what is the best/cheapest/safe way to add 2 fuel tanks to one mpi motor? The motor is a merc 300 mag, 2005.
I know there needs to be a return line for each tank, just not sure how it should be valved.

Thanks,
Matt

What kind of boat do you have, and how big of a tank are you looking to add?

Rather than go to the trouble of trying to separately valve two sets of two fuel lines to and from the engine (and, I would assume 2 separate fill ports), would your installation allow you to just tie the two tanks together?

How do you "know" that there has to be a return line to either tank? Fuel injected boat engine from Mercruiser and Volvo Penta do not use return to fuel tank lines. They run the unused fuel in a loop on the engine, through a cooler and then back to the fuel rails. So that's one problem solved for you.
There is some particular Coast Guard or federal regulation about multiple tanks in a boat. Something to do with the type and placement of the valves. I can not remember what it is, but I read something about it on the iboat forums just a few months ago.

Where's Al with the CG regs?

Thanks!

Ok, this is what I would like to do. This is on a pontoon boat. It has one existing tank in the center pontoon, I have room to add another in a vented storage area. The problem is that the original tank is only 38 gallons, I'd like to add another 20 or so gallon tank. I need to be able to seperate the tanks. This is mainly for trips to powell. Each tank would then have it's own fill and vent.

I havent looked at it too much but I was under the impression that the return line needed to go all the way back to the tank. The only place that I have seen multiple fuel lines is at the fuel water seperator/filter housing. Coule it be that the return line ties in there?

Thanks for all the help.

Matt

One more thing.
I will not skimp on anything just to save a feew bucks. Everything will be marine and coast guard approved, fittings, tank, etc...

Lazy.....

Yup. But Al can quote the thing from rote.

Yes. That's it.