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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4724
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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I have a 1985 60hp Mercury, 3 cyl, 2 carbs, low RMP runs

Customer Question

I have a 1985 60hp Mercury, 3 cyl , 2 carbs, low RMP runs great, poor the gas to it and it runs great, then about 5 min later, stalls out. Starts right back up, but at 1/2 to 2/3 throttle bogs out again, runs great till then and at 1/2.
Shut it down and let it rest and ran great full throttle ??
Submitted: 10 months ago.
Category: Boat
Customer: replied 10 months ago.
The motor did sit for over a year without being ran, but the guy seemed to take care to pickle it?
Expert:  Jeff G. replied 10 months ago.

Get a inductive timing light. Run the engine and when it bogs put the timing light on the top cylinder, look for the flashes then repeat on the other cylinders. We are looking for a bad cylinder. If you find one not firing, then trade it with another cylinder. If the non firing moves with the coil then the ignition coil is overheating and needs replacing. If it stays on that cylinder then the problem is in the switchbox or trigger. Let me know what you get. We'll go from there.

Customer: replied 10 months ago.
Jeff I did review your response but have not ran the boat yet, plan was for today Saturday, I needed help doing the timing light, which I do have to see if the cylinders drop off electrically.
I took the fuel filter off made sure it was clean. I was going to take the fuel line off and see how the fuel pump works, but at low RPM's it runs great, so didn't think that would help. Wish I knew RPM data.
Expert:  Jeff G. replied 10 months ago.

When it bogs down immediately after you can start it but only runs 1/2 throttle correct? If so, that is the time to check the firing with a timing light, you should be able to do that in neutral.

Customer: replied 10 months ago.
I used a timing light and at full throttle it was a couple marks above 23. At idle it was in the middle of the scale (I couldn't read#) all 3 plugs have spark. Put in the lake, started perfect idles great, moved away from the dock and put timing light on #1 wire, it ran for ( even shorter time this time) great at full throttle, less than 5 min, then started to bog down. Throttle back to 1/2 and it runs like a sewing machine, move throttle ahead and bogs, from 1/2 to idle it runs great. Didn't see a lot of gas going thru carb, and could see it atomize at full throttle a little as I took the front cover off to see them operate.
I cleaned fuel filter, checked all hoses, all linkage seems to be in order, both carbs open the same.
I work on old cars and have good mechanical skills so not lame there.
Expert:  Jeff G. replied 10 months ago.

From what you describe the stator is bad. Your stator has a high speed and a low speed side. It would appear the high speed side is not working. As the rpm goes up on the low speed the voltage goes down until it can't keep the engine running, rpm drops and it starts running right again. If you have a peak reading voltmeter you can check this by putting your meter on the red lead from the stator, you should have about 180+ volts.

Customer: replied 10 months ago.
Thank you, ***** ***** silly question as I am sure I need to have it running and in the WOT position or where it starts to bog down. Which means I will have to take it back to the lake. No problem.
I got to looking around and found the 2 yellow wires coming from the stator, ( per my Seloc Repair Manual) had the insulation rotted away and were more than likely making contact inside the protective tube cover. I heat shrunk tube around them and cleaned connections. In that manual the show how to test a stator except they say OHM values between Blue & Blue/White stator leads and then Red & Red/White leads. Only problem is I don't have the blue/white or red/white wires, so that didn't help. Seems if the stator is bad I will need special tools to pull flywheel.
I plan on going to the lake today or tomarrow
Expert:  Jeff G. replied 10 months ago.

With the wires being bad I would recommend replacing the stator anyway. Some of the same wire is inside the stator. The yellow wires carry AC voltage to the rectifier for the alternator, charging system. Yes you do need a special tool to remove the flywheel but it isn't expensive. DO NOT remove the small bolts on the top of the flywheel. I'd bet 99% the high speed side of the stator is bad.

Expert:  Jeff G. replied 10 months ago.

Ant news?

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