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86 Mercury 150 takes 5 to 8 minutes to warm-up

L

Loncin

New member
​My motor will not turn more than 3000 RPM with full throttle applied ( in or out of gear) for the first 5 to 8 minutes of operation. Once warm, it runs like a top for the rest of the day. In one instance, I loped out into the vacant, windy lake waiting for warm up where it then stranded me and 5 women (No, not planned or wanted). It ran ok the next day. Thermostats? Electric?

Thanks for any help.

Lonnie
Lamoine, Maine
 
Sounds like it is running on 3 of 6 cylinders.-----Check for strong spark on all 6.-----Could be as simple as a loose wire.
 
Yes, have a look at the wiring.

If you don't see anything out of order you can try simple test at home if you have a flushing device.

I normally use this technique to detect a cracked bobbin on the stator or trigger that goes bad when warm/hot but you may have an issue that it will work on.

Take a hair dryer (borrowed from one of your 5 boatmates :)) or a heat gun and heat the flywheel/upper block until it's fairly warm to the touch. Then start the motor. You shouldn't run it above idle on a flusher but a quick pop on the throttle to see if she will get to max rpms won't really hurt.

If the trick works that would indicate that you have a bad bobbin, probably in the stator (and probably one of the high speed bobbins), that is gaining continuity once it heats up (and the copper expands completing the circuit).

Running only on the low speed bobbins would tend to explain why it would not get above 3000'ish rpms - they simply can't keep up with the power requirement to go any faster until the high speed side kicks in to help out...
 
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