Knocking sound in port side

[AV8ORed]

Hi all.

I'm new to the carver boats. Just bought a 2000 carver 356 aft cabin. Has 7.4 mercruser' and a 7.3 kW genny. I bought this boat from FL. When I got it on the water for the first time in GA it ran good till we were halfway across the lake and the port side engine wouldn't hold RPM. It starts up every time and dose. OT run hot. Runs right on temp wise. I've been told the gas in the boat is probably old just want to run it by you guys before I call a mechanic to come look at it.

Please note that my Genny and the port engine run off same port side main tank. And I also have a problem with it revving RPM's and them backing down repeatedly for a few min then it shuts down. I can most of the time start it right back up only to have it do the same thing. I am attaching a video of the port engine running today. PLEASE HELP!!

Bryan
2000 carver 356 aft cabin twin 7.4 MPI

[AV8ORed]

Won't let me post the video I have

[waybomb]

Check/change fuel filters, clean out the or replace it anti-siphon valve, check the tank vent for bug nests. Those are the simple things to check first.

[AV8ORed]

Turns out I out that port side on the aux tank and after it ran for a few min it was WAY better. Now if I just had the same switch for the Genny.......

Guess I need a tank cleaned out or put additive's in it Along with some new gas?? It's at half a tank now. ???

[waybomb]

Did you check the antisiphon valve on the tank?
Clean the tank vent out?

[AV8ORed]

Don't know where those are located. Will have to really look around today.

Thanks for all your help and I'll let you know

[waybomb]

Anti siphon valve is at the fuel tank usually looks like just a hose barb but inside is a light sorting and check ball.

The vent should be adjacent or by the fuel tank. Usually a round chrome piece that had little screens around the bottom on the outside of the hull. Those get plugged up and then the fuel tank is under suction since no air can get in to replace the fuel drawn out.

[AV8ORed]

So the siphon one is the short little elbow with a cap on it?

[waybomb]

The hose leading to the selector valve is what it is connected to. Between the hose and the tank.

Since the hose travels lower than the fuel tank, they install a very lightly loaded check valve. If the hose springs a leak, without that check valve, you would empty the tank into the bilge and make a very Hollywood explosion.
The fuel pump should overcome the spring. But sometimes the check ball gets gummed up and sticks partially closed

[AV8ORed]

Turns out I think it's the auto choke on the genny not working..... So was like it wasn't getting fuel