[QUOTE=David M;1200760]Below the waterline?....absolutely not. Tell him to cough up the big money
for an adapter and do it correctly.
Don't Mickey Mouse around with below the waterline plumbing
that has the potential of sinking the boat
if it fails.
Chances are there is a NPT pipe thread (tapered thread) on the head that can be changed out from a 3/4 barb to a 1 inch barb. That would be the cleanest way of doing it. The less elegant way would be to find a 3/4 barb to 1 inch barb adapter.
Do not go down to Home Depot and buy brass...it will corrode away before you know it. You want silicon bronze, bronze oUr some sort of non-brittle plastic. Silicon bronze would be best if you can find it.
Use 3M 4200 and not Teflon tape to seal the thread
I am curious as to why you favor 4200 over teflon or regular pipe dope