What’s the danger?? I have heard some people say you can, some say you can’t. I have a '94 Johnson 140 v4 carburated engine that runs like a champ other than it has beem overheating at high speeds. I have replaced the water pump, impellar, replaced thermostats, back flushed with a water hose, been to two mechanics, blah blah blah anyway i took the thermostat housing off and noticed it was a little trashed up with debris and shells, went ahead and pulled them out, ran it down the river wide open today for a solid 20 min with no alarm, no limp mode, the water coming out of the pee hole was luke warm like it should be. Can i just leave them out or is it necessary to put them back in?
FISHBOY; I’VE BEEN TOLD THAT RUNNING WITHOUT T-STATS CAN CAUSE OTHER ISSUES LIKE OIL CONTAMINATES DUE TO ENGINE NOT GETTING WARM ENOUGH TO BURN FUEL EFFICIENTLY… IF ENGINE IS HEATING AT HIGHER SPEEDS I SUSPECT YOU HAVE INTERNAL COROSION CONTAMINATES BLOCKING COOLING SYSTEM ;;PROBABLY TIME FOR A DEEP CHEMICAL FLUSH !!!
George McDonald US Navy Seabees,Retired, MAD, Charleston Chapter [http://www.militaryappreciationday.org
When you see “Old Glory” waving in the breeze, know that it is the dying breaths of our fallen hero’s that makes it wave.
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So what would be the best chemical to use?? I have used salt away with no success. Acid? Barnacle buster? Can i run it through the muffs or do i have to remove lower unit? Also would it have blockage if it didn’t overheat with no t-stats?
FB, you mentioned you found trash when you removed thermostats and cleaned it out. Then no overheat issue. Sounds like problem solved, so put therms back in and try it. As Gail mentioned, there is a reason for them.
Good luck.
NN
FB ; I USED RYDLYME IN MY 90 4STROKE YAMI , CLEM RECOMENDED IT AND I WENT ON AMAZON AND PURCHASED A GALLON ;; APPROX 50 BUCKS … I PULLED LOWER UNIT SET A TUB UNDER POWER HEAD, COMMECTED PLASTIC TUBEING TO TUBE GOING INTO POWER HEAD AND PUT A OLD AQUARIUM PUMP TO TUBEING AND PUT CHEM IN TUB WITH 3 GALS WATER , CIRCULATED THRU MOTOR OVERNITE , COULDN’T BELIEVE THE CRAP THAT WAS IN TUB WHEN FINISHED ;;;; HAVEN’T DONE A SEA TRIAL YET BUT I KNOW ITS CLEAN INSIDE SO IT’S GOTTA RUN COOLER … BTW I DID REMOVE THE T-STATS BEFORE CLEANING AND INSTALLED NEW ONE ;; I’LL POST RESULTS LATER… IFFN YOUR INTERESTED IN THE RYDLYMR BE SURE TO GET THE MARINE GRADE !!!
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George McDonald US Navy Seabees,Retired, MAD, Charleston Chapter [http://www.militaryappreciationday.org
When you see “Old Glory” waving in the breeze, know that it is the dying breaths of our fallen hero’s that makes it wave.
author unknown
George McDonald US Navy Seabees,Retired, MAD, Charleston Chapter [http://www.militaryappreciationday.org
When you see “Old Glory” waving in the breeze, know that it is the dying breaths of our fallen hero’s that makes it wave.
author unknown
My boy just showed me this new thing that just come out,it’s called google,I typed your question in and got some great explanations on why you need thermostats.Sounds like your mechanics ripped you a new one .I’m with NN,try the old t-stats and if that doesn’t work ,go buy some new ones yourself.Good luck,I think you found the problem.
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I’d put em back in. Very hard to warm a lake or ocean to operating temp with your boat motor. In a car you’ll usually warm up the water and in some case flow the water Too fast to cool proper in the radiator and over heat. We don’t run thermostats in our race engines but do install a 5/8" restrictor plug to slow flow down. Like DoubleN said, sounds like you found your problem. I would at a minimum at least put in new thermostats for a piece of mind.
