Stalling at headway

[Sea Guardian]

Another question; 4.3L MERCRUSER alpha thunderbolt V. When under head way speed, idle but in gear, boat stalls out. Runs fine on the dock, will idel for a long time no issues. Took it out a little ways at idle speed ran fine. Got up onto plane, back off plane back on plane ran fine. Idle on the way back to the dock stalls out repeatedly. Start right back up no issues.

 

[tank1949]

Another question; 4.3L MERCRUSER alpha thunderbolt V. When under head way speed, idle but in gear, boat stalls out. Runs fine on the dock, will idel for a long time no issues. Took it out a little ways at idle speed ran fine. Got up onto plane, back off plane back on plane ran fine. Idle on the way back to the dock stalls out repeatedly. Start right back up no issues.

sounds like starving for fuel on high demand. check for blockage in fuel pick up tube and mud-dobber nest in fuel vent. Been there!

 

[itsathepete]

Another question; 4.3L MERCRUSER alpha thunderbolt V. When under head way speed, idle but in gear, boat stalls out. Runs fine on the dock, will idel for a long time no issues. Took it out a little ways at idle speed ran fine. Got up onto plane, back off plane back on plane ran fine. Idle on the way back to the dock stalls out repeatedly. Start right back up no issues.

Carb or tbi or mpi?

 

[Sea Guardian]

Carb or tbi or mpi?

Carb.

 

[itsathepete]

More info, please. Engine serial # if possible. 2 or 4 barrel? What year? What maintenance has been done.

 

[Sea Guardian]

More info, please. Engine serial # if possible. 2 or 4 barrel? What year? What maintenance has been done.

New plugs, New wires, New coil, New ignition pick up, cleaned carb, New fuel filter/water separator, New carb filter, New fuel lines, fuel pump psi @ 8. '06 ish, 2 barrel mercarb. Timing was done at beginning of season.
she purrs nicely at the dock, go out at headway speed fine go up on plane a couple of times and then on the way back at headway stalls out. Engine is @ temp, starts right back up after stall.

 

[itsathepete]

Engine should idle at 550-650 in gear. Sometimes tachs are not accurate so a digital tach or strobe can be used to verify actual rpms. I have successfully used a strobe tach app on my phone to verify idle rpm. You can also adjust idle mixture screws and see if it helps.

 

[Sea Guardian]

Engine should idle at 550-650 in gear. Sometimes tachs are not accurate so a digital tach or strobe can be used to verify actual rpms. I have successfully used a strobe tach app on my phone to verify idle rpm. You can also adjust idle mixture screws and see if it helps.

I tweeked the idle mixture a little this morning, we are going to go out today so we will see what happens. Maybe while I am at idle I will pop back there and make a small adjustment. I set the carb back to default idle mixture I figure I will start there. I don't have access to a digital tach so I think it will have to be by trial and error.

 

[Sea Guardian]

Engine should idle at 550-650 in gear. Sometimes tachs are not accurate so a digital tach or strobe can be used to verify actual rpms. I have successfully used a strobe tach app on my phone to verify idle rpm. You can also adjust idle mixture screws and see if it helps.

It does not sputter when she stalls just stops. You think it might be too lean or rich? Lean i think is out on the screw and rich is in on the screw.

 

[nola mike]

It does not sputter when she stalls just stops. You think it might be too lean or rich? Lean i think is out on the screw and rich is in on the screw.

8 psi is a bit high, check down your carb throat and make sure you're not dripping fuel at idle

 

[Sea Guardian]

8 psi is a bit high, check down your carb throat and make sure you're not dripping fuel at idle

It does not seem to be. I will pull the arrester off and look while under way. More to follow. If it gets worse, I have a tow contract.

 

[itsathepete]

It does not sputter when she stalls just stops. You think it might be too lean or rich? Lean i think is out on the screw and rich is in on the screw.

They should be fuel screws so in is lean and out is rich. I like to adjust while running and listen for rpm change. I go til fastest idle then 1/8 to 1/4 turn richer