25 HP Mercury Outboard Question

I have a 25 HP Mercury outboard and I think it is a ’93 or ’94 but not too sure. Anyway, had it out yesterday and noticed that my pea stream was not very steady at idle. Everything seemed fine with the motor in gear – nice flow but when I would put it in neutral it sometimes slowed to a trickle. Is there anything I can do or check to remedy this?

By the way, fished pool 11 yesterday – didn’t do very well. Managed only 1 keeper, 17″ sauger. Caught another 4 or 5 saugers at 12″ +/- but couldn’t seem to find the big ones. Did see a couple of boats that did O.K. but from what I saw it didn’t look like a great day for anybody.

Assuming you have a functioning water pump, that motor is thermostat controlled. In cold water it will close down and restrict flow keeping your motor warm.

time to replace the impeller. (water pump)

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time to replace the impeller. (water pump)

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Not necessarily true. I have this same motor and recently replaced the water pump. In cold water at idle, I barely get a trickle out of the pee hole. Always been that way, Even the day I bought in brand spanking new!

-J.

Thanks, I’ll bet that is what is going on. I guess it has been awhile since I ran in that cold of water so I had never noticed it before. I had plenty of time yesterday to contemplate potential problems as I sure wasn’t catching many fish.

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time to replace the impeller. (water pump)

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Not necessarily true. I have this same motor and recently replaced the water pump. In cold water at idle, I barely get a trickle out of the pee hole. Always been that way, Even the day I bought in brand spanking new!

-J.

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Don’t know much about that motor. Does it have a warning beep if it gets too hot? How long has it been since you had the water pump serviced? I have always been told to have mine serviced every other year or at least look at it. How often do you guys inspect yours? Having it checked will give you peace of mind and ensure it is in good working order. If you can afford a hundred buck it might be worth your while. Just MHO.

Just had the motor in for a check-up / general maintenance. Replace lube in lower unit, change spark plug and check over. Was told everything looked good but the water pump wasn’t mentioned specifically (I didn’t have my question at that time). To my knowledge there is not a warning beeper, at least I’ve never heard it which I guess is a good thing. Think I’ll place a call to the shop and see what they can tell me. Thanks for all responses.

This motor does not have any warning alarm system.

For what it’s worth, there is no such thing as “checking” the impeller. If I tear into it, it’s getting replaced!

The one I just did was a well worked and 7 years old. Could have gone another 7 IMO!!

-J.

I would just change the impeller. It’s not too hard of a job,or very expensive. Peace of mind is worth a lot.

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I would just change the impeller. It’s not too hard of a job,or very expensive. Peace of mind is worth a lot.

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I am more of the opinion if I tear into I want to replace the wear plates at the same time. I have seen impellers that look good but the wear plates are showing a lot of use.

I have a 25 horsepower mercury 2000 model just got it running good from the carb gummed up…but when i ran it for awhile today the shank between the lower unit and the motor housing got so hot i could barely touch it is this normal or do i have a problem it is peeing perfectly

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I have a 25 horsepower mercury 2000 model just got it running good from the carb gummed up…but when i ran it for awhile today the shank between the lower unit and the motor housing got so hot i could barely touch it is this normal or do i have a problem it is peeing perfectly

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You were running the outboard in a tank of water or attached to a hose fitting to supply cooling water while running it, correct? The exhaust of an outboard is mixed with cooling water, such that that area should never heat up.

No, it is not normal for that area to get that hot. There are lots of possible causes, but first and foremost I hope you weren’t running the outboard dry.

Assuming you weren’t running the outboard without cooling water, this is a tough DIY diagnosis. I would check all the obvious things first. Is it pumping water? Is the exhaust blocked with mud somewhere between the through-prop exhaust, ports, or somewhere else such that the heat is building up?

From there, I think you have to check compression as blow-by could be allowing unburned fuel through the exhaust port.

This could be a fairly involved issue.

Grouse