won't run under load

Out a few weeks ago, ran great for several runs. Then would not accelerate. Started fine, idled fine, accelerated fine in neutral. In gear would not accelerate. If I eased it up it would die. If I pushed it hard, it would sputter backfire and die. Finally nursed it home. Seemed like a transition circuit problem in carb. Took carb off, disassembled, cleaned, ran good for two outings. Failed me again last night. All exact same symptoms, only this time I could not nurse it home. If its crudding up, maybe I need fuel filter, but based on last time and the fix, that's all I can think of. It's an Edlebrock, so not your typical Holley problems of adjustmenjts or power valves. Any thoughts? (And don't bother telling me its because its an Edelbrock, seven years of pretty trouble free use, so that is not it.)

Thanks.

Funny you should ask that. Last time it happened a few weeks ago, one of the acc. pump jets was plugged and I was getting nothing out of one side. My clean out took care of that. I didnt have a chance last night to check that out. If that's it again, I would say I have a cruddy gas problem (new batch of gas, but maybe crud in the tank.) Also, maybe the aforementioned filter problem. That's a pretty cheap fix (along with another clean out)

Probably a good thing we didnt go out last week Brian. We might have ended up stranded. on a strange lake...fortunately last night I was near a friend's dock that I could limp into.

I went back with my tool box to rescue my boat last night. Of course it started right up and ran like a top. That kind of makes me think it wasn't a gummed up carb, but rather one of those pesky, impossible to diagnose, time/temperature related ignition problems. I ran it a while to get it hot to see if it would recur, and of course it didn't. I know the ususal suspect is a heating up coil. I had this similar problem a few years ago. Wasn't coil. Auto mechanic friend said my cap was shot and with heat and expansion, contacts went bad. Cap is only a few years old and I don't consider caps maintenance items, but maybe I will start with cap and rotor and wait it out. Any other thoughts?