1958 7.5hp Johnson oil leak

[gmarshall43]

I'm working on this 1958 7.5hp Johnson. It starts up OK but after about 30-60 seconds it starts to run rough at any speed and if I leave the throttle alone, the speed will increase and then decrease and back and forth like that then will eventually stall out and the throttle does not move where I left it. I have replaced the points and spark plug wires and cleaned the carb. I'm getting good spark on both cylinders. I have attached pictures what the water looked like after I ran it last. It looks like oil leaking out. I cannot see any leakage on or around the power head. Can anyone tell what's happening and why does the water look like that?

Gary

 

[doors67us]

Some or most of the oil is , leftover two cycle oil that's unburnt,I experienced the same thing in my 55 gallon barrel,at idle they don't burn all the oil ,like they do at high/higher speeds it's expelled thru the exhaust,I'd get a rebuild kit for the carburetor if you haven't done so

 

[Crosbyman]

half the fuel oil mix probably exists the cylinders during the open phase of the downstroke when both in & out ports are open face to face . The incoming fuel/oil mix pushes the exhaust out but that fuel mix reaches the exhaust ports and goes down into the buckect with some dirty carbon bits. so don't worry

and... at bucket speeds any fuel oil not extracted out the crankcase will pool in the crankcase and get flushed down the bucket via the purge valve... so don't worry

at higher speeds less fuel oil accumulates in the crankcase due to high pressure created during the down stroke.

conclusion... recheck your carb cleaning

btw don't forget you are running a pressure tank... which may not be getting air pressurerized properly due to air leaks... just raise the tank above the engine during your bucket trials if OK then look for a pressure loss in the dual hose system.

if to heavy..... just keep pumping fuel in the carb with the tank push button. see what that does. if engine stabalises ... fuel tank pressure issue to resolve.

great engine...btw

 

[racerone]

Those 56 / 57 / 58 model 7.5 hp run really nice if in good condition.

 

[gmarshall43]

Thanks for the replies. It was interesting reading. I've work on a few motors and have had some oil in the water but not to the degree you see in the pictures. When I began work on this motor, I notice that the hose that goes from the top of the motor to bottom was dry rotted so I replaced it with a similar inside diameter. Doesn't this hose have something to do with the oil?

It was mentioned to get a rebuild kit for the carb. I had cleaned it out and replaced gaskets but still runs the same. Attached is what the carb looked like after a run before this post. There is some fuel there at the edge that looks kind of milky. I will assume that this isn't normal? The fuel in that glass bulb at the bottom of the carb looks good.

 

[racerone]

Yes that hose is for oil recirculation.----And that " milky oil " is very normal.

 

[Crosbyman]

if you plan fixing oldies you should downlaod the bible...where those pages came from

1922-1964 Johnson 302231 Outboard Service Manual

Johnson Outboard Motor Service and Repair Manual # 302231 Tenth Edition covers all Models 1922-1964 .pdf download

watercraftmanuals.com