06 F60 TLR stalling at idle speed

[deltabull]

Motor runs fine past idle all the way up to 5500RPM, but when I try trolling at idle speed it will run for maybe 15 min., then sputter and die. If I pump primer bulb a few times it will run for a few minutes, then repeat. so far I have installed:
new high pressure electric pump (OEM)
new low pressure pump (OEM)
new fuel lines with primer bulb
new needle & seat and float inside VST
all new fuel filters
new water pump impeller
new fuel tank

this motor has only around 50 hrs. total run time on it. I thought I had the problem figured out last week but I was wrong. Bought new fuel hose and a Mr. Gasket #42s and wired it to my ignition switch for testing. Took it out and after about 15 minutes of trolling at 700 RPMs it sputtered and died. This time I had no primer bulb to pump it back up. After maybe 10 minutes or so it cranked back up so I ran back to ramp at 1/2 throttle and loaded up. I'm beginning to think vapor lock... any suggestions?

 

[99yam40]

have you tested anything?
or are you just throwing parts at it?

VST is suppose to be filled with fuel and eliminate any vapor, so not sure how it can be vapor lock

 

[deltabull]

Thanks so much for the reply, 99yam40. This problem has been going on since I got the motor over a year and a half.ago.. All these parts were done over that time period, one at a time trying to eliminate the problem. As far as testing, each time I take it out is a test. I'm not a boat mechanic but do have some knowledge of mechanics . I'm an ASE certified auto parts man, 63 years old, and on a very limited budget. My local Yammy shop is far too rich for my income level. It's gotten to the point ( with the wifey) that if I can't fix this thing soon, I'm gonna have to sell it at a loss and not own a boat. Just hoping some good Samaritan here can help walk me through some testing procedures so I can enjoy my boat and not keep throwing money at it that we don't have. My plan today (my day off) is to go find a barrel to run it in ( not gonna use cuffs this time), let it idle in gear until it dies, then drain the vst and measure how much fuel the vst tank has in it. Also will be taking temp readings at various points on the motor as it runs. Also, gonna remove the thermostat and crank it cold with the cover off and see is I have sufficient water flow at idle...(will only run it for a few seconds that way) Do you have any other suggestions as to which direction I should look? ( note- I also removed the electric fuel pump and put my primer bulb back on)

 

[deltabull]

I have good water flow at thermostat housing at idle with thermostat out. I tested thermostat in pan of water on stove. Full open at 150 degrees. Tried to check water temp thermocouple by dropping into boiling water with ignition on and got no buzzer. Tested harness side of thermocouple plug with test light. Got no voltage on either wire, again with ignition on. Does motor have to be running to get power there?

 

[99yam40]

being I have little experience with 4 strokes I do not have much help.
But I would measure fuel pressures into and out of the VST to see what is going on when it runs and dies.
there may be a check valve/recirculation valve maybe that could stick. I do not know
might even tee in a vacuum gauge on the input to lift pumps to see what was going on that side of the fuel system also.
maybe there is too much vacuum building up for the low Pressure pump to over come after running for awhile.

hooking up a clear hose after the lift pumps (for testing only) should show if you are sucking air into the system. Maybe it is sucking air and the pump is not moving enough fuel to keep the VST filled up when at low RPMS
does the low pressure pump run off of 12 volts or is it mechanical?

You would probably get more help from another forum.

do a web search for Rodbol17 and post there

 

[deltabull]

Thanks so much for the response. . I have gotten a response from Rodbolt17 on another forum. Have a great day !

 

[99yam40]

as far as the overheat on those 4 strokes I have read that it is not as simple to test like the 2 strokes.
resistors, jumpers, RPM threshold, along with timespan needed to get alarm to sound off