Chrysler 440 fuel pump Marine vs Auto?

Have been running a 28ft Cary with the twin 440's. When I purchased it, I went through all the hoses, etc.. I also replaced the fuel pumps and purchased them from NAPA locally(part#M6767). They were pumps for auto application for the chrysler 440. They looked identical to the ones I replaced, including the diaphragm vent tube that connects to the carburetor, except the originals were stamped CARTER. Have been running them for 2-3years without problems. Am getting ready to go through hoses belts, etc again but have wondered about these pumps since I did this. Anyone know if there is a performance difference between the pumps? If so, please explain and I will go ahead and replace them this season.
Thanks

 

This is the part you should have which replaces Chrysler 3745415 and is a Carter M6767. I'm fairly sure this is now a Mallory part (MAL9-35401), but you're fine, it's the right part. They are prone to rust, particularly in a salt water environment, so consider some form of protection.

 

If it has a vent tube, it must be a marine version.

 

Thank you

Thank you PAR and GONZO. The pump has the vent tube.

 

Remember to connect a hose from the vent to the carburator for it to work

 

Can somebody explain to me why the marine pump needs a vent and the automotive one doesn't?

 

The marine version has a double diafragm. If the one that pumps fuel breaks, the fuel stays between the cavity and gets sucked into the intake. This prevents the fuel from filling the crankcase or the bilge. Automotive pumps vent into the road.