Home › Forum › Ask A Member › Need help with later model Merc 25HP two stroke ignition system
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fleetwin.
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August 9, 2025 at 9:37 am #298811
A relative on the west coast has a larger boat with a 120hp force along with this 25hp merc auxiliary engine. Horrible combination, I know. The 25hp is a remote electric model with its own controls/key switch up at the console, another horror story. I’m guessing the Merc is a 90s model, it has a silver strip around the cowl, I can get its serial number if that will help.
In any event, he killed the started motor trying to get it to fire up, and insists it has no spark. Insists that all safety switches are properly positioned. Being an OMC guy, all I can do is troubleshoot this kind of ignition like it is an OMC. So, the first thing I would do would be to eliminate the “stop circuit”. Need, less to say, I know nothing about the Merc wiring or how to find the stop lead coming from the key switch back to the engine’s “switch box”. I’m hoping this lead has a screw connection to the switch box so it can easily be removed to check for a faulty stop circuit.
So, am asking for guidance here, that I can hopefully relay back to my brother inlaw, so he doesn’t spend big bucks guessing, and replacing good parts.
Thanks
Don
August 12, 2025 at 7:15 am #298872Sorry, Don…I just saw this now. I don’t visit this site too much anymore. 25s were not that common in my area, back when I was gainfully employed fixing two-stroke Mercs. A serial number would be good. I still have most manuals. Usually, two stroke Mercs will have the stop wire the same color as OMC…Black/yellow.
Long live American manufacturing!
August 13, 2025 at 1:32 pm #298922Thanks Bill! I did figure out that the stop wire has that same color code as OMC/ black with yellow tracer. My brother inlaw disconnected the stop lead, got spark, then found that the stop lead had been melted/shorted to the block, so the engine is running again. But, I am sure there will be more issues, he is a nice guy, but tends to wreck stuff fiddling around with it.
Now that I look at a picture he sent me, looks like it is a 9.9hp, not a 25hp. Looks like the serial number is: DL 266900.
I can email a picture of the engine if that will help, probably won’t post here due to size.
Thanks buddy, hope all is OK.
don
August 14, 2025 at 9:12 am #298960Thanks Bill! I did figure out that the stop wire has that same color code as OMC/ black with yellow tracer. My brother inlaw disconnected the stop lead, got spark, then found that the stop lead had been melted/shorted to the block, so the engine is running again. But, I am sure there will be more issues, he is a nice guy, but tends to wreck stuff fiddling around with it.
Now that I look at a picture he sent me, looks like it is a 9.9hp, not a 25hp. Looks like the serial number is: DL 266900.
I can email a picture of the engine if that will help, probably won’t post here due to size.
Thanks buddy, hope all is OK.
don
Don if you want….always feel free to email me a picture that needs re-sizing to post here. Just takes me a second and I’ll e-mail the smaller version back to you
August 14, 2025 at 11:52 am #298965Thanks!! I just can’t seem to figure it out. Don
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