[Glenn Diver]

This year I purchased a 190 Bay and a new Yamaha 150 4-stroke outboard. This is the first outboard I've owned. I use the boat in salt water. The manual says to flush the cooling system after use, which I always do, but the manual says nothing of rinsing the motor itself. My question: How frequently should I remove the Yamaha's engine cover, and rinse off the surfaces of the engine itself? Does it make any difference in reliability or longevity if I rinse under the hood or just leave the engine cover on?
Thanks,
Glenn in Florida