150hp overheating at high rpms

[fisherman11648]

1998 yamaha 150hp txrw.it overheats at 4000 rpm let cool for a very short time then all is ok,as long as i dont go above 3500rpms. but it seem to be starting to over heat at lower rpms. like at 3800.Have plenty of water comming out of outlet. pressure is good. waterpump was changed last May 2004. Could this be a problem with a popet valve? If so where is it located?

 

[fisherman11648]

Re: 150hp overheating at high rpms

also put new thermos. in just 4 weeks ago..

 

[Ray Neudecker]

Re: 150hp overheating at high rpms

The poppet valve is located at the back of the block low on the back plate. Looks like a thermostat housing.

 

[rodbolt]

Re: 150hp overheating at high rpms

usually high speed cooling issues are not poppit valve related, never see it on a yam. most likly its head gasket or cover related.<br /> its common to see low speed poppit issues. saltwater is great stuff

 

[fisherman11648]

Re: 150hp overheating at high rpms

rodbolt: plz explain cover related problem.Should i not mess with with poppit valve.. Maybe just change Head gaskets.They are easy to change.I just need to know how much to torque the bolts.Anyone know?. This boat gets used a great deal. Ray what do you think.? Yes Salt water is tough..

 

[fisherman11648]

Re: 150hp overheating at high rpms

Also should I go ahead and replace the poppit valve?

 

[rodbolt]

Re: 150hp overheating at high rpms

poppit valve replacement is part of regular maint. on a well maitained boat you most likely will never need a pump a t-stat or valve grommet. however the heads, cyl passages and water covers on the heads will scale up with salt and need to be manually cleaned, buy a service manual and ask service related questions

 

[bigbrownbuku]

Re: 150hp overheating at high rpms

the poppet is easy to check, its just 2 6mm bolts low on the right side of the exhaust plate or "cover" between the heads. when was the last time you had your water pump serviced? its a quick job to re and re the gearbox to check the waterpump before you start in on the heads.

 

[Ray Neudecker]

Re: 150hp overheating at high rpms

I would service the poppet valve. That should be a regular maintence item. I do agree with Rodbolt that the main problem will be elsewhere. Fortunately, we don't have to deal with salt except on the table,but the bass fisherman around here sub in pea gravel to stop up heads and restrict water passages.

 

[fisherman11648]

Re: 150hp overheating at high rpms

Thanks each of you for all the info.. The professional will be checking it out Tuesday at my house. I'll watch him and then next time Its my job... .. Thanks again .. Come down & I'll take you fishing.. Really

 

[fisherman11648]

Re: 150hp overheating at high rpms

Rodbolt you're 100% correct.. real trouble was under the covers pretty gunked up but no major problems.. having them beaded and cleaned.. took heads off and cleaned the passages.. Not that bad for never being done before. And it not a tough job at all.. All the bolts came out just fine.. Will be fishing for Snook on Sat. Thanks again.