Re: SHIFTING PROBLEMS
Sounds like your carbs go low at full throttle then refill at idle. Or, it could be something dumb like the fuel in the tank runs away from the pick-up in forward. (broken or misplaced fuel pick-up) This would only happen when the tank was low or partially filled. In reverse, the fuel sloshes toward the pick-up and the engine gets fuel and runs fine again for a while
First check the screen in the tank. Then check the screen on the fuel pump inlet. If either is gunked up, it may not be letting the pump work to full efficiency. Have you mixed gasoline containing ethanol with gasoline containing the other additive (I think it's called MBTA)? In the presence of moisture (boat tanks) this forms an insoluable floc which will clog filters and pumps. Either type alone is ok; it's the mixture that causes problems
Could be fuel pump starting to go bad and letting the carbs go low at full throttle. When you idle it fills them back up and off you go until the next time they go dry. Take the pump apart and check both the diaphragm and the check valves. The diaphragm should be quite flexible, not have any pinholes, and not be cracked. The check valves (3 of em) should be closed and open easily under either pressure or vacuum depending upon position in the pump. The plastic discs should have no cracks or cuts in them, and the valves should hold pressure or vacuum (again depending on position in pump)with very minor leakage acceptable. while you have the pump apart, replace the diaphragm and gasket anyway! It's a cheap preventive maintenance.
