Outboard motor Techs: Motor pulls back when accelerating

2 stroke?

High speed jet in carb is clogged.

I know that this sounds crazy. I still not sure I believe it but a friend had a similar issue on a Yamaha. Shop did lots of fuel work. Eventually wanted to change what I believe was 2 fuel pumps. Turned out a loose connection on the battery corrected it. How? I have not given it much thought and I am not close enough to his boat to see it but worth sharing none the less

If something electric runs the timing then it needs the right voltage to work. Over or under voltage and it can throw it off. Buddy of mine’s fourwheeler wouldn’t run worth a shite unless he turned the lights on. He put a cheap Chinese voltage regulator on it that was supplying too high to the CDI, when he flipped the lights on the draw would drop the voltage back to where it liked.

Fuel filter

Water in fuel would jack it up in idle worse than high rpm, so probably not moisture issue in fuel.

Replace fuel/water separator and filter under cowling. If problem persists, get carbs looked at. Remember, the oil that lubricates your engine travels with the fuel. If you have blockages, you’re not only starving the engine for fuel (which raises combustion temps by itself and could burn a piston), you’re also starving it for oil. Don’t fool around with this for too long. Get it fixed.

Check your fuel pick-up tube. It is where your fuel line connects to your fuel tank. The tube is a hard PVC type tube that goes into your gas tank and at the top is a metal 90* fitting where your fuel line clamps to. In that 90* is a check valve. With your motor being a 2004, its very possible that the check valve in that tube is sticking. It can allow for a motor to idle but will restrict flow and starve the motor when you accelerate. The piece costs less than $25 and is an easy job to replace if your fuel tank is easily accessible. I've had this same problem you described. Hopefully it is the same fix.

I would start with the fuel lines. Easy fix if that is the problem. The inner liner can separate from the outer line, causing it to collapse when accelerating and blocking the flow. When it goes back to idle the line is able to keep enough fuel moving to keep it running. This creates the problem that you describe.
The outside line will look normal so sometimes people think that the fuel line isn't the problem. I would start there.

New fuel lines are cheap. If yours has a hole or leak where air can get sucked in, you can have issues similar to what you describe.