Yamaha 140Hp Overheating

[SparkieBoat]

Re: Yamaha 140Hp Overheating

I think that engine could keep working for a long time. i am not sure what you are talking about though with the cylinder wall, maybe a pic would help. When it is over heating were both heads over heating or just one?? you can use the 3 second touch rule, if you can hold your hand on the top of the head for 3 secs it is not over heated. figure which head is over heating then focus there. I do not think it is the cylinder wall, unless it is allowing cylinder pressure to escape, that would be bad. again if you can take a pic and post it, that would be helpful

 

[99yam40]

Re: Yamaha 140Hp Overheating

A previous owner removed the oil pump etc so I pre mix my fuel. After removing the heads I thnk my problem is a small piece that has corroded off the side off the cylinder wall, which happens to be right where the temp sensor is. Could possibly try toge *** welded but I have concerns that it could start a snowball effect with the remaining wall.

Can anyone recomend another fix such as a metal mend type product? I know it will be a temp fix but I dont expect to get to much more life from this engine.

I do not know of a fix for corroded passages that have eaten enough metal away that the flow is not following the proper path, esspecialy in the block and heads.
Seems like I remember a post where some one having a corrosion problem below the water pump that allowed air to be sucked into the water pump that was fixed with JB weld or something like that, but it may have been on a suzuki not a Yamaha

 

[Rapson]

Re: Yamaha 140Hp Overheating

 

[SparkieBoat]

Re: Yamaha 140Hp Overheating

that is a pretty good nick there...but I bet you could get it to seal with a new head gasket, it does not look like it was losing compression through the old gasket. I think your over heat problem is something else. if anything it looks like you had a blow out at the bottom of the top cylinder..see that black mark there. clean it all up good and new head gasket...see what happens. were both heads over heating or just one??

 

[Big flop]

Re: Yamaha 140Hp Overheating

I'm with sparkieboat, it looks like it will clean up. Bottom of top cyl looks
Suspicious or is that oil? Is the bottom spark plug packed with rusty crud?

 

[Rapson]

Re: Yamaha 140Hp Overheating

Thanks for the input guys. I have cleaned up the heads, pics attached. I dont know if I should attempt to get the chip welded or not, got a feeling the head liner might start falling apart. I am considering just putting it back together, got a new head gasket and will get some new plugs to.

 

[douglasesanford]

Re: Yamaha 140Hp Overheating

there is a poppet or pressure valve on the bottom of the exhaust cover with a hose going to the engine holder. The valve will stick to the grommet due to corrosion getting between the gormmet and block. Pull 2 10 mm bolts out and the spring and see if you can twist or pull it out. clean corrosion out and test- good luck

 

[Rapson]

Re: Yamaha 140Hp Overheating

Thanks Douglasesanford, I will see if I can find it and give it a good clean out. Cheers!

 

[Rapson]

Re: Yamaha 140Hp Overheating

Doug, I have found that the valve you are speaking of are located there on the V6's (150hp and above) My 140 is a V4 and the valve is located just under the Thermostat and under the same cover. I have given them a good clean and they look ok but I might try and get some new ones anyway.

 

[Shivam]

Re: Yamaha 140Hp Overheating

hey good stuff rapson!!!

 

[Rapson]

Re: Yamaha 140Hp Overheating

Update on the overheating issue.
Todate I have replaced the water pump (new housing, impeller, seals the works), new thermostats, taken off water jackets and cleaned, taken off heads and cleaned and replaced with new head gaskets, tested thermo switch (both trigger at 85c) and tested the warning buzzer circut by the book (get engine to over 2500rpm, disconnect thermo switches and connect the wires, buzzer sounds, engine drops to below 2000rpm, disconnect thermo switch wires and buzzer goes off.
After all that I go out the other day, cruising at just over 4000rpm and the buzzer goes off. I pull off the cowling and find that I can comfortably put my hand on the heads for atleast 5 seconds with out being burnt.

Can anyone shed some light on this or do I have a new anchor?

 

[SparkieBoat]

Re: Yamaha 140Hp Overheating

does not sound like motor is over heating to me..sounds like a sensor/wiring issue..5 secs is about right.

 

[99yam40]

Re: Yamaha 140Hp Overheating

how tough are your hands?
It would be better to shoot the heads with a temp gun so everyone knows what temp you are talking about

 

[Rapson]

Re: Yamaha 140Hp Overheating

I have soft hands and it was about the same temp as at idle.

I have tested the sensors by the manual are there any other ways of testing it. Might have to get a temp gun i think

 

[99yam40]

Re: Yamaha 140Hp Overheating

Are you sure it is the overheat alarm or could it be the low oil level alarm going off?

 

[SparkieBoat]

Re: Yamaha 140Hp Overheating

a temp gun would be a good idea just to make sure, but I have put my hand on a hot head before and it burns quick about 1 second all I can stand. you defiantly need to trouble shoot your wiring/alarm

 

[Rapson]

Re: Yamaha 140Hp Overheating

I have done a full test of all the circuts and they are all good. I an now convinced that the engine is in fact over heating as it fails the 3 second rule now and both cylinders send off the thermo switches. Had a good run with a mate yesterday and we were not happy with the amount of water comming out of the tell tale when at speed. As this water has not yet passed through the heads I am now leaning towards the water pump, if there was a blockage in the head the tell tale would have heaps of pressure. I have replaced the whole pump, impeller, housing, plates and dispamtled and checked and all looks fine. Recently had the gear shifter bracket break and had to take the power head off to replace it and replaced the gasket at the same time and all looked good from there.

This motor is starting to look like my grandfathers knife, the one with the new handle and the new blade.

 

[SparkieBoat]

Re: Yamaha 140Hp Overheating

maybe a clog in the water tube going from pump to head...

 

[Rapson]

Re: Yamaha 140Hp Overheating

I have taken the lower leg off and put the hose on the inlet and get full pressure from the tell tale.

 

[SparkieBoat]

Re: Yamaha 140Hp Overheating

sounds like a problem with the pump...maybe impeller slipping///or maybe wrong size impeller///or some other odd thing happening there///the key is in isnt it???