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Got my motor running and it seemed to run just fine on shore. Revved up just fine

So I put the 13 in the water and took out for a test spin. It seems to be OK in the lower revs but bogs down terribly when I apply any throttle. No power, can't even get it up on plane. Checked the tank and fuel bowl for air intrusion and couldn't find any.

Any ideas on what to look at?

Thanks - John

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my performance problems with my 25 Merc seem to be fuel related. 1st pass would be to verify that your tank is properly vented and your fuel line flows fine. Next would be to determine that you are running clean fresh fuel - especially no ethano depending on the age. Lastly - run some seafoam through to clean up the fuel system and carb.

i just did this - new fuel, pure gas and seafoam - my motor runs better than new - all bogging and idling issues disappeared in 10 minutes.

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Could be any number of things. Bad gas, losing spark, fuel restriction just to name a few. Are you sure it's running on both cylinders.

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OK - here's what I have. Carb has been rebuilt and seems to be fine. Revved up fine using the fast idle lever. I borrowed a known good working gas tank from a friend and nothing changed.

At some point I thought maybe the best thing would be to get some professional help so I brought it into the shop for the mechanics to take a look at. They saw the same performance I did. So they did some basics like adjusted the timing, idle speed etc and all of a sudden it started running fine! But - the mechanic wasn't so sure that it wasn't an underlying intermittant electrical problem that caused the problem(stator, trigger, switch box). He said run the heck out of it and see how it does, bring it back if it starting badly again.

So I ran it home and it seemed to run great. Started right up, got up on plane and ran like a top. Excited to take the kids out for a spin, I got them out on the boat and went to start it up and it cranked but wouldn’t start. Checked for spark and got nothing to either cylinder.

So today I checked the various components with my ohm meter and got the following:

Trigger – 750 ohms (acceptable range 650-850)

Stator –
B/W wire to ground – 48 (acceptable range 120-180)
B/Y wire to ground – 2649 (acceptable range 3200-3800)
B/W wire to B/Y wire – 2581 (acceptable range 3100-3700)

Unless I’m reading something wrong in the service manual, the stator seems to need replacing. Thoughts?

Switch box can’t be checked, you just have to see if all the other components read good. If they do, replace the switch box.

Didn’t check the coils because I thought that the chance of both of them going out at the same time was pretty slim…

So – that’s where I am at this point. Thanks for the help guys…

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I'll bet your losing a ground somewhere.

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Would a bad ground give me false resistance readings?

Know where the ground for the stator is?

Thanks...

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Second what Duane says. Check and clean all the ground connections to the block, and if that doesn't do it, then check and clean all the connectors on the powerhead.

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Depends on If you are trying to read thru it. If so, absolutely.