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Johnson4hp 1972 problem

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Aidenmchugh1

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I have recently acquired 1972 Johnson four horse power motor. I am trying to replace the impeller. But I can’t figure out how to get the water pump off. It doesn’t have any nuts or screws. It has two holes going through the water pump but they don’t have anything at the bottom. I think there’s some kind of hidden trick to get it off. Please help
 
Click on the "engine digram" box at the top of this forum page.
Then enter your model number, or the year and Hp, and navigate to the gearbox diagram for your engine.

That should give you a pretty good idea how its all screwed together.

I assume you have removed the gear case and now have it with the drive shaft sticking up through the water pump. Remove the screws that retain the impeller housing and slide it up the drive shaft to access the impeller ( It's best not to pull the drive shaft out unless you are also going to renew the drive shaft oil seal . No problems though if you do).
Watch out for the impeller drive pin.
 
They are a slotted screws. Someone busted them off as Gator mentioned. Soak with Blaster, then heat lightly with propane torch and get a SMALL hammer and tap it.....getting it to move. Then slide it up and off the broken screws.....follow Vic's instructions. Heat the housing a bit if vice grips cant move the screws. Use stainless steel replacements and if heat is used I would consider replacing the shaft seal under the water pump.
Is the paint discolored on the cyl. head? Do a compression test first then. Somebody was after that impeller for a reason.
 
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Aidenmchugh1 said:
Would you know if the screws were Phillips or flathead?
Click to expand...
timguy said:
They are a slotted screws. Someone busted them off as Gator mentioned. Soak with Blaster, then heat lightly with propane torch and get a SMALL hammer and tap it.....getting it to move. Then slide it up and off the broken screws.....follow Vic's instructions. Heat the housing a bit if vice grips cant move the screws. Use stainless steel replacements and if heat is used I would consider replacing the shaft seal under the water pump.
Is the paint discolored on the cyl. head? Do a compression test first then. Somebody was after that impeller for a reason.
Click to expand...

The big problem will be if the screws have broken flush with the top face of the gear-case or with not enough standing proud to grip with vice grips. Machine shop job then to drill them out ?

It would be a good idea to replace the drive shaft seal anyway while the gear case is off


The screws look like this but if the heads are broken off what type they were is immaterial.
0302963.jpg
 
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