tiller 25 HP heat sensor wire burned

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edmo

Seaman
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Feb 23, 2012
Messages
51
I started out the other day and after going a minute or so with the 1999 Johnson and it when into the SLOW mode I think it's called. sputter sputter run sputter sputter run, etc. Stopped it, shut it off and smelled something burning. The insulation on the heat sensor wire from the power pac (temp. switch assembly) had melted right where it goes into the head. It also melted the grommet going through the head. I dumbly forgot to check the water flow indicator stream from the engine before starting out, but there was a plastic wiring sleeve right next to the melted wire and it was undamaged so I'm not thinking it overheated, but I'm going to check next time. Any ideas?
 
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edmo

Seaman
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Feb 23, 2012
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51
Have been googling SLOW mode issues and find a bunch of possibilities. Will indeed check for overheating, but there were some other meltables in close contact and they are all unblemished. Funny thing, this my newest motor, the first with overheat safeguards, other than a horn on a boat with instrumentation. Before, when the engine overheated it was toast unless I smelled it in time or otherwise got lucky. Guess I need to see if this motor has an oil sensor in the fuel pump and a thermostat if I can't find other cooling issues. The down side of the SLOW issues is that it seems like a lot of people, some with mechanics and some without, threw a lot of parts at it before the problem was fixed.
 
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edmo

Seaman
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Feb 23, 2012
Messages
51
Looked some more at the IPL and looks like the only cooling system parts to fail (other than a clog) are the impellor and the thermostat. If the tell tale stream is strong, guess that would indicate the thermostat, or no?? Any way to check it other than pull the head off and check it out?
 
flyingscott

flyingscott

Fleet Admiral
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Check the impeller pieces may have fallen off the impeller and plugged something up. You only need to pull the waterjacket off to check the thermostat.
 
S

schematic

Lieutenant Junior Grade
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Jan 12, 2008
Messages
1,102
yes, it may have overheated, but you have another problem with the circuitry as well. Overheat should not burn that wire. Only way it can get burnt is if something is feeding the alarm circuit:
-internally shorted warning horn
-wrong or bad wiring
-short in the VRO

once you get the overheating rectified, be sure you have nothing feeding 12v to the tan wire
 
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