25HP Johnson runs full out then cuts off every mile

I read several posts with similar problems. However, I just rebuilt my water pump and it is circulating well, so I would guess that a coil might have a crack in it and once it heats up and expands,the motor is shut off. So how do I determine if a coil is bad in this case?

My motor is very hard to start as well. I have been using starter fluid for a while now, and now that does not always convince it to start up. I also have an issue with it wanting to die out after starting even while pumping the primer bulb. I have recently soaked the carb but have not rebuilt it, however i have cleaned out the float pan. Any thoughts would be greatly appreciated. And thank you for all the help ya'll have given so far, really am grateful. Thanks

Re: 25HP Johnson runs full out then cuts off every mile

Using starter fluid is a quick way to ruin the engine. Use a mix of 2% (50:1) fuel oil if any. If engine does not start on this mix, you most likely have no ignition. However we need to know the model number to determine if this is one of the engines with the dreaded UFI power pack??

Re: 25HP Johnson runs full out then cuts off every mile

Haffiman said:

Using starter fluid is a quick way to ruin the engine. Use a mix of 2% (50:1) fuel oil if any. If engine does not start on this mix, you most likely have no ignition. However we need to know the model number to determine if this is one of the engines with the dreaded UFI power pack??

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J25RERC. I believe is the model. It is a 1994, rope start, long shaft.

Re: 25HP Johnson runs full out then cuts off every mile

The good news, no UFI, but external power pack!!
Start by taking apart all connections and CLEAN. Ground screws (powerpack), rubber plugs, coil leads etc -all!
Test your primer system:
Pump up pressure with primer bulb, open throttle plate fully, pull the primer knob. You should see fuel squirting in behind the throttle plates??
If not, pull hose off carb and check, if OK, check if nipple in carb is blocked.
Get a spark tester and check that you have decent spark on both cylinders??