Hesitation on acceleration under load

1980 Ski Nautique with 351, when pulling out of the whole with gradual acceleration I can feel the engine pull and hesitate and pull again, it feels like the engine miss fires, this happens until you get to a certain speed but when accelerating fast it's fine.

What could be the problem.

It doesn't happen all the time on mine either, I have the distributor and I already checked the cup, roter and plugs all look fine. It does it after about half hour being on the water and only when under load. I will try to take off the fuel filter to see if its restricting the gas flow too much.

Thanks

If I read your post correctly:

Slow acceleration hesitates.

Hard accelaration or WOT is good.

Doesn't sound like a fuel "restriction" or the condition would be worse at WOT. Sounds like the Primaries in the Carb.

Check the Choke operation.

Your carb has an Accelerator Pump and Power Valve (Holley) that smoothes the transition from idle to WOT. Sounds like they're working fine. During slow acceleration, your fuel is mainly from the Idle mixture and Primary circuits.

To make sure the Accelerator Pump is working, look into the carb and pump the gas and make sure she "squirts". Easy part is over...

Then I'd suggest you check the setting of the idle mixtures first...typically 1 1/2 to 2 turns out and then fine tune for max engine vacuum or RPM. If you can, reset the Idle to 800 RPM and then check your engine timing. At this point, you know the Idle Mixture is correct, Timing OK and Power Valve and Accelerator pump working.

After that, a slow acceleration depends on the primary jet size or debris in same.

Lot of guy's here run Holleys...if you do dig into the thing, post your jet sizes and power valve spec's and you'll get some great input. Hopefully, this post will stir up some of the Carb Guru's...I think that's your problem.