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Hi Guys...Replacing all the thru hulls in my 1980 FBC....Can I get by with 1 1/2 inch Full Flow Intakes for either a 250 or 270 Cummins repower?? Also, What size thru hull for a future Generator application?? Thanks, John

I think you'll need to go to 2" full flow. Keep one of your old 1.5" valves for your generator. You can use a reducer to get the valve to accept the 1" hose that the gen-set will most likely want.

My 504's had 1 1/4 inch valves which are shot...So 1 inch for the gen set is pretty much universal for up to 5-6 KW??

Well.... obviously you should use whatever the manufacturer recommends. I have 2" full flow valves for my 230 Yanmars and a 1" full flow for my 3.5kw gen-set. The tip (I should think) is the size of the inlet fitting on either one of those respective engines. If the inlet on the upstream side of the raw water pump is sized for 2" hose, then you need a 2" full flow valve and thru-hull. The same logic applies for the gen-set.

These will be somewhat oversized for safety. If you've ever seen how much water can flow through a 2" hole in the bottom of a boat (and I hope you never do), and compare that to what is coming out of your wet exhaust..... you know that there is much more flow capacity than is actually needed.

But use the correct size anyway.

I ran my 250's and later my 270's with 1 1/2 inlets. No issues.