We run a 500 Hp diesel on the hard
all the time.
Can you close the main raw water
intake valve between the strainer and the thru hull
If yes, then close the valve and open the top of your sea strainer and let the hose run into that. Your pump will pull the water from there.
Do not physically attach the garden hose to your raw water intake line. That could cause damage if the engine
isn't running and the city water pressure is high.
Keep an eye on the sea strainer so it always has water. Make sure you don't rev the engine
too much as that could pull the water faster than it can be delivered.
By running water into the sea strainer it will just overflow into the bilge
when the engine is shut off and not over overcome your raw water pump