I have a 130 Yamaha that had an overheat problem. I replaced the thermostats. One was stuck closed and one stuck open. That did the trick for a week until it overheated again. So off came the heads and cleaned all the jackets, new water pump, new t-stats, drained all the gas, new fuel water separator.
Put everything back together and started it up on the hose. No time to drop in the water. Seemed like the starboard side head was hotter to the touch then the port. So it led me the thinking about leaving the t-stats off. What are peoples thoughts?
if you leave out the tstats, the engine will not reach normal operating temp, especially in the cooler months.
engine may idle higher, cause excessive wear in the gearcase.
engine may run rich, fouling plugs and causing excessive carbon build up, which can cause ring sticking, high and or low compression, and mechanical failure.
get a laser thermometer and take the motors temp so you KNOW what the temps are, and fix the problem.
sounds like you are a very capable mechanic, and this kind of job isn’t parts expensive, mostly labor.
I always boil my thermostats, new or old. If I am just replacing the gasket, I boil again.
I boil a thermostat that I am replacing and watch the temp when it opens up. Then I boil the new one. All it takes is one time for a new thermostat to stick and that $5 part just cost thousands.
My $.02
Did you check to old ones?
quote:Originally posted by penfishn
around every bend theres the promise of a treasure that can only be caught and seen in a blink.. and in your minds eye..and sometimes if youre lucky..in a picture..its there for just a minute...then gone..but hopefully once youve seen it it will remain in your heart forever. Theres nothing like the "Smell" and sounds of the creek. Its not just one thing that makes it familiar..its all of it.
Not yet. Going to get laser out this evening and drop it in the water. I’m wondering if the motor is running rich. I pulled the carbs and cleaned, ran a decarb then put some new plugs in. After 5 hours and they had some carbon built up on them and the plugs were black.
My 1998 115 Yamaha overheated at high throttle speed and I also cleaned the head, water jacket and tstats but I also changed the poppet valve to the new design. Works fine now.
I changed that too. Went to launch the boat today and my break line had a whole in it. Thank god I pulled the boat out in time, as the breaks gave out at the top of the ramp.
I saw a post here not too long ago about running a motor in a tub with vinegar to clean water jackets. Not sure if this will work in this case, but just wanted to put it out there.
My thoughts, worth only what you payed for them. If the engine didn’t need thermostats, the manufacturers would not go to all the trouble and expense of making them with thermostats. The engine needs to maintain a specific temp range to run efficiently. Not too hot, not too cool. Just like a car. Removing the thermostats to keep the engine cool is just hiding the cause of the problem and not correcting it.
Capt. Larry Teuton
Cracker Built Custom Boats
“Ships are the nearest things to dreams that hands have ever made.” -Robert N. Rose
If I had an older motor where parts aren’t easy to come by, and it was a beater-up, I wouldn’t bother with the thermostat. On a newer motor that I plan on using for the next decade, I’d definitely keep thermostats in it, unless the ONLY options I had were to buy questionable-quality parts. Apparently some models are known for having sticky thermostats and (perhaps) there is no way around it other than just leaving the t-stat out and dealing with any side effects.
My old 7.5hp didn’t have a t-stat in it when I bought it, but it didn’t seem to effect it any.
“Sire, it belongs in truth to the Church of God, in whose name I speak, to endure blows and not to inflict them. But it will also please your Majesty to remember that she is an anvil that has worn out many hammers.”…Theodore Beza
I would usually agree that maintaining a piece of equipment according to the manufacturers design is the best route. But, I run a 1995 Johnson 88 spl(essentially a 90). I rinse her with fresh water on the muffs religiously after every trip. I had a series of thermostats corrode shut that led to over heating. It happened once, so I replaced them. Ran one year fine. The second year, she started overheating again. Since the stats weren’t that old, I assumed water pump. Rebuilt it. No improvement. Pulled the stats and they were both corroded shut, again. Replaced them. Two years later, over heating again. Went straight to the stats this time and, again, they were nasty. I hate the idea of heating a motor up to the point that the buzzer goes off. She might tolerate a little bit of that, but, I hate doing it repeatedly. So, I did some research and decided to just leave them out. The book specified a spark plug for cooler conditions, so , I swapped to those plugs.
That was 6 or 7 years ago. I’ve thought about trying a new set of stats, again. But, after buying 2 sets that crapped out that quickly, I decided, I’d rather run a little cool, and maybe rich and avoid overheating the old girl again.
That having been said, I would not go this route unless all other cooling system maintenance is up to date and your sure the stats are the bad link.
She runs pretty well and, if she gets synthetic 2-cycle oil, she is pretty slow to load up and start stumbling at idle. With organic Dinosaur oil, she loads up within a a few minutes. So, she gets the high dollar stuff.
I’ve got a Skiff with a suzuki 40 on it. I love to take it in the shallows and it takes only a little mud to hang the thermostat and I’ve had it run hot once or twice. I pulled the stat and was very happy with it until winter came. Boat ran like crap and idled terrible. I try to stay off mud flats and run the thermostat.
I saw a post here not too long ago about running a motor in a tub with vinegar to clean water jackets. Not sure if this will work in this case, but just wanted to put it out there.
Good luck.
Ken
I saw that post and started doing it, the water is nasty every time I do it now, it get a ring around it. I would guess that is works since it did not do that before. :smiley:
quote:Originally posted by penfishn
around every bend theres the promise of a treasure that can only be caught and seen in a blink.. and in your minds eye..and sometimes if youre lucky..in a picture..its there for just a minute...then gone..but hopefully once youve seen it it will remain in your heart forever. Theres nothing like the "Smell" and sounds of the creek. Its not just one thing that makes it familiar..its all of it.
