Yamaha 40 HP C40TLRV OUTBOARD OVERHEATING

[tcarpe1]

I HAVE WATER COMING OUT OF PEE HOLE, I ALSO HAVE WATER COMING UP TO TSTAT (took tstat out and tested for water coming up).

WHAT WOULD CAUSE THE ENGINE TO GET HOT?

WATER COMING OUT OF PEE HOLE IS WARM LIKE A HOT TUB.

 

[99yam40]

plugged cooling passages, cracked head, water pump not pumping enough water, bad stat

 

[tcarpe1]

Took tstat out and had cover off and water was coming out pretty good. spayed water through pee hole and it came out the bottom, is there another cooling passage that I need to investigate?

cracked head don't sound good......

 

[tcarpe1]

For the cracked head, I am assuming I need to do a compression test?

 

[99yam40]

when was the water pump replaced last?
do you know if stat opens and closes to spec?

lots of cooling passages in motor that need to be open for proper water flow for proper cooling of head and block

 

[tcarpe1]

I changed water pump this year. I ordered a stat and will give it a try

 

[mjf55]

Try running without thermostats installed. Does it overheat then?

 

[robert graham]

Do you have good strong water pressure from your hose feeding your flushing muffs?.....weak water flow at muffs can cause overheating....ask me how I know!....

 

[tcarpe1]

I wondered that about the muffs. Gonna try it in a barrel and without thermostat.

 

[tcarpe1]

I ran without thermostat and it did not overheat. The water coming out got hot for about a minute, but was just warm most of the time.

2 mins warm, 1 min hot, 6 mins warm. What could be the reason for that period of hotness? overall I was pleased with the result. A lot better than what it has been.

 

[99yam40]

test the stat in a pot of water while heating it with a thermometer measuring the temp to see if stat is opening and closing in spec.

running a water cooled motor with the stat out will cause cold and hot spots in areas of motor do to water not being forced to circulate properly

 

[tcarpe1]

Thanks. Makes sense. I have a new stat I will check before I put it in.

 

[lilbubba]

I have a 70 yam. that was overheating at above mid throttle . Wound up pulling head and water jacket was plugged . This was with less than 250 hours . Just not enough flow going thru to keep from having build up . Checked thermostat 2 years later with no more than 100 hours and its mostly plugged again . Been running without thermostat and doing just fine . The pee hole on mine seems to be just an indicator the pump is pumping . Water thru head comes from an appx. 5/16 hole in head gasket which doesn't allow enough water flow to keep things from building up....The only flaw I see in yammy 3 cylinders....

 

[tcarpe1]

I may be having similar issue. I changed thermostat and found pieces of rubber. I'm having starting issues right not so I have not been able to run it to test the water flow.