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Old 19 August 2006, 15:04   #1
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Tohatsu 50 Thermostat

Hi
Supplimentary question to my existing post about running on 2cyl...

How can I tell if the engine is getting up to temperature (cool engine could be why plugs are fouling)? From some other threads it looks like the idle port below the cowling (not tell tale which is on all the time) only has water coming out of it once the thermostat has opened. Does this mean the water coming out of this should be at 50-60C? - I can't remember if I normally have water coming out of here or not - will check next time I'm down at the boat.

I'm assuming that there are effectively 2 water circuits on the engine. One thermostatically controlled only allowing hot water out (therefore cold water in) to the loop around the cylinders. There then also must be a secondary loop bypassing the cylinder taking raw water and outputting it to tell-tale and exhaust (otherwise huge pressures would build up with pump impeller). Is this correct?

So, where does the water from the cylinder cooling loop go - straight into exhaust or out of the idle (or some other) port.

I can't find a service manual for 06 engine (2000 is the latest clymer one I can source).

Thanks,
Al.
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Old 21 August 2006, 14:55   #2
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Does anyone even have an older shop manual that shows cooling cct of older tohatsu 50's? I guess they haven't changed that much!

Thanks,
Al
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Old 21 August 2006, 15:35   #3
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hmmm, like to help !! im pondering!
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Old 21 August 2006, 15:41   #4
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Quote:
Originally Posted by al40

So, where does the water from the cylinder cooling loop go - straight into exhaust or out of the idle (or some other) port.

I think, as far as I can tell, the water from the cooling loop comes out of the grills on each side just above the ventilation plate. Your description of the cooling system I think is right. My thermostat has 60deg stamped on it, but the engine should run fine (although may use a little more fuel) even if you take the whole thermostat out, which leads me to think you shouldn't really ever have a problem with an engine running too cool, only too hot.
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Old 21 August 2006, 19:15   #5
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Quote:
Originally Posted by slimtim
I think, as far as I can tell, the water from the cooling loop comes out of the grills on each side just above the ventilation plate. Your description of the cooling system I think is right. My thermostat has 60deg stamped on it, but the engine should run fine (although may use a little more fuel) even if you take the whole thermostat out, which leads me to think you shouldn't really ever have a problem with an engine running too cool, only too hot.
That description matches what my engine does, on a hose an mufss the motor will hit 60deg pretty quick.
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Old 22 August 2006, 11:22   #6
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thanks. I'll give it a try with muffs and measure output water temp.
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Old 22 August 2006, 14:45   #7
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Quote:
Originally Posted by slimtim
I think, as far as I can tell, the water from the cooling loop comes out of the grills on each side just above the ventilation plate. Your description of the cooling system I think is right. My thermostat has 60deg stamped on it, but the engine should run fine (although may use a little more fuel) even if you take the whole thermostat out, which leads me to think you shouldn't really ever have a problem with an engine running too cool, only too hot.
It's possible that the engine is oiling up because it's running too cool (see other post re running on 2cyl). I need to take a really good look at it but I think it may be the bottom cylinder that's playing up which would makes sense as it will be the 1st in line for cooling. If stat is jammed open, then that cylinder will get more cooling than the others. Of course this is all supposition at the moment until I've actually gone down to the boat and looked :-) Thanks
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