40hp Mercury Motor 4-Stroke Help

Hey folks,

While fishing at Peckerwood this past weekend my motor beeped at me after 3 minutes of running and wouldn't stop. Well I checked it out and come to find out water was not circulating through the motor. Knowing that you shouldn't run without a coolant, I relied on my trolling motor.

Anyhow I did well, caught 15 slabs July 3, and 5 on the 4th.

So I took my lower unit off to see if there was in obstructions and none that I can find. So my first guess is to find the impeller that circulates the water?? So my question is: Anybody know where it is? and please don't tell me it's in the motor itself..

Or shall I take to an outboard mechanic and be done with it and stick to repairing lawn mower engines.

Had the same problem on a Suzuki 4 stroke last fall. Checked the inlet on the bottom of the lower unit first. Should be some type of screen over it. Then I went to the outlet and back tracked into the engine following the outlet tube. I ended up finding some trash just inside the motor. I am not a mechanic by any means and it was no trouble. Sometimes dirt daubers will fill up outlet tube. Hope this helps. :)

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Originally Posted by ShimmyShamrock

Hey folks,

While fishing at Peckerwood this past weekend my motor beeped at me after 3 minutes of running and wouldn't stop. Well I checked it out and come to find out water was not circulating through the motor. Knowing that you shouldn't run without a coolant, I relied on my trolling motor.

Anyhow I did well, caught 15 slabs July 3, and 5 on the 4th.

So I took my lower unit off to see if there was in obstructions and none that I can find. So my first guess is to find the impeller that circulates the water?? So my question is: Anybody know where it is? and please don't tell me it's in the motor itself..

Or shall I take to an outboard mechanic and be done with it and stick to repairing lawn mower engines.

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SS, this is for a 25 Yammi but the basics are still the same. Pretty easy job to replace an impeller. YouTube - How to Replace a Water Pump on a 25 hp Yamaha Outboard

More than likely the peep hole is stopped up,you can blow back though with air or a small wire run up the tube.

my stepdad 25hp the peep hole was stopped up by dirt daubers. I used a small wire to run up the tube. that fix it. to bad It knocked me out of a day of fishing.

did you fish pads or is the stumps begining to show ????

Sorry to hear bout your motor. Whats the water level like at peckerwood? Are you launching at the low water ramp yet or the normal one?

I would guess on the 40hp engine it would be like any of the others.

I have a 60 Merc. and a 70hp Force and both of them are the same.

Take the lower unit off and there should be a plastic looking cover that's around the drive shaft that goes up to the powerhead.

If your foot is like mine there are 4 small 7/16 nuts on it and once you remove those you can remove the plastic cover and the impeller is in there.


If yous is like ours then you can't even crank it over without having water to the foot, don't ask how I know, but I have replaced 2 of them on my 60 Merc.

The part for ours is only about $20 bucks and that was at a dealership. I went ahead and bought two.

Good luck with the repair.

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Originally Posted by MEATGETTER

did you fish pads or is the stumps begining to show ????

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Yes, fished the pads since I didn't attempt further out. And, the stumps are visible, about 3" below the surface of the water. You will know it when you run into them :p

Barry, launched at Red Barn. Heard one fella hit a stump and it threw him into the water. Anyways, you can hear boats hitting stumps from across the lake. :eek:

The water not coming out of the pee hole isn't the problem.