J140TLCDC When warmed up engine dies as you accelerate.

I feel I am having a run of poor luck this whether, one issue just leads to another. New issues today, once the engine was fully warmed up, I had been cruising at between 3000 and 4000rpm for about 80 minutes, I slowed and went to neutral for about 5minutes. The boat was idling at 800rpm, sounding very health. I then advance the throttle to take off and as soon as I reached about 2000rpm the engine would die back. I throttled back quickly and the engine although in gear recovered at about 1000rpm, Pushed the throttle forward again and the same thing. On the third occasion as I pushed the throttle forward I pushed the key in very quickly and not an issues the boat was straight on the plane and running smoothly at 3500rpm. I ran the boat for another hour at 3500rpm and drew along side a pontoon. Was tied up and in neutral for about 3mins, pulled away from the pontoon and pushed the throttle lever forward, again at 2000rpm engine died back to 1000rpm. Again I throttled up but pushed the key in quickly to give a quick shot of gas from the solenoid, no issues, boat picked up properly. Any ideas? Additional information: Engine runs great and pulls all the way to 6100rpm, I opened it to full throttle so see if the fuel pump was not delivering, but not an issue, was at 6100rpm for about 2mins. Plugs are tan, no timing issues. I think it must be fuel, but I have just rebuilt the carbs and it has run for 10hours since carb build without issue except for the occasions today.

sounds like fuel delivery to me also..you could have a siphon problem where the gas is going back to the tank when you reduce suction on it...or a air leak...the first thing i would do is replace the bulb and check the oring in the connector that attaches to the motor...then the next thing i would do if it still fails is to pump the bulb before you accelerate after an idle or stop and see if it still fails...did you change anything in the routing of the fuel hose?any loops curled up in bottom of boat?any dips in the line...you probably have an additional anti siphon on the fuel pickup at the tank...

Papyson, thank you for the reply. I changed the fuel line and bulb at the start of this season, so it has only been on the boat for 4 months, it does pump rock hard and will stay hard so I do not think it is siphoning back. I also replaced the fuel pump at the same time. I will check the O-ring in the connector that attaches to the motor. I did not change the routing of the line and it is strange that it does not happen when it is cold, the little bandit (not to use bad language) only starts to play up once warm. It did it again today and we were skiing so not ideal. I will try pumping the bulb and see what happens. Pushing the key in quickly prior to accelerating is what we did today to get around the issue. One last point, if it was the anti siphon in the fuel tank or the bulb would I not have idling issues? It will sit in natural and purr away, put it in gear and the engine will pickup but at about 2000rpm dies back.

Sounds like its lean in the intermediate stage, this can be caused by air leaks on mounting o-rings,loose carbs or loose/leaking throttle plate bodys or side cover gaskets on carbs. Also wear on the motor and improper cooling can cause this as small bores are picky about this. Also if air box is not complete(baffle removed) this will cause a lean issue, a quick test is to run engine till problem arises and remove air box cover, insert tooth oick in intermediate jets and trey to pplane ,if it jump up on plane its lean so check listed and no problem/s found rejet.

faztbullet thank you. I did rebuild the carbs about 6weeks ago and used a torque wrench. The cooling was an issue and I replaced the thermostats and diaphragms 2 weeks ago. I did find when testing post thermostat replacement the Port head heated higher than the starboard, I found a blockage in the very thin pipe at the Tee connector (the Y connector before the pee stream) not allowing the air to escape from the port head hence stopping proper water circulation. I replace the connector and both heads at idle were at 143 degrees F. I have not look at the throttle body plates, so will do that and I did not replace the jets when i did the car rebuild, I did check they were clear, so I can replace the jets. I will check the airbox to see if the baffle is there as I have only owned the engine for three years. One last think, I note if I tilt the engine up fully and it is turned hard to starboard athen leave the engine overnight the next morning there is a small pool of two stroke oil, in the corner where the accelerator cable enters the lower cover. I am sure there is petrol there too but it has evaporated leaving the oil as evidence. This has only happened since the car rebuild. Thanks you for the pointers I will check them out in the next few days.