Big trouble 1994 Johnson 40 horse

[purplesage]

This is the motor that had the thermal runaway. I tried to follow the advise I recieved on this forum. I rebuilt the water pump - changed the lube in the lower unit. I then filled a tank and started the motor. It ran well for about two minutes at approximately 600 rpm. The telltale was shooting water at a good rate and all seemed encouraging.
Then for what seemed to be no reason the motor backfired and stopped running. Now it will not turn over at all. It feels like for all intent and purpose that it is ceased.

I haven't pulled the head but I did pull the plugs and spray in some oil. The fuel was well mixed 50 to 1 and I had not shifted the motor.

Any thoughts or advice? Pretty discouraged at this point. Jon

 

[boobie]

Re: Big trouble 1994 Johnson 40 horse

Did you crank it over and see if there was any water in the cyl's ?

 

[purplesage]

Re: Big trouble 1994 Johnson 40 horse

Can't crank it over - it seems to be ceased. I guess I will spray some oil in the cyl's and let it set for a couple days to see if by any chance it will loosen up. Don't know what else to do.

 

[ONERCBOATER]

Re: Big trouble 1994 Johnson 40 horse

when you say will not turn over at all do you mean that the engine seized (as in flywheel/crank/pistons do NOT move at all?)or that it will not fire and run?
the oil in the cylinders is a good idea.... I assume that the 40hp in question is a twin cylinder with single carb... so you could not have a cylinder that got NO lubrication....errr that is unless your reeds did not function correctly..(bent leaf/something stuck in them/ or stuck shut from varnish) that might cause you to have no lube on one piston and seize.
You said telltale was shooting water.... did you by chance put hand on block while running or when she shut down to see if block was hot ...perhaps you have a plugged water jacket and it heat seized?

Sean

 

[dew2]

Re: Big trouble 1994 Johnson 40 horse

Have you tried to turn the flywheel by hand? If that dont turn it remove the head.

 

[purplesage]

Re: Big trouble 1994 Johnson 40 horse

It is a 2 cylinder - twin carb. I did not put my hand on the block. It was running so nicely that I initially thought I had a dead battery and that was why it was not starting. My first clue it was more serious was when I went to change the battery and found the battery terminal hot. Since then I have been trying to turn it by hand with no success.

 

[SeaKaye12]

Re: Big trouble 1994 Johnson 40 horse

It is possible that the seizure is in the lower unit? Maybe the "backfire" was something in the gears locking up?

You can remove the lower unit and see if the flywheel would then turn....

Not likely I suppose; but possible.

Chuck

 

[boobie]

Re: Big trouble 1994 Johnson 40 horse

Agree with SeaKaye.

 

[purplesage]

Re: Big trouble 1994 Johnson 40 horse

Could this happen even when not in gear?

 

[ONERCBOATER]

Re: Big trouble 1994 Johnson 40 horse

yes it can

 

[purplesage]

Re: Big trouble 1994 Johnson 40 horse

We'll you guys were right - I pulled the lower unit off and the motor turns over nice as can be. Obviously when the thermal runaway happened it chewed up something in the gear case. Now the $64,000 question. Is rebuilding a lower unit something a guy like me can tackle or is it something best left to a shop? Some of you that have rebuilt them might give me a comment or two about its difficulty. Also, I drained the lower unit lube (which I had just put in there last week) and the were a fair number of metal shavings.

 

[kevin11mic]

Re: Big trouble 1994 Johnson 40 horse

you can do the rebuild...there not to difficult but they can get pricy...depending on whats wrong you might be able to save some of the parts..dont know till you pull it appart

 

[boobie]

Re: Big trouble 1994 Johnson 40 horse

Pull the g/c apart and see what you find and get back to us.