40hp Johnson..... Hot or Not?

[Echoman]

I have a 1970 40 hp Johnson. I THINK it runs too hot. At idle, there is virtually no water exiting from the exhaust port and, after running it at high speed, and shutting it off, I can hear the metal "snapping". The paint around the cylinders isn't burned, but the motor runs sluggish at high speed. The small amount of water that exits is scalding hot and combined with steam..much hotter than other motors I've had.

I have replaced the impeller and the water pump gaskets. I cooked up the thermostat on the stove and it looked like it opened around 150F. Is there something I am missing that could be restricting the flow? Is there some technique for checking the flow?

 

[tashasdaddy]

Re: 40hp Johnson..... Hot or Not?

remove tstat and lower flush out, water passages on head could be clogged. the motor will get hotter right after it shuts down, do to no circulation. get an infrared thermostat.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93983

 

[crxess]

Re: 40hp Johnson..... Hot or Not?

^^^^^^^^........Follow above advice. Maybe a grommet got pinched on the water tube during re-assembly?

To reduce heat up on shut down allow idle for a few minutes after coming off plane before shutdown.

 

[Echoman]

Re: 40hp Johnson..... Hot or Not?

Thanks for the information. I never even thought of using an infrared thermometer and I've got one in my drawer!!

I'll try flushing the unit out and then check the grommet as sugested too.

The folks that participate in this forum are top notch professionals in my view !!!

 

[kenmyfam]

Re: 40hp Johnson..... Hot or Not?

Does sound like you have a restriction somewhere.