1975 25hp Evinrude Overheating

[Harry B.]

I got rid of my old set up and acquired a 25hp 1975 Evinrude. I put in a new impeller and fired it up.
It runs great. Lots of water coming out of the exhaust tube.
It seemed like it was getting hot so I pulled the thermostat plate and pulled the thermostat out and fired it up. Just a tiny bit of water and a lot of steam coming out.
Any suggestions??

 

[racerone]

Is the water in your test bucket 6" or 8" above the impeller ?

 

[oldboat1]

Plastic trash barrel, with water about half way up the leg.... Idle only, or a little above. Can test gear shift but don't rev.

 

[Harry B.]

I've got it in a 55 gallon drum all the way up to the exhaust hole where the water exits (don't know the terminology). There's quite a bit of water gushing out of the hole, but there's a little bit of nothing getting up to the thermostat. She's running way warm........ like freakin hot. Cant run it for very long for fear of it warping or melting stuff.

 

[oldboat1]

Try flushing down from the t.stat. Remove the l.u. and flush up the intake tube. Check the impeller (key dislodged?), check water pipe grommet.

 

[racerone]

Was the water tube installed into the grommet in exhaust housing first.----Or did tube stay in the pump ?-----I was not looking over your shoulder during this work, sorry.

 

[Harry B.]

It stayed in the pump. The brass tube I believe is likely glued/permatexed into the impeller housing.
How would one put a new grommet in the exhaust housing? Maybe it's not sealing well?
The brass tube has no where else to go, so I know it's going into the grommet on the exhaust housing end.

 

[Harry B.]

Try flushing down from the t.stat. Remove the l.u. and flush up the intake tube. Check the impeller (key dislodged?), check water pipe grommet.

It's pumping water so the impeller key is intact and working. It's just not making it up into the powerhead.

 

[racerone]

The tube MUST be installed into the exhaust housing first !!----The grommet in the exhaust housing is easy to replace.----Stop running this motor until you sort this out.----And how can you be sure that it is going into the grommet in the exhaust housing ??

 

[Harry B.]

The tube MUST be installed into the exhaust housing first !!----The grommet in the exhaust housing is easy to replace.----Stop running this motor until you sort this out.----And how can you be sure that it is going into the grommet in the exhaust housing ??

There's no other place for the tube to go due to it's length and placement into the exhaust housing (it would have to bend significantly or bust to go somewhere else and the motor IS pumping water out of the exhaust telltale hole)

So everyone is saying that the grommet in the exhaust isn't sealing properly and the reason for the water not making it up into the power head and it overheating?
The grommet is in the exhaust housing with no room to get much of anything into (maybe there's a super long needle nose plier that can reach it?) so it's definitely not going to be easy to replace that grommet.....aaaand, I cant see a part number on any website for the exhaust housing grommet to even find a replacement............if one still exists.

The shaft is a real bear to get to go back into the powerhead.......likely the reason someone permatext/glued the water tube into the impeller housing.

 

[oldboat1]

Pull off the cylinder head and clean out the water passages around the cylinders -- thin knife or similar. Common with salt water motors, but blockages always possible.

easy to flush down from the t.stat housing. Clean up whatever is at the water pump grommet, and (likely) replace the grommet.

With the lower unit removed, look into the leg under the p.head (need a flashlight). Look for wasp or mouse nests.

edit: and...check and maybe replace the screen at the water intake under the A/V plate.

 

[racerone]

That exhaust grommet is actually easy to replace !-----But if you say it is HARD then I can not help you.----Takes just minutes.----There is something wrong with this motor and in my opinion there is nothing on these fine motors that is hard to repair.-----It was built in a different era and designed to last a lifetime with simple repairs.

 

[Crosbyman]

any fins missing on the old impeller ? yes no ?

...waiting for comment/findings on oldboat1 suggestion... pulll cyl head look/see
(post pictures)

see if you can jiggle a thick mono (weed eater stuff) via accessible passages (thermostat cyl wall water source entry & exit points) try air blasting with proper fittings on accessible openings

work downwards so as not push any blockage deeper in the water cavities
may have to pull the PH if you are getting nowhere ....

did you try sending some city water pressure up the water tube to dislodge any obstruction if the above procedure gets you nowhere ?

can you ask the previous owner if he had high temp issues ...did all this happen when you swapped the impeller ? did you ever test run the engine before the purchase ? was it ok ?

any chance that impeller housing is messed up with that permatex glue ??

good luck with those gremlins

 

[Harry B.]

