1960 Johnson 10 hp Ever had one of those days....????

[dockrat100]

Recently finished working on a 1960 qd 10hp, and got it running well in the barrel. Full tuneup....
Took it out on the river, and it did very well..
On the way back, half a mile from the launch, it overheated and shut down...
After a long period of rowing, I did a postmortem on the motor and found all the bolts on the head so seized that they began snapping off, and even then, could not remove the head.
Compression before this adventure was around 60 lbs, compression after was about thirty. Pretty sure my powerhead is fried. :facepalm:


Now, to the question...I have another powerhead for this motor, which has compression of about 55 lbs, but one cylinder seems to leak down about 10 lbs in a minute or so. Cylinder walls are not scored, and the head will come off this block, so compression testing is being done after removing and reinstalling the head over the old head gasket a few times. (Compression may get a bit better after a new head gasket.)

Is the replacement powerhead worth fooling with? Perhaps decarb and run it to see if compression goes up? I have not had to deal with this before, so the next steps are unclear.

 

[Daviet]

Re: 1960 Johnson 10 hp Ever had one of those days....????

Leakdown tests on a two cycle engine are not of much use. If you have 55 lbs compression it should start and run. Your compression might come up some after you get it running properly. You might do a decarb on it after you get it running and see if the compression comes up any.

 

[nwcove]

Re: 1960 Johnson 10 hp Ever had one of those days....????

when you say "full tune up"..did it get a new impeller? only asked that question because puting a new powerhead on , may just result in the same issue. but other than that, id would not hesitate to try the new powerhead....afterall, you do have all the new parts from the old powerhead. (the powerhead still could be ok.....they are tough!)

 

[dockrat100]

Re: 1960 Johnson 10 hp Ever had one of those days....????

Yes, it did get a new impeller. That was the confusing part, I seemed to get a stream from the peehole, and thought I was doing fine, but the passages in the water jacket are apparently plugged up somewhere. After it shut down, I pulled the thermostat cover off, and pulled the starter rope with the motor in gear, and got no water going through the thermostat housing. Something is very blocked somewhere.

Full tuneup for me is impeller, carb kit, and rebuilt magneto.

 

[dockrat100]

Re: 1960 Johnson 10 hp Ever had one of those days....????

Just finished pulling off the old powerhead. I think they never intended for the three half inch bolts holding it on to ever be removed. Does anyone know if the base gasket is the same for Evinrude and johnson 10 hp that year?

 

[dockrat100]

Re: 1960 Johnson 10 hp Ever had one of those days....????

I just installed the new powerhead, and it started on the first pull! It doesn't usually work so easily for me...
After soaking the rings and pistons in penetrating oil, it got to 75 lbs compression. Pretty good, I think.

 

[HighTrim]

Re: 1960 Johnson 10 hp Ever had one of those days....????

I suppose you found out the base gasket is the same.

Did you do the head gasket on the new powerhead? Did you find out what happened to the old powerhead?

 

[dockrat100]

Re: 1960 Johnson 10 hp Ever had one of those days....????

I was going to order the base gasket, but ended up tracing and cutting one, so it didn't matter. I have not done the full post mortem on the original powerhead, since I cannot get the head off. I think the previous owner sucked a clod of mud inside the water jacket, and it hardened there. With no water circulation, the powerhead is a crispy critter.

The new powerhead got the head and powerhead surfaces lapped, and the original head gasket was in good condition, so it was reused. I did use Aviation form a gasket sealer on it to be sure of a good seal. So far, so good.