Kirby, forgot one thing until you get the raw water situation clear I would recommend the following steps before starting the engine in your normal way.I do have an optical reader on order and it should be here later this week,I was just calling it a tach because I was thinking in terms of a electronic tachometer.James
1. SHUT-OFF your seacock for raw water intake.
2. Start your engine
3. OPEN the seacock and check for water going out the exhaust.
this will prevent water from backing up into the exhaust system and causing big damage.
I would also recommend a new raw water impeller. It's a blue one that's called a RUN-DRY! it allows you to run up to 15-20 minutes of running with no or little water flow.
I have been using the Globe Blue Run-Dry™ Impellers for years and I have been very happy with them. I usually check them at the end of the season and they look almost new with a little discoloration.