Engine misfiring - got any suggestions?

[footloose42]

Hey guys, new to the forum but not new to skiing. My university's ski club has a 2005 Moomba Outback which has recently started having some problems. Everything is fine until 3500 RPM, at which point the boat starts jerking. It basically feels like someone's constantly punching the throttle and pulling back, punching the throttle and pulling back, etc.

We think it's the engine misfiring at the second stage due to the consistency in the RPMs where it occurs. We first tried replacing the fuel filter, but that did not fix the problem. Does anyone have any suggestions on where we should go next?

[kaneboats]

Inconsistent fuel supply could be the problem. It's possible the fuel pump is going out. It could also be an ignition problem but the fact it will run up over 3000 rpm without incident makes me think fuel, not ignition.

[ga-lsv05]

A misfire and a rpm surge would feel like 2 completely different situations. Need a better description or a video to help more. Also is it carb or efi?

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[footloose42]

I wont be able to get a video for a little while, but maybe this will do for a description:

Have you ever accidentally red-lined in your car and hit the rev limiter? that's pretty much what it feels like.

I want to say it's efi but I'm not certain.

[KSmith]

I'm going to go with fuel pump. sounds like it may be fuel starvation

[ga-lsv05]

I would also lean towards a fuel issue

2005 mobius lsv 2900lbs ballast

[footloose42]

sounds like we'll look into replacing the fuel pump then!

[ga-lsv05]

Determine if its carb or efi as well because if its carbd this could easily be a carb issue like a dripping or clogged venturi or a primary jet problem

2005 mobius lsv 2900lbs ballast