Did it for years on a twin engine sportfish with no problems. Install the tee fitting with a hose bibb between your thru hull
, or strainer, and raw water pump
. Use an old washing
machine hose to make the final connection.
Do not close the thru hull
when first starting the engine, and measure garden hose delivery
(gallons per minute) so you have an idea of how much flow to allow thru the hose into your raw water supply so it matches your normal exhaust
water flow. Be CAREFUL to not over-pressure your raw water system. I always left the garden hose connection loose so some fresh water flowed into the bilge
, wrap a rag around it so it doesnt spray over the engine but still lets you know you have flow.
Run for several minutes to ensure your engine thermostats open. Shut down engine, let fresh water run another 30 seconds then 1. shut off fresh water garden hose 2. Close hose bibb and finally 3. close the thru hull.
You will trap enough fresh water in your thru hull valve and raw water strainer. Leave the ignition key hanging on the thru hull so you dont start without opening.