Re: Merc 75 hp 1986 starving for gas at wot
Just a guess, but it might be the high speed windings on the stator starting to go.
If the spark were weak, choking it wouldn't help. Symptoms are about fuel delivery.
I've seen symptoms like this caused by a plastic bottle seal floating around in the fuel tank, occasionally plugging the pickup. Truth is, it could be anything from a plugged vent on the tank (bugs, usually) to a soft vacuum pulse to the fuel pump. When it balks, fuel level in the carbs is declining. Choking it pulls that out in a few seconds, and then it's too low for even that to fire.
The list:
Tank vent
Debris or sludge in tank
decomposing fuel lines
undersized fuel lines (usually on a v6)
fuel pump diaphragm or valves (discs)
fuel (bayonet) fittings
soft or plugged crankcase pulse to fuel pump delivery
dirt in carbs near jets
dirt in carbs behind needles.
Bear this in mind. When it's running lean it can do serious internal damage to the engine. You're not supposed to be able to inspect the wrist pins through the spark plug hole. Lean burn gets a lot of engines fer sure.
hope it helps
John
