No water coming out

[Calif. Ted]

John, no place for air lock in elbow or muffler, hose feeds water under pressure from pump. The inside passages of the elbow can be fairly small and with metals, seawater and diesel exhaust all mixing at high temps you couldn't create better conditions for rust, et al. Pretty much just dumps the seawater stream into the exhaust where the elbow turns down.
If you have more than a couple hundred hours on the engine without changing the elbow it's probably clogged, running for short periods and at an idle most of the time will clog things faster.
The exhaust side creates a kind of "coke" that is very hard.

 

[John]

shaft key

The shaft key might be the problem....even though it pumps water it might be spinning without the key but not fast enough for the whole run

I'll check that.

From the responses, I take it that some sort of air lock, caused by the water emptying out of the muffler and/or the mixing elbow is not really possible.

 

[capjules]

is the engine overheating while this episode of no water is coming out ?

if the enine is overheating then you have a blockage somewhere, if
the engine is not overheating then water flow is normal but you have a hole in a hose or muffler that is letting the water exit the path and flow into the blige instead of out the exhaust with the exhaust gasses.

do you smell any exhaust in the boat during this problem ??

 

[SEMIJim]

From the responses, I take it that some sort of air lock, caused by the water emptying out of the muffler and/or the mixing elbow is not really possible.

It's no more possible than air lock in your garden hose preventing water coming out when your turn on the tap

I believe you verified your pump is pumping, yes? And that raw water is flowing thru the heat exchanger, yes? All that's left is a blockage downstream of the raw water output of your heat exchanger. My understanding of how that system works is that the raw water proceeds from the heat exchanger, via a hose to the mixing elbow, thence to the water lift muffler, and out of the boat.

My guess is that the last time you snaked-out the "hose" you actually broke-loose an obstruction in the mixing elbow. Sounds like it's time, perhaps past time, for a new mixing elbow.

Btw: You can't snake things out from the aft end of things. Go research how your water lift exhaust works and you'll see why. Besides: If you're getting exhaust gases out, it's not blocked aft of the water lift muffler.

Jim

 

[John]

I'm thinking that the impeller is slipping a bit, not so much that it won't pump at all though. This would explain why some water is being pumped, but maybe not enough to pump it all the way through. It's probably time to change the mixing elbow, which has never been changed to my knowledge. (I'm the third owner, and the engine presently has some 750 hours on it.) But I still suspect that the present problem has something to do with what I just did - change the impeller rather than when I snaked the hose out before; that was about a year ago and there weren't any problems since then until now. So I can't help but suspect that the problem is caused by something that happened when I changed the impeller. I'm going to check that this morning.

 

[John]

How to turn a 1/2 job into a 3 hour one

So I was right that the problem was insufficient pressure.

First I took all hoses apart, snaking out many of them, taking the pump apart (at least twice), going through everything over and over... It's clear that the pump was pumping water through the heat exchange, except I had the feeling it wasn't with enough pressure. Part of the reason it took me so long was that I'm really not that familiar with the cooling system and didn't know where all the hoses went. The hose that carries the water from the HX to the mixing elbow first goes up to just under the deck and through a siphon break. Water was going into the hose, but with insufficient pressure to get all the way up to the top. I took apart the pump again. There was a thin layer (maybe 1/64 inch thick if that) of crud built up in a ring on the back plate of the pump - behind the impeller - just behind the outer edge of the fins of it. I scraped that off, and the problem was solved.

Thanks to everybody for their suggestions.

 

[zeehag]

hooooyaahhh!!!!!! congratultions!!!! glad it was simple!!!!

 

[SEMIJim]

Glad you figured it out and got it going!

FWIW: When you wrote "there was water coming out," I assumed you meant something that looked like a "reasonable" volume. That's what I get for assuming

Jim

 

[John]

I thought so too

Glad you figured it out and got it going!

FWIW: When you wrote "there was water coming out," I assumed you meant something that looked like a "reasonable" volume. That's what I get for assuming

Jim

I've never had the hoses off with the motor running, so I didn't know what volume to expect.

 

[SEMIJim]

I've never had the hoses off with the motor running, so I didn't know what volume to expect.

Understood. I'm pointing the finger at me, for assuming something I shouldn't have, not at you

Jim

 

[petersea]

When u say you have water out the heat exchanger do u reallly mean the heat exchnager or the exhaust from the mixing elbow ? ??? Did you remove any of the exhaust parts ??? Is the water coming out of the elbow or just the hose that feeds the elbow ??? IF u have water out the elbow your blockage is somewhere in the hose or muffler .