Stalling after x length of run time
Posted: July 25th, 2021, 5:34 pm
I had an odd thing happen yesterday and I could use some help troubleshooting it.
We took a 5 hour run north on the Mississippi last Monday. Speed was a constant 8mph roughly 1800 rpm. Ran the generator the entire trip. Arrived at the marina after about 5 hours with no issues or drama.
Yesterday we did the same run back down to our home marina after spending the week as transients. We topped off the port gas tank with 7 gallons of gas to balance the tanks since the generator runs off the port tank.
We pretty much idled through a no wake for the first 20 minutes, then popped up to 2100 rpm and took off down the river. Got about ten minutes into the run and the port motor died. Did some checks on it and things looked ok, not hot, oil pressure good, voltage good.
Fired it back up, sounded perfect. Throttled up to 1900 rpm and made it another half hour and it did the same thing.
The generator never shut off during all of this. Someone then suggested shutting that down in case it was drawing a lot of fuel from that tank.
Long story short, we would run about 45 minutes and then lose the port motor. Did that the entire ride back. I could start it almost instantly after it died. No cooling off required. I also took an ir gun into the engine compartment to see if anything was hot. Temps on the two fuel pumps were 97 and 101. Not hot. Risers were 114.
1995 355 Aft
Twin 454 xli Crusaders. Throttle body injected.
My first thought was vapor lock. The motor would die similar to when you pull the fuel line on a lawn mower to winterize it. It would slowly ramp down, not shut off instantly.
I ran the rest of the trip with the port gas cap off, which didn’t help.
I’m thinking maybe anti-siphon valve? Does that sound right?
Fwiw both of my motors have had their main fuel pumps replaced in the last two years. I have not replaced the little helper pump on either motor.
Fuel filters and water separators were also replaced this spring.
If it is the anti siphon valve, where is that on top of the tank? Is it easy to get to? Is it going to be stuck on there and a pita to remove? I can’t get down there until next Sunday so I want to be prepared for what i need to do for this project.
Is there anything else I can look for that would cause similar symptoms? I do plan to look at the fuel lines to see if any are soft and need replacing.
I have yet to use my aux tank. The PO claimed it was fine. I could fill that and run off that tank to see if it solves the problem. A little nervous to use it since I haven’t yet. Don’t want to find 25 gallons of gas in my swim platform!
Thanks for any help an advice
We took a 5 hour run north on the Mississippi last Monday. Speed was a constant 8mph roughly 1800 rpm. Ran the generator the entire trip. Arrived at the marina after about 5 hours with no issues or drama.
Yesterday we did the same run back down to our home marina after spending the week as transients. We topped off the port gas tank with 7 gallons of gas to balance the tanks since the generator runs off the port tank.
We pretty much idled through a no wake for the first 20 minutes, then popped up to 2100 rpm and took off down the river. Got about ten minutes into the run and the port motor died. Did some checks on it and things looked ok, not hot, oil pressure good, voltage good.
Fired it back up, sounded perfect. Throttled up to 1900 rpm and made it another half hour and it did the same thing.
The generator never shut off during all of this. Someone then suggested shutting that down in case it was drawing a lot of fuel from that tank.
Long story short, we would run about 45 minutes and then lose the port motor. Did that the entire ride back. I could start it almost instantly after it died. No cooling off required. I also took an ir gun into the engine compartment to see if anything was hot. Temps on the two fuel pumps were 97 and 101. Not hot. Risers were 114.
1995 355 Aft
Twin 454 xli Crusaders. Throttle body injected.
My first thought was vapor lock. The motor would die similar to when you pull the fuel line on a lawn mower to winterize it. It would slowly ramp down, not shut off instantly.
I ran the rest of the trip with the port gas cap off, which didn’t help.
I’m thinking maybe anti-siphon valve? Does that sound right?
Fwiw both of my motors have had their main fuel pumps replaced in the last two years. I have not replaced the little helper pump on either motor.
Fuel filters and water separators were also replaced this spring.
If it is the anti siphon valve, where is that on top of the tank? Is it easy to get to? Is it going to be stuck on there and a pita to remove? I can’t get down there until next Sunday so I want to be prepared for what i need to do for this project.
Is there anything else I can look for that would cause similar symptoms? I do plan to look at the fuel lines to see if any are soft and need replacing.
I have yet to use my aux tank. The PO claimed it was fine. I could fill that and run off that tank to see if it solves the problem. A little nervous to use it since I haven’t yet. Don’t want to find 25 gallons of gas in my swim platform!
Thanks for any help an advice