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1979 MCM170 coil substitute

jw_in_dixie

Regular Contributor
After running fine at all rpms

After running fine at all rpms for 30-40 mins can't get rpms up past 1400 without it dying. This is after changing skiers and idling for a few mins. Have gone thru fuel system and carb. Now suspect coil. What old car junkyard coil can I try before buying a new one? Tnx.
 
"Hi Warren,

Exactly how did


"Hi Warren,

Exactly how did you go through the fuel system? Empty tank and put in fresh gas? Replace all fuel filters including inline, in-pump, in-carb? Open up and clean carb bowl and jets?

After that you may want to look at points gap, condensor, distributor advance weights. Didn't you go to the pertronix ignitor?

Did you pull the spark plugs to make sure there is no water in the cylinders? That's a commen problem with boats used for skiing when your exhaust flappers give out.

If you still want to replace the coil then go with a marine designated one at least. There is no 'auto' version of this motor."
 
"Hi Mr Sounder. Believe me, I

"Hi Mr Sounder. Believe me, I have done all that, repeatedly. The mystery is that it runs fine for 30 to 40 mins, then after idling 3-5 mins it won't rev up. Will run fine up to 1500 rpm. Try to get more and it dies. A week later it repeats the cycle without my having done anything to the motor except shut it off and go home disgusted. Seems if it was a failure, ie water in the cyls, it wouldn't start and run fine for 30-40 mins. Got to be something failing due to heat. Motor temp stays at 140 deg, BTW. I have had the boat many years and it has never done this. Beats me. Only thing left is the coil, as I see it. I will get a Sierra and try that. Appreciate you advice and counsel. JW"
 
Did you ever dig into the dist

Did you ever dig into the distributor and check the advance weights? Seems like you've had this problem for most of the summer now. I'm sure it will fix itself around the end of september? ;)
 
"Yep, dist wts moving freely.

"Yep, dist wts moving freely. You're right, been working on this problem all Summer. Spent more time on my knees than Father Flannagan. LOL. JW"
 
Warren:

Have you put a timi


Warren:

Have you put a timing light on the engine when it acts up? The advance weights may be jammed.
 
"How about pulling the fuel li

"How about pulling the fuel line off and see if you're getting good pressure when the engine is cranked? Be carefull doing this with a good oil absorbtion diaper, blower turned on, and a fire extinguisher close by. I've had to do this a couple of times on another boat to tell me I wasn't getting enough fuel. The boat would run great for a few minutes and then run the bowls dry until it filled up again. That was a Volvo dual carb set up which was crap anyway. Turned out to be a dried and cracked diaphram in the pump."
 
"Guy, I have not put a timing

"Guy, I have not put a timing light on it while giving the problem. Only go out in daytime and I doubt if I could see the marks then. May have to try it tho. Tnx.

P Sounder, I have a Bendix elec fuel pump pushing gas to the manual pump. Have not tested flow while running but I did check the pressure out of the EFP= 3 PSI, per specs. I let it pump into a two leter bottle held above the float chamber level and it pumped a pint in 15 secs. Also checked the gas flow at the carb with just the EFP running = plenty. New filters everywher Beats me. The way it acts seems more of a fuel problem than ignition. I may use a squirt bottle of gas into the FA next time it balks, plus spray Coolit on the coil. See if either helps. Yes, I have a fresh fire ext onboard. Thanks for your thoughts. JW"
 
You can purchase a external re

You can purchase a external resister coil from any auto store. It would be a coil for a POINT ignition only. Your wiring harness has a ~ 2 ohm resister biult into it.

Have you messed with the wiring to the coil????
 
Warren good to know all the fu

Warren good to know all the fuel delivery has been gone through. The fuel squirt is a good way to tell if it is a fuel problem or not. Let us know.
 
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