110 johnson overheat

Bogus

Cadet
Joined
Oct 4, 2010
Messages
11
Evening all,i have a 110 johnson, J110TLCEM, have not had the boat all that long but has been running fine up until today, unfortunatley we had to return to the boat ramp at dead low tide which saw us runn through some mud to the extent that it covered up the water intake for a short time, (less than a minute at 5 knotts),this caused the overheat alarm to come on,after waiting for the tide to rise enough to get the boat on the trailer we half loaded it and started the motor before we lifted it out of the water, started fine,a black muddy stream ran out the tell tale for an instant and them ran clear....no overheat alarm at all....fine i though, not the best practice but all was good .. i thought...once home put the muffs on and planned on giving it a good flushing out given the crap it had been in.....after about maybe 2 minutes on comes the overheat alarm and the water is getting hotter than normal...shutt down engine.....all this time the tell tale was pumping as strong as ever....could it be possibly something bloke or got crap in it?, maybe thermostat???...any help would be greatly appreciated ..Cheers Brian...
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: 110 johnson overheat

T stat may be blocked. Pull it and inspect, then while it is off flush/backflush the cooling circuit.
 

SparkieBoat

Captain
Joined
Aug 17, 2009
Messages
3,643
Re: 110 johnson overheat

yep..drop the gear case, replace the water pump impeller, remove the t-stats and back flush before replacing the gearcase.
 

Bogus

Cadet
Joined
Oct 4, 2010
Messages
11
Re: 110 johnson overheat

thanks for the replies , really appreciate it, just another question... where would i find the T Stat ? and is there one or 2? ..thanks again for your help...
 

Bogus

Cadet
Joined
Oct 4, 2010
Messages
11
Re: 110 johnson overheat

ok so i have the thermostats out, there was a fair amount of silt/sand in the housing and through the T/stats...interestingly i tested both t/stats starting in cold water right up to boiling...no opening at all....seems a little odd they both don't seem to be working, will get some replacements fitted and hopefully will be back in business...is there any point in removing the exhaust housing above the t/stats at all???or is that after the fact...thanks again for yourhelp....
 

Haffiman

Commander
Joined
Dec 17, 2009
Messages
2,454
Re: 110 johnson overheat

During my years as OMC dealer I noticed something 'funny' about T-stats. I never encountered an OMC T-stat that stayed shut (did not open), they normally either stayed open or 'lost' the top. However Yamaha and Sierra T-stats reacted the opposite. They did not open, but stayed shut when failing. The results were that with a failing OMC thermostat the engines ran cold, with the other they overheated. I always used the OMC originals, better a cold engine than a melted engine.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 110 johnson overheat

I wouldn't pull the exhaust covers unless you think water is getting into the exhaust cavity and into the lower cylinders during operation. If you have debris/muck all the way back to the thermostats, you may have more internal to the powerhead. Might want to pull the head covers off both heads and see if the head passages are also plugged up.
 
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