06 F60TLR possible vapor lock ???

[exeter27]

Here's hoping tomorrow yields some information that leads to a definitive answer. You've done a great job narrowing this down - and the culprit will show itself if you stick with it!

[Fred Pittman]

Man, I hope so.... Getting sick of worrying with this thing. I had an old "76" 20 hp Johnson 2 stroke that I *****ed with for years. Pulled the starter rope once in the morning, once after lunch. Idled all day nearly every summer weekend for years and NEVER stalled, not even once. Traded it for an air conditioner for my shop after the old pontoon boat was put to pasture. Sure wish I'd kept it.
That's why I bought the Yamaha 4 stroke. Read how dependable they were, and fuel efficient to boot. Read how much better the 4 strokes were for *****ing. I'm sure I'll love it if I can solve this little problem, but right now I'm 'bout ready to trade it for something....

[99yam40]

where did you read this?
4 strokes do not like running at low RPM for most of the time.
tend to make oil( contaminate the oil with fuel) if you do not run in upper RPM range to heat them up to help get rid of the fuel in the oil that happens at low RPM.
they are fuel efficient and quiet

[Fred Pittman]

OK guys, back on the water today. First 30 minutes eventful. Idling 700 to 900 RPM's, high pressure pump steady 40 lbs., lift pump pressure to VST 3 lbs., vacuum after primer bulb 1 HG. Stumbled and high pressure dropped to 10 LBs., then motor died.( lift pump was steady at 3 lbs.) Wouldn't start back up until I pumped the pressure up to 10 lbs. with the primer. Definitely fuel related. I stopped by the local Yam dealer on my way to the lake and his top tech came out and took a look at my setup. He told me to go ahead and run it and report back to him with the readings.
I stopped by on the way back and he seems to think it may be a voltage drop to the High pressure pump and told me to wire up a voltmeter pigtailed into the wires to the high pressure pump so I can monitor the voltage the pump is getting when it starts to stumble.
I had a 5 yr. old out with me today, so I didn't get to climb on back and drain and measure the fuel in the vst when it died. Will take back out next trip and do that before attempting to cut into my wiring harness. If the VST tank isn't full of fuel then there is no need to wire up a voltmeter. If the VST tank isn't full of fuel it seems to me that it's either vapor lock or a sticking needle/seat /float in the VST that's already been changed since this all started..... Fred

[fairdeal]

lbs.) Wouldn't start back up until I pumped the pressure up to 10 lbs. with the primer. .... If the VST tank isn't full of fuel then there is no need to wire up a voltmeter. If the VST tank isn't full of fuel it seems to me that it's either vapor lock or a sticking needle/seat /float in the VST that's already been changed since this all started..... Fred

As has been stated several times now - if pumping the primer bulb fixes it,

then you are not getting fuel into the VST under normal running conditions

[99yam40]

I guess the big question is is 3 psi from the lift pump the pressure it should be putting out?
seems kind of low to me, but I nothing about this motor

[rodbolt17]

DO NOT cut into the harness.
you can use paper clips slipped into the connector and tape.

try pumping the primer every few minutes and see if it stalls.

is your motor under any fuel pump bullitens?

voltage loss sounds a bit fishy.

[Fred Pittman]

Rodbolt, I really didn't plan to "cut" into the harness. Bad choice of words there. " Tap into" is what I should have said.
I read on another thread where it mentioned a "sight glass" to watch the level of fuel in the VST. Is this possible and can it be done safely? Like I add a clear tube to the drain hose of the VST and lift it up, secure it, and open the VST drain screw and vent the vst so the fuel level in VST would show on the sight tube as I idle along? I don't know if the VST remains under normal atmospheric pressure when engine is running or not. Just a thought....
The tech at the Yam shop ran my numbers and found no bulletins on the motor nor any recalls or anything, No warranty claims, nothing.... He wants me to replace the fuel filter in the VST and try it again, BUT that filter was CLEAN ! If it was clogged would it run from 2000 to WOT perfectly? Is there anywhere inside the VST that I could have missed cleaning ( some little passage that could be blocked with old ethanol junk) that I failed to clean out?

[Fred Pittman]

And yes, Rodbolt, If I'm in a position to catch the stumble in time I can pump the primer quickly and "save" it from dying.

[fairdeal]

I read on another thread where it mentioned a "sight glass" to watch the level of fuel in the VST. Is this possible and can it be done safely?
Like I add a clear tube to the drain hose of the VST and lift it up, secure it, and open the VST drain screw and vent the vst so the fuel level in VST would show on the sight tube as I idle along?
I don't know if the VST remains under normal atmospheric pressure when engine is running or not. Just a thought....

I believe Boscoe floated the clever idea of a VST sight glass.

I "have a sense" that the headspace of the VST varies vs. atmospheric pressure -
but I think it would be "safe" - and work well -
if you Tee the top of your "sight glass tube" into the existing VST vent tubing.

Looks like your VST already has a "hose barb" on the VST drain;

any auto parts store sells inexpensive polymer "vacuum tees" one of which should be perfect for the vent tubing.

(You'll also need an appropriate piece of "splicer" tube when you are done)

[exeter27]

Good progress - at least you've narrowed it down to a small 'fault domain'. I don't know anything about the pump circuit (maybe someone has that), but is there a fuse involved? If so, perhaps it's got some corrosion? That's a long shot. But, monitoring the voltage can't hurt - and would rule out if it doesn't change.

Vapor locks are possible too, but it seems to inconsistent. Have you seen anything related to temp that would suggest it? All your reading suggest temps are staying normal...but to be honest, I didn't go back and re-read your prior posts on temp.

But, you fix the fuel delivery issue and you fix the problem. At least you know it's not ignition or compression related. It's suck, squeeze, bang, blow. You're having problem with bang - and we already know that ignition is good. Maybe I'm glad I have carbs on my F60 (2004)?!?!?!?!?!?

[99yam40]

can someone say one way or the other that 3 PSI on lift pump output is the correct pressure like he was reading?

if he has to pump the bulb up to where the pressure is 10 psi before it will allow motor to start and run again, the proper PSI of the lift pump output needs to be known


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

[exeter27]

Any updates Fred?

[Fred Pittman]

Didn't get a chance to do anything today. Not sure when I'll get back on the water. It's gonna be extremely difficult to drain and measure the fuel in the VST while on the water....I tried to get to the drain screw today in the yard while on the boat but found it nearly impossible to do. I did find another VST on Ebay with all hoses and fuel cooler still connected with a bad pump for $100 and free shipping so I ordered it. It should be here in a week.

[Fred Pittman]

OK, the used vst came in today. It's pretty clean but I used some spray carb cleaner on it anyway. The needle and seat/float seem to be functioning correctly so I'm gonna switch my high pressure pump into this vst. If it doesn't help I'll have a good clean vst for sale....I'm about running out of options here....