telltale water super hot on 4HP yamaha 1990 2 stroke

doranjames

Recruit
Joined
May 7, 2010
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i have a 4SD Yamaha OB - bought from an old guy that i am sure took great care of it - motor starts easily and runs but tell tale water starts to steam and gets to hot to touch (then i shut it down)

i have dropped the lower unit and changed an impeller (was in need of change but not terrible shape)

i have done tricks like running in bucket with super hot water with a little CLR mixed in

the telltale stream is pretty weak (not strong and very very weak at idle)

i am guessing that it could be the thermostat

QUESTION - looks pretty simple to unbolt the exhaust plates and get to the thermostat - do these usually fail? do the exhaust bolts need to be precisely torqued (with torque wrench) when reinstalling will exhaust gaskets survive tear down or should i order with thermostat

if anyone has worked on these smaller OBs and can send some advice i would be appreciative - i am a bit mechanical but no wrench whizz
 
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