7.5 Mercury water flow issues

I am working on a friend's 7.5 Mercury. He said it wouldn't start but it did for me on the 3rd pull. What concerns me most at the moment is that no water is exiting the tell tale. I pulled the LU and checked the impeller. It's new and is turning with the shaft. I put the cover back on and ran spun the shaft with a drill. Pumping water fine.

Nothing I tried gets any water through to the telltale hose. I have it unplugged at the top of #1 and no water is reaching that elbow. I connected a hose to the copper pipe. I blew air through it. Nothing.

The only thing that comes out of the elbow at the top of the engine seems to be exhaust.

Warm water will flow out the "flush" plug hole with the motor running so I do believe the water pump is moving some water.

Adapt the garden hose to the water tube and see if you can get water out of the telltale elbow? Short of pulling the powerhead you may be able to unplug the blockage with saltaway in a barrel of water. Has the motor been flushed regularly after each use? Lake and river water has alot of silt and minerals in it as well. The saltaway will dissolve the corrosion and crap in the motor as long as there is flow through the circuits. are you running it in a barrel of water? do not use the flush port when the engine is running you will fry the impeller. What could be happening is the exhaust pressure is higher than water pressure due to a restriction you may need to pull the powerhead and install a new gasket between the adaptor plate and the block.

I attached a garden hose to the copper pipe and could not get any water from the elbow but water would flow out of the flush port. I attached the hose to the elbow and water came out the copper pipe, the flush port, and exhaust.

Could it be a blown head gasket? But, it seems like water would flow out the elbow as long as the engine isn't running.

You may have cleared the blockage did you attach it to the water tube again after you backflushed it with the elbow it should flow easy in both directions?

Was the old impeller broken up into pieces if so you likely have a chunk of rubber throwing you fits, sometimes high pressure air will clear it out but you also risk it clogging somewhere else down stream there is no head gasket just a gasket for the water jacket cover.

Yes, if I remember correctly I had to fish pieces of the old impeller out with a piece of wire. All of the vanes were broken off.

You need to back flush it with water and compressed air. Blow it right into the Tell Tale port with the power head off.

Jeff

Just curious, but how does the exhaust enter into the cooling system?

Ok. Another project. LOL

The cooling enters the exhaust after it goes through the head and the exhaust cover. If exhaust gets into the cooling system it is because of low or no water pressure.

Backflushed with water then compressed air like you guys instructed. When it hit the lever on my air gun I should have stood out of the way. The obstruction was blown out along with a considerable amount of water. I was really happy and excited but it only LOOKED LIKE I peed myself, I didn't really. Standing in the wrong place at the wrong time.

As far as it not running, the only thing I could find was the slow speed adjustment was turned out about 6 or 7 turns. I have no idea how it got in that position. No way it would idle like that. I removed the carb and cleaned it again just because and it is running great again. Thanks for the help.