engine stalling

[lcraig]

Just repowered with used 2005 df140s. Both engines idle fine but port motor loses rpm after a couple of minutes over 2000 rpm. If I leave the motor in gear, it will drop and go back up. Sometimes it will stay up for a little while and sometimes it will just drop back down. If it goes back up, it will go back down. Starboard works like a champ. I have changed low pressure filter, high pressure filter, changed the fuel vapor separator and low pressure pump. I have also switched to portable tanks just in case it is something to do with the gas tank. Also changed fuel lines. What else is can caused this problem?

[artdf175]

it is sounding like it is starving for fuel, so I think you are working in the right direction

is the fuel tank vent working ? is the fuel bulb going flat when the engine starts to die

I think there have been previous comments about some anti siphon device on the fuel tank that some folks have removed because of problems like this

have you tried to run the engine with the fuel cap open enough so there are no restrictions for the fuel tank to vent?

and just double check all the fuel hose fittings to make sure there is no place air can get sucked into the fuel line
you might watch the small inline fuel filter, pre-low pressure pump with engine running and make sure there are no air bubbles being sucked into the system.
Art

[redlowrey]

Just repowered with used 2005 df140s. Both engines idle fine but port motor loses rpm after a couple of minutes over 2000 rpm. If I leave the motor in gear, it will drop and go back up. Sometimes it will stay up for a little while and sometimes it will just drop back down. If it goes back up, it will go back down. Starboard works like a champ. I have changed low pressure filter, high pressure filter, changed the fuel vapor separator and low pressure pump. I have also switched to portable tanks just in case it is something to do with the gas tank. Also changed fuel lines. What else is can caused this problem?

Sounds like a fuel problem, did you pull your vst down or replace it with a second hand one. If you cleaned your old one did you blow out the little gauze filter that supplies fuel to the high pressure pump. If it was mine I would hook up a pressure gauge on the rail, and I would want to see around 40psi.

[bassyac]

Just repowered with used 2005 df140s. Both engines idle fine but port motor loses rpm after a couple of minutes over 2000 rpm. If I leave the motor in gear, it will drop and go back up. Sometimes it will stay up for a little while and sometimes it will just drop back down. If it goes back up, it will go back down. Starboard works like a champ. I have changed low pressure filter, high pressure filter, changed the fuel vapor separator and low pressure pump. I have also switched to portable tanks just in case it is something to do with the gas tank. Also changed fuel lines. What else is can caused this problem?

My 2 cents
Do an ADVANCED SEARCH on this Forum ( Bourbon Macallan) Page 3. Went through an issue with my 2014 df300, a whole season of trying to get it right.
John

[lcraig]

I removed the check valve from the fuel tank on the boat years ago. I switched to portable fuel tanks to rule out the boat fuel tanks. I then switched the 2 portable tanks to make sure it was the tanks. I put a new used VST but still stalling. I haven't done anything on the fuel rail. This problem is not kicking out any error messages. I also replaced the fuel lines from the tank to the motor. I also had a friend manually pump the ball while running and it still stalled. Macallan's problem was close but he was able to stay above 3000rpm and run all day. I can get that high for a few minutes and then it stalls. If you drop the throttle a little without going all the way down to neutral, the engine will start getting enough fuel to increase the rpms back up but that doesn't last long before it goes back down. can this be caused by iac or fuel rail. I can switch those out between motors easily.

[Moonlighter]

Its a bit left-field, but have you checked for the well-known engine holder corrosion issue? Check the side of the engine just near the fresh water flushing port (look fir the plug that looks like a welsh plug there) for signs of corrosion and any resulting holes that might be letting exhaust gasses escape. If this is the case, the gases build up under the cowl and affect the engine running, especially at mid to higher speeds.

[lcraig]

no corrosion, I checked that prior to mounting the engines.