1971 Evinrude Sportster 25 pumps water for 10 minutes, then stops pumping & overheats

[hhbanks]

1971 Evinrude Sportster 25 pumps water for 10 minutes, then stops pumping & overheats

Hey everyone,

I have a 1971 Evinrude Sportster 25.
It is fine for about 10 - 15 minutes of running at full throttle, but then it stops pumping, overheats, and shuts off.

I imagine the pump is fine since it pumps properly at first.
Just took the motor to a marine mechanic who said that this motor does not have a thermostat...

Does any one have any experience with this model outboard and overheating? Know any steps to take to resolve this issue?

Any insight or suggestions are much appreciated. Thanks!

 

[bonz_d]

If you go to BRP website and look up that engine you will see that you were told wrong and there is a t-stat. Part # is 378065.

 

[AlTn]

the thermostat housing is at the top rear of the block...the cover is that triangular piece held on by 3 screws..the thermostat is under that cover < or should be anyway >...if you want to check it, or simply replace it, just unscrew those screws and lift the cover up and off...the gasket may tear and I'd advise you to replace the rubber seal that goes around the thermostat body too if you go this route. You can just leave the thermostat out for test run purposes just put a washer with a hole in the center in place of the thermostat as some restriction in water flow helps keep the block filled with water. If you've had overheat episodes, your head gasket may need replacing and your head need resurfacing as well.

 

[hhbanks]

Thanks! So you think that a bad thermostat is a likely cause for the outboard to stop pumping after 15 minutes or so?

 

[kbait]

If thermo is stuck closed, it may overheat, but I believe it will still pump water out the back - as when you first start the motor, bunches of water pump out when thermo is closed.

I'd pull the lower unit, change/inspect impeller and inspect pump housing, pull thermo out and blow air up the watertube to be sure there's no obstructions, check out the thermostat function (does it open in boiled water?), make sure the impeller plate isn't bent and is perfectly flat, as impeller seats/seals to it.

Probably faulty waterpump or clogged intake issue, as it actually stops pumping water when running.

Good luck!

 

[Tim Frank]

1) Find a different marine mechanic.
2) Do check water pump. When as it last serviced?

 

[Tim Frank]

.....

 

[F_R]

1. Fire your mechanic
2. Make sure the water pump is as good as you think it is.
3. Pull the powerhead and replace the plastic 313435 water restrictor. Overheating melted it. Happens every time.
4. While the powerhead is off, is a great time to replace the head gasket and exhaust cover gaskets. Overheating damages them and makes them leak.
5. Pray that you didn't run that poor thing to destruction by running hot to seizure. They don't "shut off", they seize and melt pistons skirts.
6. You may have a piece of an old pump impeller floating around in the cooling system. Look for it while doing 3 & 4.

 

[out 2 launch]

It is fine for about 10 - 15 minutes of running at full throttle, but then it stops pumping, overheats, and shuts off.

Are you saying that in fact the water pump stops pumping? Or are you assuming that because the engine overheats that the water pump stops pumping? Two very different scenarios with possibly different causes.

Just took the motor to a marine mechanic who said that this motor does not have a thermostat...

Don't be too quick to judge the mechanic. Is he saying that the motor is not supposed to have a thermostat or that your motor does not have the thermostat installed?

 

[Tim Frank]

Don't be too quick to judge the mechanic. Is he saying that the motor is not supposed to have a thermostat or that your motor does not have the thermostat installed?

Why does that make a difference either way?
If the T/stat was MIA, he should have just replaced it or, at least clearly mentioned it to the OP.
If he did not even know that a T/stat was OEM, then .......