Engine is "missing" when going in/out of neutral...
 

I have a 98 Moomba Mobius and the engine sounds like it's missing at one particular speed. It's happening when I shift from neutral to the slowest speed in both forward and reverse. If I give it enough throttle to go faster it sounds fine, but that's really hard to do when I have a rider in the water and trying to tighten the rope.

The problem is the same in both forward and reverse. If I don't give it enough throttle the engine knocks a little and sounds like its going to stall. If I go back into neutral its fine. I recently had the carb rebuilt and don't think that has anything to do with it. Any ideas??

I did also notice that the rpm's seem to be too low at these speeds, close to 500...

Is it a Holley carb?

Have you checked your plugs/wires? When you shift, the engine rpm's will drop lower than idle because it's now under load. May want to check your fuel filter as well. Maybe also add some fuel treatment to the gas. I had a similar problem and come to find out it was the ethanol in the fuel. I now treat every tank with Marine Formula STA-BIL. Good luck.

Does that Marina formula STA-BIL help a lot, is it a pretty noticeable difference?

Aaron - It is a Holley carb, what makes you ask?

Chris - Plugs were next on my list to change. What wires are you talking about?

After rebuilding a Holley. I have seen people that forget to make sure the accelerator pump on the front bowl is adjusted correctly. What can happen is there may be play in between the pump and spring loaded nut and bolt. When you put it in gear the throttle starts to open the butterflies/blades. when that happens it should get a small squirt of fuel. when not adjusted correctly it will get the air in but no fuel. This will cause a slight hesitation or bog. When given enough throttle though it's fine because it gets the squirt of gas it needs. Did this start after rebuilding the carb?

When you replace the plugs check out the terminal connector inside the spark plug wires. Also check the connectors on the distributor side of the cable. While you’re there also check the contacts inside the distributor.

As for the STA-BIL, it cleared up my issue with rough cranking. With all the posts on ethanol issues and it destroying marine fuel systems I decided to start treating the gas. I live in NC and some stations have less ethanol than others. I try to find stations with a lower amount but they all have it :(

Interesting, my issue started week #1 after the Holley carb rebuild...thanks for the heads up on that.

I'm in Virginia and are stations all the same too. Have you ever been out on lake Gaston? I'm picking up a bottle of STABIL this weekend and giving it a shot. Couple be the cheapest fix of all.