR - can't locate electrical miss

Removed.

 

[Fastatv]

Re: Mercruiser 140, Alpha MR - can't locate electrical miss

I'm at my wit's end. Boat runs great for about an hour, then develops a slight electrical miss which turns into a major misfire causing the engine to shut down. Will re-fire and idle fine but will not accelerate. After another half hour or so, it will begin running normally. I am confident it is electrical and not fuel. I have checked all ground connections. Has Pertronix electronic ignition. Distributor? Any ideas appreciated.

Very curious as to what you find. My 1989 3.0 with DDI seems to be doing something very similar. In my case, I'm thinking its the plug wires. Or actually, one wire that's getting hot, and no longer conducting.

 

[boozer1966]

Re: Mercruiser 140, Alpha MR - can't locate electrical miss

I have new plug wires, cap and rotor. It acts like the timing gets out of whack. Occasional backfire thru carb. Then it will run well, then not. Advance mechanism in distributor is visually intact, oiled and moves freely. I'm not sure what else to check.

 

[achris]

Re: Mercruiser 140, Alpha MR - can't locate electrical miss

Is the distributor grounded properly?

 

[boozer1966]

Re: Mercruiser 140, Alpha MR - can't locate electrical miss

How is the distributor grounded?

 

[boozer1966]

Re: Mercruiser 140, Alpha MR - can't locate electrical miss

I think I have traced the problem to a series of faulty connections and circuit breakers on the dash panel, one of which powers the ignition switch. None of the breakers seem to function properly. I will replace them and button up the wiring. The breaker for the ignition switch seems to be where the short was coming from. Electrical problems can be a real pain in the ***.

 

[harleyman1975]

Re: Mercruiser 140, Alpha MR - can't locate electrical miss

Was just gonna suggest you check voltage to coil when problem occurs.