No raw water flow thru exhaust

[seaduct]

We went on our shakedown of the season today in our 1986 catalina 30. All was good until we dropped the sails, started the engine to return to the marina. I didn't get any water flow out of the muffler. I had just changed the impeller prior to starting the season. On the way out today water was flowing fine. Probably only about 40 minutes run time. At any rate I shut things down when i noticed lack of water on the re-start. It had probably been running a minute or two. I inspected the impeller (which was fine), pulled the inlet end off the hx (which seemed clear), pulled the pencil zinc at the exit end of the hex (which seemed fine). Also water seems to be flowing ok thru the strainer and up thru the pump and into the hx. So..I guess I have a block somewhere between the hx and exhaust or... Maybe the pump just isn't pumping. Oh yes, I also carefully confirm that the pump is turning (my wife cranked it for a split second while I looked at the impeller with the cover off).

Any one else ever encounter this mystery or have ideas for me to check?

 

[Sanfelice]

Possibly an air lock in your system. If you have the Unversal diesel, try loosening the cover in front of the pump (the impellor cover) crank the engine a few times and tighten the cover back up. This is called burping.

 

[seaduct]

I did that (my pump has a vent plug at the top). Water is definitely getting to that point. Still not flowing once I start the engine.

 

[Sailvayu]

9 times out of 10 when there is a blockage it is where the water is injected into the exhaust elbow. Pull the hose there and check for water flow. If you have water the blockage is there, if not work your way back. good luck.

 

[Chris Burti]

Also...check the water pump cover plate. If there is any scoring on the impeller side surface, it will not pump water even with a new impeller.

 

[Brad Woodward]

You may also have a blockage in the heat exchanger. I had a problem with my 86 last month. It would over heat above 20K. Took the ends off the HX and it had some deposits on it but I could see through it OK. Finally took it off and found the exit for the salt water side was 99% plugged. I couldn't believe it wasn't overheating all the time. Just a pinhole was letting the water through. The rest of the hoses and HX were not bad at all. Bought some HCL acid at the store, poured it through the HX until it was clean, reinstalled, and I now can run my engine at 30k without overheating. A week later I found the bolt that holds the alternator tight in my bilge, but that is another long story.

 

[Old Skool Neil]

What brand of pump are we talking about?