Smokes when held at full throttle

K

kramer588

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Aug 9, 2011
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I have a mid 70s Johnson 25hp tiller, the motor runs fine at half throttle but when held at full throttle for a minutes or so it starts smokes a lot and loses power. I throttle back and let it cool down and it runs fine again when at half throttle. Any advice would be great!
 
K

kramer588

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Re: Smokes when held at full throttle

Could this be steam coming out of the exhaust? like if water would be getting in somewhere it shouldn't be
 
soundchaser

soundchaser

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Dec 8, 2009
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Re: Smokes when held at full throttle

sounds like it's not getting too much water at all and overheating.
 
Borgey401

Borgey401

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Jun 11, 2011
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Re: Smokes when held at full throttle

kramer588 said:
I have a mid 70s Johnson 25hp tiller, the motor runs fine at half throttle but when held at full throttle for a minutes or so it starts smokes a lot and loses power. I throttle back and let it cool down and it runs fine again when at half throttle. Any advice would be great!
Click to expand...
I would check the impeller out to see how good of shape it's in. How's the telltale look when you're WOT?
 
K

kramer588

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Re: Smokes when held at full throttle

Borgey401 said:
I would check the impeller out to see how good of shape it's in. How's the telltale look when you're WOT?
Click to expand...
I'm new to the site and not sure what you mean by the telltale and also not sure what WOT stands for
 
scipper77

scipper77

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Re: Smokes when held at full throttle

WOT = wide open throttle.

The telltale is a stream of water that comes out of the lower unit above the water line. Sometimes called a pew stream it indicates that water is being pumped through the cooling system by the impeller. If there is no stream there OS no cooling. If the stream is weak you may only see an overheat at idle or WOT.
 
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kramer588

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Aug 9, 2011
Messages
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Re: Smokes when held at full throttle

The telltale is not a steady stream but more of a spray, it is however a constant flow. The motor is old and i'm sure the impeller is also very old, it does seem like it is overheating at WOT, so im thinking a new impeller should do the trick
 
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