Engine surging @WOT HELP!!!

[Bass Ackwards]

1999 Johnson 150 hp
My boat/motor has been sitting for 2 yrs. Emptied out all the old fuel, rebuilt carbs, changed fuel filter, added new in-line fuel filter in addition to one on motor, replaced spark plugs, checked for good spark, and performed compression check. All cyllinders were 105 psi or better (max of 115 psi).
Engine starts and runs fine, maybe a tad rough, idles at approx 1000 rpm, but when I go to WOT, when in the water, the motor died out repaetedly, but here in the driveway, the engine surges. Consistent power/loss/power/loss....driving me nuts. I've already replaced the squeeze bulb line from the fuel tank, nothing changed. Reset all the floats in the carbs to the same position when inverted, 12/16th" (book call for a range of 11/16"th to 1 1/8") still nothing is working. removed and cleaned what I believe are the low idle screws, and set them all to .590". Yet at full power, WOT, the motor still does the same thing surging from what sounds like full power, then dies off, over and over.
Any ideas?? If I can't figure this out soon, it's off to the shop for gos knows how long or how much!

 

[reeldutch]

Re: Engine surging @WOT HELP!!!

when you cleaned the carbs did you take of the port and stbrd trhottle bodys and clean them and replaced all new gaskets?.

reving the engine up in the driveway on a hose doesnt mean anything.
if 3 cylinders where missing you could still rev the engine up till it reaches the sky.
theres no load on it.

what happens if the engine surges and you hit the primer?
or bring a buddy and let him squirt some premix in the carbs while you run wide open so you can find out wich cylinders have a fuel problem.

could be a air leak in the fuel system.

be very care full running lean is a fatal 2 stroke disease.

good luck

 

[tashasdaddy]

Re: Engine surging @WOT HELP!!!

http://forums.iboats.com/showthread.php?t=244013

make sure you fuel tank vent is clear and open.

 

[Bass Ackwards]

Re: Engine surging @WOT HELP!!!

when you cleaned the carbs did you take of the port and stbrd trhottle bodys and clean them and replaced all new gaskets?.
yes

what happens if the engine surges and you hit the primer?
or bring a buddy and let him squirt some premix in the carbs while you run wide open so you can find out wich cylinders have a fuel problem. don't know, haven't tried that yet, but I will and I'll let you know.

be very care full running lean is a fatal 2 stroke disease.
how would I know if it's running too lean? If you are referring to the .590" dimension, that was measured from the throttle body to the top of the adj screw on thr body itself.

http://forums.iboats.com/showthread.php?t=244013

make sure you fuel tank vent is clear and open. checked the link, my carb looks nothing like that, I have nothing on the top center, but the high speed is in the float bowl, and thay are clean....tank vent appears clear/open and free of obstructions.

Thanks!

 

[Mas]

Re: Engine surging @WOT HELP!!!

Squeeze the fuel line bulb when it surges...if rpms improve, you may have a fuel pump issue.

MAS