Engine runs smooth for an hour then chokes

[bristolw66]

Hello friends,

I've learned allot over the summer and now it's almost over. Out of the 5 times I went out on the LI sound, I've had to limp or get towed back. This is my last attempt before packing it in....

Consistently, I would launch smoothly and run at around 10-15 knots for an hour. Then after the hour the engine would start to backfire, loose power, and even stall out (with a strong fuel smell). It definitely has a "flat spot" in the throttle that I have to play with to get/catch enough power to limp back to the dock. Then the next day.... it runs like there is no problem again.

So far I've:
Changed the Alternator
Added another Battery w/cut off
Re-terminated all ignition wires looking suspect
Found the coil not working when it refused to start at the mechanic
Changed the coil, cap, fuel filter, and plugs (but not the wires)... when the problem presented itself
Fixed the outdrive (I burned out ignoring the alarm... see previous post)

The mechanic I've been taking it to took it out (of course the ride was perfect) and he can't definitively find the problem (root cause).
However, he indicated finding a huge deposit of fuel when pulling the carburetor.

I've read all related posts to timing and the accelerator pump. My buddy recommended removing the carburetor and checking it again. I was wondering if the gas mixture is too rich and is there an adjustment that can be made.

I want to try one more time this last weekend of the summer.
Any thoughts?