A 47 bhp engine will produce 120mbh of energy. A diesel
engine is roughly 50% efficient so roughly 50% of the energy is wasted as heat, the other 50 percent is converted to motive power. So about 60MBH is heat to the walls. That at 20 degree delta
would require 6 gpm.
Even if the whole amount of energy was wasted as heat and allowing it all to the engine walls, it's still only 12 gpm at 20 degree delta
. That's probably a low delta. I suspect most engines are running 30-40 degrees delta on raw water
, based on hose temperatures prior to the mixing elbow
Even at 12 gpm, a 1" diameter hose will have about 2.1 feet of head
loss per 10 feet of hose length. That is very doable for a 1" hose and is not excessive at all.
So short answer a 1" hose will be fine from a flow rate standpoint. Assuming you have less then 10 feet of hose total to the pump and heat exchanger
and aft loop.
So run 1-1/4" hose to the discharge of the seastrainer as reduce down to the 1" port connection. BTW hard pipe pressure drop is much less then hose. Partly due to the soft rubber liner that has a higher friction coefficient then smooth metal pipe.
If you have a 1" full port seacock, your probably good. If you had a long run of hose (more then 15-20 feet total for all hose used) then changing out the seacock to 1-1/4" would be safe. For the typical short run it's probably not an issue.
One issue with a 1" seacock is you would want to make sure the seacock had little hard growth. To many critters at the seacock would reduce the flow rate, or rather increase the pressure drop. That would be one reason to install a 1-1/4" seacock as it give you a bit of a safety