Gas Tank check valve
 

Currently converting over to Holley MPFI and curious if my best bet regarding the gas tank check valve, (original circa 1993) would be to replace with an external one way check valve, or replace with tank mounted style? I Will be using Holley EFI fuel pump. Thx

I know you are supposed to use them, but they are so restrictive I remove them...

So the issue with that is obviously you run the risk of fuel siphoning into your bilge, should you have a leak? I agree that they are restrictive. I know someone will bring up the insurance company denying your claim should the boat ever catch fire, however that's unlikely. I am more concerned with my wife and child's safety regarding anything I do to this boat. If it seems relatively safe to delete it, I just might. We will see. Thanks for responding. Must be a beat to death topic here....

We remove them all because of their restrictiveness. Actually, very few new boats (especially custom boats) have them that I have seen.
Eddie

Thanks for the responses! Eddie, you do make a great point, and after posting this I was discussing my fuel system with Alex Haxby(bought Holley HP MPFI from him) and he gave very similar advice to yours. Plan to drain the fuel tank, remove the pickup and see what ID the tube is. If it's too small, I will need to remove the tank and address that. Either way I will definitely ditch the check valve.

If it has a removable pickup tube and it isn't large enough, let me know if you need one made. I have made quite a few that are 1/2" id with a #10 male fitting on top. They are all SS and will supply just about any hp engine you can put in.
Eddie

No, that's the direction the check should flow anyway.

on most performance boats the tank is lower than the engine/pump so siphoning should not be a issue anyway...

From reading up on it, seems its a safety feature that pretty much all builders used back in the day. I'm just going to delete it and use a larger pickup as mind is too small to support my planned 625hp engine. Thanks guys!

coast guard reg's said that there had to be a way to prevent fuel from siphoning into the bilge if a hose fails (or at least used to, not sure if that has changed). they allow this in a couple of ways. one is the anti-siphon valve (what you have now) that requires a small amount of vacuum from the pump to pull fuel through it, it then closes when the pump is off and a leak in the hose is not enough to open it so it stops the fuel flow. the second is a ball valve at the tank that can be closed by hand. if you use the valve is has to be accessible with out opening the engine hatch (under the seat or floor thru a cover). this is what most builders do now to make the insurance companies happy as the anti-siphon valve only flows enough for about 400 horses and only if the pumps are strong. lots of boats suffer from a lean condition because the pumps get a little old and do not pull as well as a new one and they started out on the edge of overcoming the valve when new.

Marine gensets normally have an electric valve that opens when voltage is applied .Gensets have such small pumps they have trouble or can't pull through a check valve .Curious why main engines don't use this ,or do some? On regular old stock stuff I always leave anti syphon valve in just to cma. Big power ,big pickups ,big lines and no check valve. I've always wondered what would happen IF the unthinkable happened and the insurance company was looking to pass the blame. As compedgemarine stated "used to be required" to meet uscg spec. I assume they are still supposed to be there ?

I said 'used to be required' simply because I have not read the CG manual in at least 6 years so I dont know if it has changed. on anything with any kind of power I install a ball valve as they do not change the flow and you can just pop the cover off under the rear seat and shut them if there is a problem. all the CG cares is that if the engine or belt failed and the fuel line is cut, fuel can be shut off without opening the hatch. the 46 Cougar I did a few years ago does not have any valves on it as there is no way to get to them without opening the hatch as it has side tanks in the engine compartment next to the front engine (triple) and has 1050 mercs. on that boat you just have to hope there is not a problem but what else can you do?