I have a 2" though hull for my main engine raw water intake and was told I can T off of this after the strainer to get water for my March pump. I am told there is plenty of water in that line which wont effect the cooling of the engine and its one less through hull I have to worry about. Any thoughts on this?
Well, it's pretty easy to figure: If the March pump takes a 1" diameter hose, and the engine takes the same, 2" intake with a T is probably fine. Just remember that the March pump line may want a siphon break at some point, but the MMA folks can tell you about that. Also be aware that the amount of condensation from the chilly side of the unit is going to be phenomenal: you are definitely a candidate for that pricey Venturi unit that sucks it up and shoots it over the side. Below my 12,000 BTU unit is one of the few rusty spots on my steel boat, and I am thinking it's perhaps something I should consider.
I have a four-inch standpipe with four ball-valved Ts: one for the engine, one for the Lavac head, one for the March pump and a spare, which I'll probably use for a salt-water tap in the galley.