2002 - F50 hesitation on take off

[railroad3380]

I have a 2002 F50. When you give the motor enough gas to get the nose out of the water (maybe 5-8mph) you can feel a lot of hesitation in the motor. But if you are in idle or on plain there is no hesitation. Spark Plugs are good, cleaned carbs with carb cleaner, and added startron to the gas. 100% fuel is the only fuel that has ever been run in the motor. When I looked in the small filter on the side of the motor there was some black specs in it. My guess is there is water in the gas or my fuel line is breaking down. Or both.

[railroad3380]

I replaced the spark plugs and fuel line today and ran the boat. Still doing the same hesitation at low speed. I also pumped out about 1 liter of fuel into a clear container and let it settle for one hour. I did not see any signs of water in the fuel. I did notice when I run the motor with the "rabit ears" and put it in gear there as a very noticable vibration in the foot. The motor has never done that before. I read on previous post that some vibration is expected when cranked out of the water.But previously cranked out of water and in gear it was really smooth. Would a problem in the foot cause my hesitation at the slow speed.

[boscoe99]

Were the carburetors completely disassembled and cleaned in a heated ultrasonic cleaner? There is no other way to ensure that they are thoroughly cleaned. There are some incredibly small passageways within the carburetor and it is difficult to get any debris out that gets in the carburetor.

Particularly troublesome is the accelerator pump circuit. The nozzle has an opening about the size of a nanoparticle. If you have the air box removed, and if the throttle is advanced quickly, do you see fuel being sprayed into the throat of the carburetor?

The condition you describe sounds to me like the accelerator circuit, which I believe your carburetors have. These things run on the edge of leanness to the point of almost being extreme. Whenever the throttle is opened air goes in easily. Fuel, not so much. If the amount of fuel does not keep up with the amount of air the motor will hesitate and stumble. Sometimes it may die.

Are you running ethanol in your fuel supply? This causes the fuel/air mix to be leaner than it is on straight gasoline. It can make the problem worse. Some folks find they have to go to larger size idle mixture jets to help with the situation.

I don't see any connection between the lower unit and a stumble upon acceleration.

[railroad3380]

100% gas is all that has ever been used. I took the tank out and cleaned it today. There was a good bit of fine black pieces of trash in the fuel. The carbs were disassembled and sprayed with carb cleaner. No ultrasonic cleaning. The marine shop where I purchased the sparks plugs said the carbs could be out of sync.

[boscoe99]

Yes, if the carburetors were not synchronized when put back together they won't run as efficiently as they might otherwise do.

[railroad3380]

Would the vst filter cause this hesitation that I am describing?

[rodbolt17]

the 2002 F50 is carbureted, does not have a vapor separator (VST).
the accelerator pump does NOT throw fuel on that model.
it simply adds a small amount of air pressure to the float bowl chamber and only works when the engine is running.
when cleaning you must drill and remove the idle A/F mixture fuel plugs.
when reassembled you MUST use a 4 channel manometer to correctly sync the throttles.

[TownsendsFJR1300]

If your finding black spec's in the filter your probably right, the fuel line is breaking down. If any of those spec's got past the filter and into the carbs, it could get pulled up into the small orifcies (jets) mentioned above.

I would think the carbs have a drain screw in each of them. With a small catch can (I use a tuna fsh can) under the float bowls, remove the drain screws and catch what comes out (looking specifically for the black, possibly rubber stuff). Squeezing the primer bulb will help flush any crap out of the bowls.

As noted above, you really have to manually remove the jets to clean them. Besides running something theu them, hold them up to the light and VISABLY LOOK THRU THEM.

The covers RB spoke of, covers air screws for the idle mixture. Besides cleaning those out, generally opening them (should be counterclockwise) richens up the low speed mixture and will clear up that hesitation if the carbs are Visably (the jets) clean.

And find what hose is breaking down and immediatly get rid of it, you'll be chasing your tail around...

Good luck..