My old 2smoker is a 1995 Johnson 88spl. Similar vintage. Given what you’ve done so far, I suspect your cooling passages may look like mine did. I had a bad piston/cylinder (unrelated to cooling, I think) and in pulling the head off I found this.
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You’re looking at the back of the head. The cover plate is leaning away from the motor with most of the gasket stuck to it. They actually cleaned up just fine with a brass wire brush in a drill motor.
If your motor is generally put together the way mine is, you’ll have a cylinder head cover that bolts straight onto the back of the head. There is a heavy gasket between the cover and the head and cooling water passages on both sides of the gasket. When I pulled mine, I could not believe how full of salt/corrosion it was. Can’t imagine how it was cooling itself. The other side was the same way.
Caution: getting the bolts out of that cover to clean it and replace the gasket is a really dicey trick. With motors this old there is a real possibility of twisting bolt heads off. Ask me how I know.
All that to get to, I’d try the flushing trick with some kind of de-scaler. And, do it for a LOT longer than you want. While it is flushing, maybe tap lightly on the outside of that head cover to try to loosen some of the crap that may be in there.
Note - I flush my motors religiously when they come out of salt water. This was a well maintained motor that had that much build up in the cooling passages.
If you’re feeling froggy and want to pull those covers, be very very patient with the bolts. I used a small hand held propane torch to warm the head/block areas around where the bolts went in. Lots of cycles of warm an area, shoot with PB Blaster, wrench gently to get the bolt to move. Then, patiently, maybe 10 degrees turn at a time, spin the bolt out some, PB Blaster, spin the bolt back in. Spin bolt out some and repeat. Each spin cycle, tap
I had a 2-stoke Yamaha 1997 90hp that had same issue. Old school fix… remove the “guts” out of the thermostat and reinstall the shell, this keeps the correct amount of backpressure and NEVER gets stuck again. Learned this from commercial fisherman (crabbers) that are running their equipment in puff mud, also discussed with three Yamaha mechs. they said that’s the way to do it. It worked and never had overheat issues again! Also did this on my pathfinder boat 2004 225 Vmax that I was in the shallows all in bulls bay alot. Not sure about the new motors to much computer stuff. 
Kencraft 23T twin 175f Suzuki's
Kencraft 23T twin 175f Suzuki's
Thanks for all the helpful input. I will put new thermostats in and water test and see what happens. I don’t really want to take cover off heads but will so as a last resort.
This reminds me, I have a weak stream on my jon boat outboard. Water pump is fairly new so i am guessing its probably time to pull t-stat again. (have to pull and replace every couple of years despite fresh water flush after every use) May try and clean this go round instead of replacing. What chemical works best that will not be detrimental to the to the t-stat materials? I see someone here had recommend Rydlyme but I don’t want to buy a whole gallon for such a small job. Plus I am not certain if that might not be too harsh for the t-stat itself. I tried PB Blaster one time but seems like that did not work well. Does vinegar work? How about tonic water or club soda? Any ideas on household chemicals or something i can grab from hardware store?
This. Thermostats are planned obsolescence and something else to fix. Sure they make the motor work more efficiently as far as “perfect” operating temperature…when they crap out 40 miles offshore…not so efficient.
The ENTER-NET Fisherman
MY MECHANIC SAYS RUNNING W / NO T-STAT WILL CAUSE THE LACK OF PROPER TEMP IN HEAD AND ON A 4BANGER CAUSES THR OILL TO COLLECT MOISTURE AND WILL TURN OIL MILKY,DECREASING IT’S LUBE ABILITY… COULD BE A VERY EXPENSIVE PROPOSITION , I CHOOSE TO DO IT RIGHT…
George McDonald US Navy Seabees,Retired, MAD, Charleston Chapter [http://www.militaryappreciationday.org
When you see “Old Glory” waving in the breeze, know that it is the dying breaths of our fallen hero’s that makes it wave.
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