1957 johnson 7.5 lower unit leaking

[josh9676]

I went to change the lower unit lube in 1957 johnson outboard, and when i pulled the plug, mostly water came out with a little bit of sludgy looking stuff. I was wondering where it would be most likely leaking from... i put lube in it and it hasnt leaked any of it out, so i am guessing its somthing internal. When running it last year i noticed that the water that was coming out of the motor was quite warm, and i just wanted to know if that is normal. Thanks alot guys!

 

[Mas]

Re: 1957 johnson 7.5 lower unit leaking

It may be as easy as having not replaced the fill/vent seals...or worse. Get the the LU pressure/vacuum checked.

You may have to reseal the LU if it's not the event/fill.

MAS

 

[jbjennings]

Re: 1957 johnson 7.5 lower unit leaking

You are going to have to pull the powerhead (not as hard as it may sound, only 2 fuel lines and about 6 flathead screws with a well-fiitting screwdrivier) then disconnect the shift shaft, then undo the lower unit to midsection bolts and drop it. Change the water pump impeller. In the summer, the water coming out the exhaust relief should be a little warm mainly because it's mixing with hot exhaust. But not hot. If so, not enough water is getting to the powerhead. Either way, if you can't put your finger on the cylinder head and hold it there for 3 seconds after any distance wide-open throttle run, then it's getting too hot.
Now you're going to have to reseal that lower unit. Just get a seal kit and replace them all. The shift shaft seal is a common culprit and you'll probably have to ask how to get it out (o-ring under a bushing), but we can help you on that, as well as how to get the old seals out since the propshaft is often a culprit as well due to fishing line behind the prop. Once you get it resealed you'll be in good shape. If you keep running it with water you'll ruin your drive shaft bushing and possibly driveshaft and then need a new lower unit housing. You're about to get a real education on the joys of old outboards, but fear not---that's a great motor and fun to work on once you learn the basics. I got my education on a '55 7.5 evinrude from the guys on this forum just a couple of years ago.
The good news---the seal kit is cheap. The clutch dog and gears that are expensive and hard to find must be in good shape on your motor or you'd be complaining it's jumping out of gear on you.
Need a parts diagram, we can do that, too!
Then again, maybe you may want to find a mechanic that'll work on a motor that old.
good luck,
JBJ

 

[Wazaa_opihi]

Re: 1957 johnson 7.5 lower unit leaking

id also look at the seal on the prop shaft i dont know about things in your location but here in my town when you return in the harbour you have to go under a bridge and we always use the space on the left for returning and there is ALWAYS some dummy that is fishing under the bridge with his line going right in the middle of the lane and i dont know how many times im comeing in i have to kick my engine in netural to prevent my prop getting tangled ...well one of my costomers wasent as observent as i am i guess and got a ton of fishing line caught in his prop later when i went to service his honda outbords i found the prop shaft seal was wasted due to tons of fishing line that had gotten between the shaft and seal his lower unit lubricant looked about the same as your description you just gave

 

[lindy46]

Re: 1957 johnson 7.5 lower unit leaking

Yeah, after the fill/vent plug seals, the propshaft seal is the third most likely culprit. Best to pressure test the lower unit to be sure though.

 

[josh9676]

Re: 1957 johnson 7.5 lower unit leaking

Ok i think the fill and vent seals are probably ok, because when i drained the oil, i looked at them and they look brand new. I am planning on changing the impeller, and that comes with some seals and new gaskets ( http://www.vintageoutboard.com/Thumbnail/18-3001C.JPG ) This is a picture of the set, it is $31.90. Would one of those likely be the culprit, or would it be farther down in the lower unit? How would i go about pressure testing it as well?

 

[Mas]

Re: 1957 johnson 7.5 lower unit leaking

How would i go about pressure testing it as well?

You can buy the pump w/gauge...or just take the LU to a marine shop...they can do it pretty cheap.

MAS

 

[lindy46]

Re: 1957 johnson 7.5 lower unit leaking

Ok i think the fill and vent seals are probably ok, because when i drained the oil, i looked at them and they look brand new. I am planning on changing the impeller, and that comes with some seals and new gaskets ( http://www.vintageoutboard.com/Thumbnail/18-3001C.JPG ) This is a picture of the set, it is $31.90. Would one of those likely be the culprit, or would it be farther down in the lower unit? How would i go about pressure testing it as well?

You need to purchase a seal kit for the lower unit - the one you have is a water pump kit only. The L/U seal kit will include a prop shaft seal and O-ring, a drive shaft seal, an O-ring for the shift shaft, 2 seals for the drain and overflow bolts, and a spaghetti seal for the halves of the lower unit.