Can`t get above 2000 RPM, Engines back Firing

[marklo154]

Was out today, putts around for about 45 minutes, everything seemed to be running ok then I lost the one engine. No big deal it fired right back up but then both motors started running a bit rough. After a few minutes of this things seemed to get better, went to speed up made it to 2000 rpm and she wouldn`t go any farther both engines started back firing, I crawled back into the dock, with both engines and docked. Seems strange that it is both engines. At the dock while in neutral both engines would run at 3000 -4000 rpm not back firing no problems.

Anyone have any thoughts. My first thoughts was fuel but I have run the boat twice since any fuel was added tanks are 1/2 full.

[ready123]

Partially blocked anti-siphon valves at top of the tanks..... which do not allow high fuel flow which you do not hit on no load running at the slip. What happens in gear at the slip when you try to up to 3000? Tighten lines first

[RWS]

Partially blocked anti-siphon valves at top of the tanks..... which do not allow high fuel flow which you do not hit on no load running at the slip. What happens in gear at the slip when you try to up to 3000? Tighten lines first

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Good call, Mike !

RWS

[marklo154]

I will check that out, I find it strange that it is both engines thou. The tanks are not bridged .

[dagen]

Can you explain how to check for blocked valves, and if they are blocked how to fix the problem?

[P-Dogg]

how to check for blocked valves

They are located at the tank outlet. Remove them and inspect the incoming side. They are usually blocked by something obvious, such as a debris that is easily visible to the naked eye. Google "blocked boat anti siphon valve" and you'll get 64,700 results if you want to read up on it. You should be able to force compressed air through them in the forward direction, but not in reverse. Their purpose is to create a blockage that the fuel pump can easily overpower, but that the suction of a leaking fuel line can't. Keeps all of your fuel from draining out should a line that goes below the fuel level develop a leak.

And welcome to the forum!