Johnson A-35 cooling/gas leak

[Waunnaboat]

Hello.  I took out a few motors on the lake today, an A-35 included.  It ran very well for about a minute, but when I adjusted the mixture to be a little richer, it started to suddenly shoot gas a few inches high from the carb float pin/indicator thing.  My best guess at this point is that the motor was overheating, as it did seem a bit hot given that when I threw a bit of water on the cylinder it fizzled out right away.  I believe that the motor overheated, causing the gas in the carb to overflow.  I then shut off the fuel from the gas tank after grabbing a fire extinguisher to keep it in hand should the overflowing gas come in contact with the hot cylinders.  There is no obstruction to the water scoop itself, as a good deal of water came out when I took it out of the water, but I believe that there may be some obstruction somewhere further up the cooling system.  I just acquired this outboard, so I do not know a whole lot about it.  Could there be something else that caused this overflowing?  the gas only went to about the height of the gas tank, so there could be a possibility of some other issue?

"Outboards seem to multiply exponentially..........I find that for every finished project, there are two more waiting to be completed."

[Tubs]

I suspect that the gas squirting out of “carb float pin/indicator thing”, was a result of the motor over heating, building pressure in the gas tank, and you didn’t have the vent open, or the vent is clogged.  

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

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Waunnaboat

[Waunnaboat]

That makes sense.  I did not have the vent opened very much because it was at risk of completely screwing out (may be broken to some extent).  Do you have any advice on what could be causing the overheating?  There was no water coming out of the muffler, where I assume would be the exit point for water on these motors?

"Outboards seem to multiply exponentially..........I find that for every finished project, there are two more waiting to be completed."

[stanley]

You won’t see water exiting anywhere,especially not from the muffler.The A35 was the first Johnson to use the pressure siphon system.When running motors with this system it is important to get them up to speed pretty quickly to get the water flowing and then you can throttle back if you want.The usual culprit for over heating is rust  flakes in cylinder cooling passages forming a clog at the elbows or tee fittings.

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Waunnaboat

[Tubs]

 

Don’t try removing the fittings from the cylinders. 90% of the time they just snap off.    

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[Waunnaboat]

I have just checked via the portion of the motor that can be taken in two with the LU attached to the driveshaft.  There is no obstruction inside of the LU or powerhead, so I suspect that it was not getting up to speed as Stanley said.  Next time I’m out on the lake I will make sure to open the air vent and get up to throttle right away.  I was only running it at 3/4 speed max when it overheated, so that would be a sensible reason for the overheating.

"Outboards seem to multiply exponentially..........I find that for every finished project, there are two more waiting to be completed."

[Tubs]

Be sure the vent hole isn’t plunged.   

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

1 user thanked author for this post.

Waunnaboat

[putzer]

Another item that could be causing an overheating problem on an A35 is a worn or damaged prop.  It is the prop that forces the water into the cooling system and if the prop is worn or damaged, it limits the flow into the system itself.  Good luck, the A 35 is a sound and fun motor, enjoy it.

[Waunnaboat]

The prop is actually in pretty good shape, considering its age and the condition of the rest of the motor.

"Outboards seem to multiply exponentially..........I find that for every finished project, there are two more waiting to be completed."

[Author]

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