06 F60TLR possible vapor lock ???

[rodbolt17]

like I said.
if by pumping the primer to refill the gas tank keeps it running you don't have a problem in the gas tank.
gas tank being the VST.
your issue is between the gas tank and the liquid in the hull gas tank.

your boat has two gas tanks at least.
one or more in the hull and one on the engine.

[Fred Pittman]

Yes, Rodbolt. I do understand that. What I don't understand is WHY it is happening in the first place. I haven't eliminated vapor lock though. It's my understanding that the fuel cooler only cools the excess fuel that the pressure regulator sends back to the vst so at low rpm's , most of the fuel is recirculating back into the vst and being supposedly cooled. So, in a vapor lock situation, would boosting the pressure in the line between the lift pump and the vst possibly overcome this situation momentarily?
My next trip to the water will be with another fuel tank and a different vst.
The only thing I can think at the time is possibly a sticking needle in the vst causing it not to refill and pumping the fuel pressure up to between 10 and 20 lbs. maybe "unseats" the needle allowing fuel into vst.

[fairdeal]

It's my understanding that the fuel cooler only cools the excess fuel that the pressure regulator sends back to the vst so at low rpm's , most of the fuel is recirculating back into the vst and being supposedly cooled. So, in a vapor lock situation, would boosting the pressure in the line between the lift pump and the vst possibly overcome this situation momentarily?

That "cooling" seems me, also, to be on a "relative" basis...since the "cooling" water has already passed around the oil pan and at least some of the hot engine /exhaust stack castings. (And in my area, may have already been >90 F before it ever entered the LU)

Perhaps I'm wrong, but my definition of "vapor lock" occurs on the "suction" side of a pump; it simply doesn't exist where gas is "under pressure"

The only thing I can think at the time is possibly a sticking needle in the vst causing it not to refill and pumping the fuel pressure up to between 10 and 20 lbs. maybe "unseats" the needle allowing fuel into vst.

I like the theory. Although IIRC - way back at the beginning of the thread -
didn't you try an "auxiliary" electric "lift pump" - to no effect?

[Fred Pittman]

Yes, but the pump I used only put out max pressure of 2 1/2 to 3 lb/in., And this time I didn't have a primer to boost the pressure past 3 lb.. I had to wait a few minutes before motor would run again

[rodbolt17]

did you ever physically verify the fuel cooler can flow water ?

[99yam40]

Rodbolt, do you have an answer to how much pressure the lift pump should be running at?

[Fred Pittman]

Yes, Rodbolt. Fuel cooler is free and clear....

[Fred Pittman]

Will be pulling the vst back off this morning to switch the fuel pump over to the new (used) vst. I'll have the fuel cooler off and in hand to recheck it off the motor for any obstruction. I called the previous owner to ask if he'd ever had this problem with the motor but he said that he'd never *****ed with it or idled it any longer than it took to get past the no wake zones so it could be a problem that's always been there....

[99yam40]

could the cooler be open/clear but there be blockage somewhere else not allowing proper water flow?

Is there a good way to see how much water flow there is through the cooler while idling?

[pstephens46]

Runs straight thru cooler out the pilot hole, right?

[99yam40]

I do not know.
just was thinking if it used a side stream maybe.

I would think Yamaha would have used the tell tail stream as an indicator of blockage, but you never know

[pstephens46]

Had to go back 15 pages. Not sure on F60. Cooler right above tell tail on F150.

[Fred Pittman]

OK, I might be onto something here....While I had the vst off I traced the water plumbing to the fuel cooler. The back water hose on the fuel cooler runs from the cooler to 2 tees, the first tee is conneted to the onboard flush port, then it tees to the telltale, and then runs around the bottom of the lower cowling to the port side where it connects to the side of the block. The front cooler hose connects to an elbow where it runs under the lower starboard side of the block. I cannot blow air through the line (with my mouth on hose) on the starboard side. The port side however I can blow through easily. HMMMM !!!?
sec.4-3 of the manual says this is cooling water pilot hose (fuel joint to upper case) but it looks to me like it runs under the cylinder head to a fitting on the port side underneath the bottom spark plug. It's very tight down there and the elbow is pointing inward. The fitting is round and looks to be cast, not threaded so I cannot remove it. Any ideas guys? Should I be able to blow through that hose?????

[boscoe99]

OK, I might be onto something here....While I had the vst off I traced the water plumbing to the fuel cooler. The back water hose on the fuel cooler runs from the cooler to 2 tees, the first tee is conneted to the onboard flush port, then it tees to the telltale, and then runs around the bottom of the lower cowling to the port side where it connects to the side of the block. The front cooler hose connects to an elbow where it runs under the lower starboard side of the block. I cannot blow air through the line (with my mouth on hose) on the starboard side. The port side however I can blow through easily. HMMMM !!!?
sec.4-3 of the manual says this is cooling water pilot hose (fuel joint to upper case) but it looks to me like it runs under the cylinder head to a fitting on the port side underneath the bottom spark plug. It's very tight down there and the elbow is pointing inward. The fitting is round and looks to be cast, not threaded so I cannot remove it. Any ideas guys? Should I be able to blow through that hose?????

Looks to me like the hose should be free and clear from the block fitting to the mid-section fitting. Plug the tell tale outlet and then blow from either the block fitting to the mid-section fitting or vice versa.

When the motor is running how about performing a test and letting us know in which direction the water flows. From the block to the mid-section or from the mid-section to the block.

[99yam40]

while running on muffs maybe you can pinch off the different hoses with a pair of needle nose pliers to see if tell tail flow changes
or take them off one at a time to see what has flow and from what direction