Yamaha 140Hp Overheating

[Rapson]

Re: Yamaha 140Hp Overheating

Yeah the key is in, it would be a right mongrel to put together if it wasnt. Going to try to get some new poppit valves this week and try them, have read a few others have had the same problem and turned out to be the poppit valves. Thansk for your input SparkieBoat.

 

[99yam40]

Re: Yamaha 140Hp Overheating

Make sure the impeller is turned in the right direction when installed.
Is it possible you have an exhaust leak down around the water pump due to corrosion or malformed rubber dampener.

 

[Rapson]

Re: Yamaha 140Hp Overheating

Make sure the impeller is turned in the right direction when installed.

How can I tell which way the impeller is meant to be? There is nothing in the manual I have about this.

 

[99yam40]

Re: Yamaha 140Hp Overheating

pay attention to the direction the motor turns when running and make sure you turn the shaft the same direction that the motor would turn it , and make sure the impeller is turned in the direction that the vanes follow the center section

 

[SparkieBoat]

Re: Yamaha 140Hp Overheating

you may have really hit on something here 99...as far as I know all the motors turn clock wise looking down the drive shaft from top. (with only a few rare exceptions..but not sure about non US motors) you should spin drive shaft in this direction as you slide the water pump housing over the impeller..check your impeller for damaged fins.

 

[Rapson]

Re: Yamaha 140Hp Overheating

Dismantled the water pump and checked it before the last trip and it still looked like new. I have ordered new poppet valves and should be here by Friday I am hoping, it they dont fix the problem I shall take the pump apart again and check that it is going the right way.

 

[99yam40]

Re: Yamaha 140Hp Overheating

Is it possible you have an exhaust leak down around the water pump due to corrosion or malformed rubber dampener.

Make sure it is not sucking air or exhaust into the water pump

 

[Rapson]

Re: Yamaha 140Hp Overheating

Quick update to this ongoing saga. I installed 2 brand new poppet valves, the new mushroom type ones, and she is still over heating. When I got up to speed at about 4000rpm a mate had a good look at the motor and saw water spraying out from where the lower case connects to the leg, where it shouldnt be comming from! I am asuming there is a leak somewhere above the water pump, busted seal or even a coroded pipe but atleast I have found a problem!

 

[SparkieBoat]

Re: Yamaha 140Hp Overheating

yes..sounds like you have a leak in your water pump or where the tube connects to water pump..there is a seal that goes there I think..have you checked for a split in the tube?? What makes me suspect the pump is you said you get great pee stream when you connected a hose to the tube, but no where near as strong with the pump. This makes me think everything from the tube up is ok. check bottom of tube also for dent/damage and top of water pump..also is it possible the water tube got bent or something?? maybe causing it to go into pump crooked?? hook your hose back up to the tube and check for tube damage...check impeller for the fins to be turned in the right direction and also do a close inspection of water pump housing and all seals. your problem has to be in there somewhere.

 

[Rapson]

Re: Yamaha 140Hp Overheating

Checked pump and the vanes are going in the right direction. Stuck the hose on the pump and on the water pipe and all good, water going where it should and not where it shouldnt. The water that was coming out of the leg when at speed is at the rear of the leg and has already passed through the engine. I am now thinking it is the chip on the side of the cylinder liner and a blockage that I can not see. I think I am resigned to the fact that I will be going slow until I can afford to upgrade from this anchor which doesnt worry me to much as when I go out to sea I dont get the alarm triggered as the swell keeps our speed down. Thanks to all for your input, this thread has covered every known overheating issue known to man and hopefully will provide a resource for others.