Boat sputtering at full throttle

[RinkerCap]

2001 Rinker 212 with 5.0L mercury. We have had a lot of rain here in the past month and I have not had the boat out in that time. It was sitting at less than a qtr of a tank yesterday before we went out. I took the gas cap off to add fuel treatment before I filled up. When I loosened the gas cap, a lot of air was released. I didn't think anything of it until today. We went out on the river and it ran fine for about 2 miles. After that, it started to sputter when I was above half throttle. Loaded it up and came home. I'm hoping its tank vent, mainly because of all of the air that was released before filling up, but not sure. I don't see the vent that runs to the outside of my boat like most. Any idea where the vent might be located if not external?

 

[Bondo]

Ayuh,..... Welcome Aboard,..... While the vent sounds like it's plugged, the entire fuel system is suspect,.....

Check the fuel filter for water in it, 'n Replace it,....

 

[Fun Times]

Sometimes the vent is at the fuel neck filler. If so, usually you'll see a smaller secondary hole when you remove the cap. Or look at the backside of the filler neck for a smaller hose running up to it along with the thicker hose that fills the tank.

If not, try looking at the tank and follow the smaller vent hose the best you can.

For a test while on the water during the bad running event, open the fuel filler cap and see if it runs better.

Good luck.

 

[superbenk]

Also check that your anti-siphon valve isn't getting stuck. Anti-siphon valve is on the tank where the fuel line attaches to the pickup usually at a 90 deg fitting.

You can also try bringing a portable gas tank (5 gallon tank or outboard motor tank) and plumbing it directly to your fuel pump to see if that runs better which, again, would point to problems in your fuel line or pickup or bad gas.