Yamaha F150 & T9.9: Check ball valves in the gas lines?

[Moose-Hunter]

Curious...

I was examining the fuel delivery system(s) on my new boat and found something that baffles me. One engine's gas line has a check valve at the "T", the other does not.

It's a screw on, male barbed fitting in a brass "T". It accepts gas from the filter/water separator, splits, one goes to the main engine (F150) the other goes to the kicker (T9.9)

With the way it's been plumbed, I can't tell which engine has the check valve. It reads "30" on it...

Question... Which engine would get this check valve and why.

Thanks...

[Surface Tension]

Even though there is a check valve in the primer bulb of the kicker you don't want any chance of the F150 pulling fuel and eventually air from that line. So you want the check valve on the kicker line. Of coarse you can only run one engine at the same like this.

Give that a try, if you have any fuel starvation to the kicker on account of the check valve go with a 3 way switch instead.

I say that because the pickup tube in your gas tank has a check valve on it also. Adding another to the mix might cause issues for the kicker.

[Moose-Hunter]

Thanks Frank!

I tried it out last night in the configuration you described. With the check valve on the kicker side. (Was THAT ever a job!) No issues with starvation to either engine.

This gas system is full of check valves! One at each primer bulb, one at the "T", and one at the pick-up? This seems excessive. Are all of these really necessary?

[Surface Tension]

Yes there are.

You need the primer bulb to get the fuel to the carb to start the engine. Without the primer bulb you'd have a lot of excessive cranking. The check valve in the tank prevents gas in the fuel lines from running back into the tank when the engine is off plus if you should happen to have a fuel line disconnect the check valve in the tank will stop the fuel from running into the bottom of the boat.

The check valve in the T is to make sure your primary outboard can't suck air from the kicker in case the primer bulb on the kicker failed.