Maybe you need to go back to basic testing like compression test. Post your readings as soon as you get it done.
Compression tested. All cylinders within 2PSI of each other, roughly 140PSI. (Old dial gauge isn't that reliable. Took reading 4 times per cylinder and got ~140)
Does it spit back out of the carb? no? then the reeds are probably good.
The valves in the pump test them and see if they are sealing right?
Clean the carbs again.
Making sure the main jet's not clogged.
Was working on a motor it had the same problem.
I cleaned the carb 3 times and finally #3 did the trick???
I never did see anything in there it just started running better.
Install a filter between the carb and the pump.
Replace all the hoses and inline connectors.
The squeezie too.
The squeezie can be bad right out of the box.
Check all the trigger connections.
Sometimes when advancing the throttle the wires move and loose contact???
Excessive fuel use? Did it ever run right?
You change the prop lately?
It doesn't spit fuel out the carburetors as far as I can tell.
The "valves"? Are you saying there's more to the fuel pump than the diaphragm? Are there check balls or something in it that may have somehow failed?
I will clean the carburetors again today (if I have any more carb cleaner..) but probably won't get a chance to try it out today.
There is a filter there already. It was there when we bought the boat.
Replace all the hoses seems unnecessary.. unless there's a blockage. If there was a blockage, it wouldn't use so much fuel I'd think, but I will replace them anyway.
The squeezie (primer bulb?) was just replaced with a brand new one as the old had dry rotted. They can be bad out of the box? They consist of two one way valves and a bulb, right?
The trigger wires were tight last I checked, but again, I will check them. That sounds like a very plausible cause right there.
It never ran right since we bought it.
We have never replaced the prop. It's in good condition, though.
If that fuel pump is using the crankcase vacuum/pressure pulses and is ruptured, then it can suck fuel straight into the engine bypassing the carb(s) and that could also be a cause for the situation. But you stated you already checked the fuel pump. So I would recheck the fuel pump, the carb(s) and even the reeds IF the compression checks out okay. JMHO!
I'll probably just replace the fuel pump diaphragm as the gasket behind it is hard and seems brittle.. probably means it's old and needs replacing. I'll recheck the fuel pump, reclean the carbs, and pull the intake apart and check the reeds.
Thank you all for your help so far.