stator or switch box?

[twopunches]

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i have a 1992 mercury 115.this is my problem.when my motor runs between 4 and 5000 rpms for a few minutes it looses all power and shuts down.sometimes it starts right back up and when it doesn't i have to wait for it to cool down before it will.also the alarm goes off.Ive had the water pump changed,new thermostat, new plugs,and wires.when out on the water Ive taken the cowling off and felt the motor.its not running hot.it runs fine until you run it between 4-5000 rpms. for a few minutes. it doesn't show up on a diagnostics either.ive also converted it over to premix.im sure i dont have any fuel issues.
any ideas? thank you in advance

 

[Barnacle_Bill]

Re: stator or switch box?

Rebuild the fuel pump. Be sure to get the kit from Merc as they contain new style check valves. According to a Merc TSB ethanol and other fuel additives cause the edges of the check valves to curl up and not seal properly. I had the very same problem with a 75hp Merc and the kit was the fix.

 

[j_martin]

Re: stator or switch box?

Rebuild the fuel pump. Be sure to get the kit from Merc as they contain new style check valves. According to a Merc TSB ethanol and other fuel additives cause the edges of the check valves to curl up and not seal properly. I had the very same problem with a 75hp Merc and the kit was the fix.

Yep, the plastic discs are a permanent fix.

So is burning only non-oxygenated (sic) fuel.

BTW, that alcohol contamination in the fuel tends to take out the inner tube in older Mercury fuel lines, internal and supply.

John

 

[emckelvy]

Re: stator or switch box?

I recently worked on a 115-4 with fuel starvation issues and it did have the 'crumpled up' fuel pump check valves so it's definitely a good idea to go thru the fuel pump.

You could also be experiencing a heat-related stator failure. A good way to diagnose this would be to take resistance checks of the stator low-speed and hi-speed charge windings when the motor is Stone Cold, then take them again after you've run it and experienced the failure.

http://www.boatpartstore.com/mercreadings.asp

http://dolphinmarineservice.homestead.com/Ign5.html

If the stator windings' resistance values are out-of-spec when cold, or change appreciably after running, the stator is shot.

The CDI-brand line of aftermarket stators would be a good choice for a replacement, have never had one fail yet.

http://www.boatfix.com/searchcdi.asp

HTH & let us know what you find..........ed

 

[twopunches]

Re: stator or switch box?

alright guys this is what i came up with.
i had another diagnostics done.to no avail.everything check out fine.the stator,coils,switch box, compression test.had some advice from this forum to rebuild the fuel pump. i did. well i took it out on a test drive.started running rough again ,headed for the dock.(barley).took home fire it up.chunks of hard alloy was blowing through the bottom carb. (open butterfly)
is my motor shot?cheaper to fix or buy another?why did this happen?is now parts?

thank you all for your help

 

[j_martin]

Re: stator or switch box?

alright guys this is what i came up with.
i had another diagnostics done.to no avail.everything check out fine.the stator,coils,switch box, compression test.had some advice from this forum to rebuild the fuel pump. i did. well i took it out on a test drive.started running rough again ,headed for the dock.(barley).took home fire it up.chunks of hard alloy was blowing through the bottom carb. (open butterfly)
is my motor shot?cheaper to fix or buy another?why did this happen?is now parts?

thank you all for your help

OUCH! sorry to hear that.

Most likely a shortage of fuel leaned it out and burned a piston. The fuel shortage could have been any of about a dozen different things, or a combination of them. On my XR4 there were 7 different faults that all contributed to the problem. The PO knew there was a problem, but never pushed it as he tried to fix it. He gave me a discount to accept the problem.

Second possibility is a severe timing advance, like might be caused by a shorted advance or idle stabilizer module.

For the forum, you always risk that you will grenade your big 2 cycle engine if you keep trying to drive it when it balks. If yer engine balks, back out immediately and go into troubleshooting mode. As you troubleshoot, don't try to run it if it doesn't want to run hoping it'll "clear out".