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Outboard Engine Cooling Problem.

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

Trelawney

Aquatic Womble
Jan 12, 2007
1,126
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I've got a question for all those that service their own outboard engines, as its been annoying me all day.

My 2stroke 15hp Mariner Marathon has been layed up all winter. It ran really rough on its first fire up the other day and wouldn't pump water consistantly. Today. I stripped the carb and gave it a thorough clean. I pulled off the gearbox and cleaned the impellor and pump housing.

The engine runs sweet as a nut and idles perfectly. However, it still won't pump water to the cooling system. It pumped for 5 minutes then stopped and steam came out. The water intake is clear, the tell-tale hole and pipe are clear, and if I blow into the tell-tale pipe, the air bubbles out from the water pump, so the water pipe is clear.

Any suggestions about what to do next? It has a new impellor, and there is no thermostat as its an early 80's engine.

Cheers, Chris
 
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Is the impeller being turned properly/freely by the engine?
Possibly a partial blockage in the cooling system? salt build up would still allow you to blow thru the pipe, but might still prevent enough water flow.
try salt-X on all the parts you can? salt build up would most likely be at one of the hot points.
Any air getting in to the impeller?
 
Thanks Johnny.
The impeller is being turned by the shaft with no problems, and there is no air getting to it.
When I first rebuilt it, it pumped perfectly from the moment it started. I turned it off and tried again and it wouldn't pump. I think I need to re-check the water tube connection to the water pump again.
 
Where does water go when you force it backwards down the tell tale?
Is it making it to the inlet?
 
Thanks for the suggestion Bobdonny. I'm going to remove the gearbox this evening, stick the hose on the water tube inside the leg to see if its reaching the motor. If it comes out of the tell-tale then I suspect it will be a connection problem at the water pump.
 
check the the screen on the lower unit where it picks up the water make sure it is clean, good luck
 
Well, the water made it from the tell-tale to the inlet. Taken the gearbox off (again!) and ran some water the other way, and that got to the powerhead OK. I also injected some watered down brick cleaner into the water intake tube, left it for a few minutes, then flushed it through with clean water. Probably not the best thing to use, but it has cleared something.
Quite a bit of crap came out, mostly salty grit etc. Checked the impeller again, and the water tube connection. All seems good. I'm going fire it up in the tank tomorow and see how it goes.
 
Trelawney said:
Quite a bit of crap came out, mostly salty grit etc. Checked the impeller again, and the water tube connection. All seems good. I'm going fire it up in the tank tomorow and see how it goes.
Click to expand...

does it work now?
 
In a word, No

It still wouldn't pump, so the motor came out and the head came off. It turns out that is does have a thermostat, not that you could see it under all the corrosion and salt cake. The entire cooling jacket was solid corrosion and salt, with all the channels blocked. I'm still cleaning it out, so not sure of the structural integrity of the engine yet. There are some bad pits in the cylinder head water channels. Obviously the original owner never flushed the thing through, ever :rcard.

I gave the thermostat a dunk in brick acid, and its come up like new, so thats something I don't have to buy. Now, if only they made the entire engine block from brass and copper, it'd be so easy to clean.
 
On my diesels I'll flush an acid solution through to clean out all the scale deposits that have built up in the raw water cooling system. It sounds like you're on the right track!
 
Any Update Chris??? Is it possible that the drive key is slipping out of place on the impeller? It would explain the lack of water pumping up the water tube when the outboards ticking over
 
It's all up and running now. It was a right state when it was pulled apart. But it has all been scrubbed, cleaned and new gaskets fitted. Runs perfectly and starts first time.
 
Reactions: scottwilson
Great news Chris

Have some repair rep Ive started tinkering with mine now, cant be doing with paying these outrageous repair bills anymore :head:head
 
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