Mercruiser 165 Engine Anomaly

I have a 1986 Four Winns 21&#3

I have a 1986 Four Winns 21' boat with a Merc 165. I recently had the voltage regulator changed and had electronic ingntion installed. Since that time after about 30 minutes of running at a slow speed around 850-1300 rpms the engine starts to act like it wants to stall for a brief moment and then it idles at normal. This cycle is about 15-20 seconds and it continues to repeat. I then took it up on plane at about 3000 rpms and then the engine went from 3000rpms to 2400 rpms and continues to float back and forth. Does anyone have an idea what could be causing the problem. The mechanic at my marina is stumped.

Have you tried new fuel filter

Have you tried new fuel filters?

"Rick...

It sounds electric

"Rick...

It sounds electrical to me. Was the electronic ignition new or used? If used, there is a chance that the coil is going bad and breaks down after heating up. Or something else breaking down after getting hot. Is there a possibility of putting the old ignition back in and seeing if the problem goes away? That would narrow it down some.

Wrench"

"which electronic ignition did

"which electronic ignition did you get? Some types require you to bypass the resistor wire and supply 12V to the coil, other systems you leave the resistor in but only if using the stock coil..
165?? is it the inline 6 cyl? or the 224 cu in. Fordcruiser 4?"

"Guys, Thanks much for the qui

"Guys, Thanks much for the quick reply. I am going to talk to my mechanic today and ask these questions. The engine is the Ford four cylinder."

No it is not a ford 4 cyl.

No it is not a ford 4 cyl.

This is a mercury motor.
It is a special 4 cyclinder with a ford 428 V8 Head on it and the ingition is a AC delco point distributor. If it has been converted to electronic than that is fine. I have done many myself.
Pull the point base plate out and make sure the advance wieghts are moving freely and there is no missing springs.

Also this is a "closed cooling system and you have a RADIATOR cap Correct? Look very closley to seee if you have any antifreeze/ water trails running down into the spark plugs. This will short out the plugs and act like a timing issue.

Start there

"Guys here's the latest.

"Guys here's the latest. My mechanic found that the sparkplug wires now 22 years old were shorting out and the coil was getting hot. He changed both and for now all seems well. He will test it again tomorrow and hopefully it will be reliable once agaain. If I continue to have issues I will post again. I really appreciate all the help and quick feedback from you all "