That exhaust grommet is actually easy to replace !-----But if you say it is HARD then I can not help you.----Takes just minutes.----There is something wrong with this motor and in my opinion there is nothing on these fine motors that is hard to repair.-----It was built in a different era and designed to last a lifetime with simple repairs.

I wasn't looking forward to removing the power head or a bunch of other stuff to do the grommet, but I will since it runs good and so far appears to be worth it to put some time and effort into it......if the grommet has collapsed or whatever causing the overheating issues.

I truely appreciate all your help and suggestions for getting the old girl back on the water. It seemed to operate pretty decent in the barrel, but I have no idea about the lower unit gears quite yet. First things first I guess

 

[Harry B.]

any fins missing on the old impeller ? yes no ?

...waiting for comment/findings on oldboat1 suggestion... pulll cyl head look/see
(post pictures)

see if you can jiggle a thick mono (weed eater stuff) via accessible passages (thermostat cyl wall water source entry & exit points) try air blasting with proper fittings on accessible openings

work downwards so as not push any blockage deeper in the water cavities
may have to pull the PH if you are getting nowhere ....

did you try sending some city water pressure up the water tube to dislodge any obstruction if the above procedure gets you nowhere ?

can you ask the previous owner if he had high temp issues ...did all this happen when you swapped the impeller ? did you ever test run the engine before the purchase ? was it ok ?

any chance that impeller housing is messed up with that permatex glue ??

good luck with those gremlins

There was a tip of one of the fins missing on the old impeller, but it was located right inside the impeller cup.

I found this motor at a yard sale of sorts. It was sitting with the lower end removed. He said the shaft was bent so I was buying it for spare parts while looking for another 25 hp. I assumed that he thought the shaft was bent because it was a beast to get the shaft into the powerhead.
So I did not test the motor at all. I was rolling the dice when I put it back together that it worked (the previous owner said it ran fine, but the shaft was bent as mentioned). The main shaft isn't bent and I don't believe the propeller shaft is either.......but the lower unit was removed when I bought it so I'm not sure what the previous owner's plans were for the motor before he gave up on it.

I'll start by flushing and then if no joy, I'll start tearing it apart. I really have limited time for this project, but I guess I'll find some somehow.

Thanks to everyone so far who has contributed a possible solution. I'll give it a whirl, but it might not happen right away the earliest being this weekend.

 

[oldboat1]

Doesn't seem to be worth your time. If you fix it, post findings.

 

[racerone]

Takes just minutes to change the grommet as stated clearly.----You do not have to remove the power head to change the grommet !!---I believe the upper and lower grommets are the same.----I believe the exhaust housing has 2 wee holes where the grommet is held.----Use those 2 holes to push it out.

 

[Harry B.]

Takes just minutes to change the grommet as stated clearly.----You do not have to remove the power head to change the grommet !!---I believe the upper and lower grommets are the same.----I believe the exhaust housing has 2 wee holes where the grommet is held.----Use those 2 holes to push it out.

I'm going to try to find that grommet online and order it either way due to the water supply issue and since it won't cost much. I plan to get the one replaced that goes into the impeller cup and has the brass tube glued in as well (replace one, just as well replace the other).
So what's the best way to change out that grommet up into the exhaust housing/leg of the motor? I certainly cant fit my hand down in there to pull it out and/or install it.

 

[racerone]

You push it out with a small screwdriver via the 2 wee holes ( 1 on each side ) on the exhaust housing.----It should fall on the floor.--------The factory tool to install it was the diameter of the water tube with a shoulder.----You could make such a tool with wood dowel..-----2 flats on it to allow the grommet to " collapse " as you push it up.---A bit of grease on the grommet helps it go into position.-----Verify that the 2 nibs are lined up with the holes and that is in the correct position.----The actual replacement takes just minutes.

 

[Harry B.]

So I did a little bit of everything that everyone recommended and sprayed water through the thermostat and up the copper tubing after replacing the grommets and stuffing it back into the exhaust tube first. It seemed to not flow well to begin with, but eventually did. Was it plugged?? Maybe, but then again maybe not. I couldn't find any chunks of anything after blowing it out. Either way.........
SUCCESS!!!!
I need to inspect the lower unit, pulll the prop and drain and fill the casing.

The other loose end for me is the choke detent that was broke. For something that appears to be quite simple is frustrating the living &($#) out of me. I cannot get the choke knob through the new detent once it's installed in the carb housing choke knob support piece. Any suggestings with this?????? Those detents are $30 each. $30 for a small piece of plastic that is a nightmare now to find and becoming very rare.