I've done this a thousand times with outboards, as The hose water just spills around the "muffs". Some even have hose fittings.
However, I dislike running the diesel on the hard, particularly if you're up on stands. The vibration worries me for starters
. If you pressurize a hose into some diesel raw water cooling intakes, you very well may flood the cylinders. Trying to draw from a bucket is a good solution, but you need a space where bucket overflow and exhaust
discharge can freely spill to the ground. Oily, diesel exhaust
can be messy, albeit you are also pumping it into the water during the season. Finally, if you're drawing from a bucket, it most likely needs to be very close to the level of the hull intake. Your pump
may not have he lift to get it up from the ground.
I do winter work, close all seacocks, and test after launch.