Vetus Waterlock, an impeller replacement story...

[Capn Jimbo]

I have a freshwater (heat exchanger) cooling system on a Yanmar 30GMF equipped with Vetus 40LP Waterlock. I removed the seawater pump to change the impeller. In doing so, water drained from both the inlet and outlet hose to the pump. After reconnecting the pump I started the engine, got a good initial initial outflow of water from the exhaust, but which stopped. No water in exhaust, immediately stopped engine. Then...

1. Primed the pump's inlet/outlet hoses with water. Still no water in exhaust.

2. Then checked, main seawater throughhull was closed, opened it, still no water in exhaust.

3. Finally disconnected pump, attached a dockside hose to pump's outlet hose and turned on shore water until I saw water exiting from the exhaust. Then reattached seawater pump, primed both inlet/outlet hoses, turned on seawater. Engine started, good water flow, back to normal.

My question: what happened?

I'm guessing that running the engine without the seawater valve open somehow blew the remaining water in the Vetus out the exhaust, and for some reason this did not allow the water pump to work properly until the Vetus was refilled with the dock hose. Apparently the refilling of the Vetus using the dock hose allowed the water pump to work properly. Did I endanger my engine by what I did? It seems to be running fine now. What happened - why didn't the pump work when the Vetus was emptied during my first attempt?

All's well that ends well, but enquiring minds...

[Wotname]

Originally Posted by Capn Jimbo

I have a freshwater (heat exchanger) cooling system on a Yanmar 30GMF equipped with Vetus 40LP Waterlock. I removed the seawater pump to change the impeller. In doing so, water drained from both the inlet and outlet hose to the pump. After reconnecting the pump I started the engine, got a good initial initial outflow of water from the exhaust, but which stopped. No water in exhaust, immediately stopped engine. Then...

1. Primed the pump's inlet/outlet hoses with water. Still no water in exhaust.

2. Then checked, main seawater throughhull was closed, opened it, still no water in exhaust.

3. Finally disconnected pump, attached a dockside hose to pump's outlet hose and turned on shore water until I saw water exiting from the exhaust. Then reattached seawater pump, primed both inlet/outlet hoses, turned on seawater. Engine started, good water flow, back to normal.

My question: what happened?

I'm guessing that running the engine without the seawater valve open somehow blew the remaining water in the Vetus out the exhaust, and for some reason this did not allow the water pump to work properly until the Vetus was refilled with the dock hose. Apparently the refilling of the Vetus using the dock hose allowed the water pump to work properly. Did I endanger my engine by what I did? It seems to be running fine now. What happened - why didn't the pump work when the Vetus was emptied during my first attempt?

All's well that ends well, but enquiring minds...

My guess is different to yours but still it is only a guess.

Clearly the first burst of water was from the water sitting in the Vetus waterlock and that ceased as the seacock was closed.
When you opened the seacock and primed the pump again, I'm sure water entered the watercock but until it filled enough, it would not be blown out of the exhaust. So when you used the dock hose to fill the waterlock, it finally filled enough for the exhaust to force the water out.

I believe the water pump was pumping water as soon as you opened the seacock.

[Alan Mighty]

Capn Jimbo:

Your story resonates with me! I've a Vetus NLP 50 waterlift after my Yanmar 3GM30F. And had a similar experience: changed impeller pump (I carry a spare impeller pump and change the pump rather than just the impeller, then I service the impeller and, if necessary, lip seal) and had a frustrating time of exactly what you reported: no water flow even though everything checked out.

I checked and rechecked the system, starting and aborting the engine multiple times, before everything was back to normal.

I'm now thinking of making a note of the problem and your solution, for next time.

Here's the Vetus (which is I understand now fully owned by Yanmar) diagram of my NLP waterlock: