06 F60TLR possible vapor lock ???

[Fred Pittman]

I don't want to write a book here but I desperately need some expert help. 2006 F60TLR with around 50 hrs on motor. Bought the motor for pontoon boat mainly to be used for *****ing and it's been driving me crazy. Motor cranks and runs great until I drop it down to idle speed. I start to ***** and everything's fine for 15 to 20 minutes, then it starts to sputter, rpm's drop to around 300, then it dies. This problem has been happening ever since I've had the motor. ( Note: It was used in brackish water by previous owner) It won't immediately restart, engine fires up immediately, runs a few seconds and then dies. After a few minutes it will start and run fine for a few minutes if idling, if I speed it up it runs great.
What I've done so far: new high pressure pump, new needle, seat, float in vst, new fuel filters, new fuel hose with new primer bulb, new fuel tank, new low pressure (lift) pump and new water pump kit.
I have noticed that when it starts to sputter I can squeeze the primer bulb a few times and motor catches up, smooths out and idles good for a few minutes, then repeats....This led me to think air leak in fuel line but now I have ruled that out. This week I bought new fuel hose and a Mr. Gasket electric fuel pump 2 1/2 to 3 PSI and installed it for testing purposes. I wired it to the IGN. switch and headed to the lake. Idled great for about 30 minutes then sputtered and died. Electric pump humming away, no primer bulb to squeeze to keep it running this time. I removed the engine cowling and removed the clear fuel bowl, looking for anything at this point. No water in bowl or trash. I put bowl back on , turned IGN on and watched the bowl fill up. Turned the key and it fired right up. I didn't try to idle anymore, just opened her up and headed for the boat ramp.
I did notice when leaning over fooling with the filter bowl that the back of the motor felt hot. I placed my hand on the back of the head by the oil fill plug and can hold my hand there for 4 to 5 seconds only. Then I felt VST box with my finger and it was hot too.
I just removed the electric pump and put the primer bulb back inline. I removed the kill lanyard and turned the IGN on and beeper is working, but no beep when on the water at all which should tell me that motor isn't overheating. I'm really stumped on this... Can anyone please help????? THanks in advance, Fred

[rodbolt17]

make sure your fuel pump can actually pump at low speeds.
make sure the fuel cooler is clear.

[Fred Pittman]

Is the fuel cooler located just to the rear of the VST tank? Also just read 80 pages of topics here ... Found one about testing temp sender by unplugging pink wire and grounding harness side to test warning beeper. There is a pink/white stripe wire right behind starter solenoid. I tried but got no beeper. Then I looked just in front of thermostat cover and see a probe there with double wires in black jacket. Seems like this should be the temp probe. Which one do I test for temp alarm not functioning? Thanks, Fred

[Fred Pittman]

OK, I found parts pic and the pink/white wire is to oil pressure switch. How do I test the temp thermocouple?

[rodbolt17]

to test the thermocouple you have to short the switch wire and use a resistor acrossed the sensor wires.

some late model stuff only uses the ECT, on those you have to figure out what the resistance is at about 212*F and go a bit lower with a resister across the connector then there is a time and RPM delay.

[Fred Pittman]

ok, so far today I removed the thermostat and ran in barrel for a few seconds with housing cover off. Got good water flow at idle.... Tested thermostat in boiler on stove...full open at 150 degrees. I removed the temp warning sensor and tried dipping it into 212 degree water for 1 minute with ignition on and got no warning buzzer. Then I used a test light and checked both wires at the harness plug for voltage. I got no light. I removed the hose at the bottom of the fuel cooler and blew through it. Seems open with no restrictions. My next step is to run in barrel and take temps with infrared gun. Also, if I can get it to stumble and die in the barrel I will drain the VST and measure the amount of fuel there. Thanks for the help, Fred

[Fred Pittman]

OK, I bought infrared thermometer, started motor in barrel and let it idle. Everything was going good for about 5 minutes. I watched the temp at thermostat housing climb from 100 to 149 then it opened and temp immediately dropped down and averaged about 123. Fuel cooler temp about 106.Motor peeing lukewarm water, good steady stream. As it was running I noticed the telltale stream was slowing down somewhat so I held my hand in the water and it was getting HOT...About that time the temp alarm buzzer went off and temp at thermostat housing was up to 200. I immediately shut it down. First time I have ever heard the temp buzzer....

[99yam40]

at least now you know it works, so you do not have to rig up something to test it

still need to be checking fuel pressures to see what they are doing.

But I have no idea why it overheated, has it ever done that on the muffs?

Have you noticed tell tail dropping off while on the water?

[pstephens46]

Seems like we started with a running issue with no temp alarms to now overheating with no running issues in the barrel?

[Fred Pittman]

I can't understand about the temp alarm unless somehow I wasn't getting a good connection to the harness until I disconnected it, the reconnected it. I didn't let it run long enough to stumble and die after the temp alarm sounded. I just checked the water pump and it looks good. Thinking about trying it without the thermostat in to see if it heats up..... We need a smilie icon here of a headscratcher...lol

[Fred Pittman]

Never ran it that long on muffs

[pstephens46]

you said you ran in barrel? I take that to mean lower unit was in a tank drawing water normally. Or was it on muffs? My F150 will not get enough water on muffs so I hook up two hoses, muffs and other to flush connection. Works great that way, Provided yours has a flush connector? May have overheated due to not getting enough with muffs.

[pstephens46]

Bought one of those brass Y connectors for the faucet to make it easier to use two hoses.....

[Fred Pittman]

OK, latest update: took lower unit off, checked water pump, backflushed from thermostat housing down thru pickup tube. I put lower unit back on, left thermostat out and idled on muffs for 30 minutes....motor stayed cool, telltale stream very weak, cold water from telltake, hot water from exhaust/hub. Cyl. head temp never exceeded 125. I then cut it off, reinstalled same thermostat and ran on muffs for about ten minutes. Telltale much stronger. This time thermostat opened at 130, stabilized at 123..... Motor never tried to stumble and die. Just wish I had something definite to blame for it. Probably a sticking thermostat......

[99yam40]

replace it, cheap enough.
, but it still sounds like a fuel delivery problem from what you have said