03 Mercury 25hp 2stroke issue - model 1025301AD

[NLaudy]

I have been very luck in the fact that I haven't had many engine issues since I bought this boat last year. Well Saturday morning I was on the water doing some trolling when I heard a steaming noise and looked back to see that my motor was no longer peeing and steam was rolling out of the pee hole.

I turned the motor off and waited a few minutes and turned it back on and it started peeing again. So I started trolling again (this time back towards the boat ramp, lol) and after about 4 minutes it did the same thing (quit peeing and steam started coming out) so I shut it off immediately.

I trolled for a good hour back towards the ramp with my trolling motor and decided to give it one more test before loading it to go home. It started peeing right away and within a few minutes the pee turned to steam. I shut it off and loaded the boat onto the trailer and went home. Since I was in brackish water I wanted to flush it when I got home and hooked it up to the hose. It started peeing like normal and I couldn't reproduce the issue with it hooked up to the hose.

Does anyone know what kind of issue this sounds like? I pulled the lower unit off to look at the impeller and stuff and it looks okay to me but to be honest I don't have much knowledge when it comes to boat mechanics.

Below are a few pictures I took.






Does this look normal? Not sure what all this is? I rubbed my finger on it so that is why it looks smeared in the one spot.

 

[nccatfisher]

When you have it on the hose you are forcing water through it. When it is in a barrel or in the lake/river it has to pump water. Replace the impeller and all O-rings and it should cure the issue.

Make sure and blow out water intake ports and check for obstructions while you have it apart as much as possible also.

 

[crazymanme2]

In your pic that smear is unburned oil,normal.Check thermostat when clearing system.Sounds to me like an obstruction in the cooling system.

 

[JMichael]

The impeller doesn't appear to have any broken fins and its not so old and stiff/hard that it's staying curled once it's removed from the pump housing so I don't think it's an impeller issue. I'm thinking along the same lines as Crazymanme2 and would check out the thermostat and look for other obstructions in the water path. If it were me, I'm probably try removing the thermostat completely and testing it like that. If that cures the problem, then you could get a new thermostat.

 

[WaterWaif]

Its apart so new impeller.
On mine impeller looked fine as far as rubber,however the bushing inside was ground off almost through on one side(edge).Maybe compare inside dimensions between old and new on yours in case shaft could spin inside?

 

[NLaudy]

Thanks all! I ended up ordering a new waterpump assembly and a thermostat. Figured I may as well just replace it all since I have it apart.

 

[crazymanme2]

Those are good motors,I have a 99 that has treated me well over the years, other than a charging issue that I cured with a $8 Radio Shack part.