Twin Merc 3.0s stalling during throttle up

Twin Merc 3.0's (1999) stalling during throttle up. Both crank and idle fine, and I am able to get boat on plane but then both engines will stall out after about 10 seconds. Then they are tough to crank but will after some coaxing. They'll idle fine, but stall again once I throttle up.

Any ideas where to begin to look?
Thanks

Re: Twin Merc 3.0s stalling during throttle up

When you start them, do you give them some throttle (1000 to 1200 rpm) while the warm up and the choke opens. Carbed engines are like that when cold.

Re: Twin Merc 3.0s stalling during throttle up

Yep,,, both engines are warm. I assume both chokes are opening but havent taken breathers off to check. I will go down and have a look.

Thanks

Re: Twin Merc 3.0s stalling during throttle up

Howdy,

It seems unlikely that both engines would have exactly the same problem. They ARE however, fed fuel from the same source?

If so, you may have a partially plugged fuel vent or pickup screen.

Re: Twin Merc 3.0s stalling during throttle up

Correct HG32...the fuel for both motors are coming from same tank and share the same pickup tube. I have a T valve that splits the line into two after it leaves pickup. From there, the separate lines go to their own fuel filter/water seperator, then on to engine.

Tried bypassing fuel filters and pickup tube by running the lines directly into tank through an access hole. Also left the fill cap open to rule out clogged air vent. Also checked both chokes to make sure they are opening.

Both engines still did same stall as before...They crank and idle fine, but upon throttling up, they will run for a few seconds, then start losing power and die out.

Seems odd that both engines are doing same thing at same time and the issue not be fuel or fuel line related. Scratching my head.

Re: Twin Merc 3.0s stalling during throttle up

Try running 1 engine on a remote tank.

Re: Twin Merc 3.0s stalling during throttle up

did you check the water separators?? pour the contents into a glass jar and inspect

what are you running for fuel?? fresh/old, ethanol, non-oxy??

just because you bypassed the filters dosen't rule out the fuel itself being suspect