Raw water pump on AQ255

"I'm completing an engine

"I'm completing an engine rebuild. When I started it the first time, with a flush device on I/O that I've used many times, engine quickly overheated. Shut down and found risers dry and rubber exhaust tubes smoking. Engine registered 190 when I shut down after 3-4 min. running. Checked everything re plugged lines etc, and all ok. Pulled outlet hose of raw water pump and impeller looked good and would push water when I filled inlet line and turned pump by hand. THEN I discovered I'd never tightened the pulley bolts! However, when reassembled and cranked engine w/ coil wire off, it wouldn't pump any water. Don't really want to risk starting it again and overheating it. So my question is (yeh, finally) should the raw water pump draw water up from I/O flush device and into engine when only cranking?"

"Yes, provided there is no sou

"Yes, provided there is no source of air ingress on the suction side. Have you checked the condition of the raw water hose connector in the outdrive? They get corroded with time, and if they become perforated the pump will suck air rather than water."

"Thank you. The connector loo

"Thank you. The connector looked ok when I had the upper gear housing off, tho I didn't really inspect it. Hose was kinda old, but I didn't replace it. I'll look for air leak, but I'm really baffled."

"Put a 5 galpail in the boat a

"Put a 5 galpail in the boat and fill the pail with water. Disconnect the water hose from the inlet of the water pump at the transom.
Stick this hose in the pail.

Start engine. You should get water out of the exhaust quite soon (seconds) after starting the engine.
If you do.. the problem is between the transom and the end of the drive.
If you don't get water, then the problem is between the end of that hose and....

The engine won't be running long enough to overheat it."

"I did some work on Bruce'

"I did some work on Bruce's drive some time back and just now spoke with him.
He is using one of the "run-dry" impellers.
I've not used any of these since reading about them loosing the bond between hub and impeller after a short while! Not good!

I suggested that he pull this and replace with a standard Sherwood impeller (this is the old AQ 200/255 B style belt driven sea water pump by Sherwood).

Also suggested that he re-examine the water neck fitting and special beaded gasket. I find that these can often be a source of an air leak.
Suction leaks, as you know, can be tricky to locate.

His engine is new... still needs flat tappet cam follower break-in.

Also suggested that he inspect the bellows flapper (280 w/ no outlet flapper) and both side rubber exhaust couplers since this got hot! (he smelled burning rubber)

This is raw water cooled.... has modified exhaust system (no longer the 1 pc manifolds) all else appears to be typical Volvo Penta.

Any other suggestions?

."

"Thank you Robert and Rick. W

"Thank you Robert and Rick. Will start by replacing that dry-run impeller, then test suction within the bilge and go from there. As I've said before, this forum sure is a great resource for people like me with limited mechanical skills/experience/$."