Raw Water impeller questions

[Mike Brown]

I have a 1981 Hunter 27, with the Renault RC8D diesel.
I recently had an overheating situation, and determined that I had no raw water going through the cooling system. I ruled out a blockage of the intake, as I have water flowing to the water pump. When running for a short time, I removed the outflow hose from the pump, and saw that the pump was not discharging water. I removed the housing from the pump to inspect the impeller. I have attached a picture of the impeller in the housing. Here are my questions:
1. The impeller looks like it is in pretty good shape. Do they fail and still look this good?
2. In the picture, the water inlet is at the bottom right, and the outlet at the top right. To me it looks like the impeller should rotate in a counter-clockwise direction. However, the belt rotates it in a clockwise direction. Are the fins going the wrong way? what direction should the impeller rotate?
3. The scoring in the housing looks concerning. Is this anything to worry about?
4. There is no gasket or O-ring in between the housing and the cover. (it has never leaked). Is that correct?

Thanks for any info!

 

[ggrizzard]

Sometimes the impeller will fail by the rubber part spinning freely on the brass hub. So, the hub spins on the shaft but the vanes stay put and no water is pumped.

 

[Skipper]

1. Yes.
2. Looks backwards.
3. Yes. Should be smooth. Although the grooves look evenly spaced. Which pump brand is it?
4. Well-fit parts may be fine with no gasket. Putting a gasket won't hurt it.

 

[markwbird]

I do not see how it could be spinning the wrong way. Not really possible. This type of pump requires a really good seal on the side walls of the impeller to develop the suction it needs to draw water up. That may be it. Also, the missing gasket may be contributing to the suction issue. If the side walls are heavily scored it may be leaking suction. One trick is to turn the cover plate around so the outside is on the inside. This presents an unscored, smooth surface for the impeller to seal against. If the seal is the problem you should also replace the impeller.

 

[Mike Brown]

So, it sounds like the impeller should travel clockwise, but the canes are the wrong direction in the pic. It’s possible that I moved the belt in the opposite direction, causing the vanes to flip the other way. Presumably they would flip back when the belt was going the right way.
Not sure of the make of the pump. It is original equipment with the Renault.

 

[Mike Brown]

Mark Bird: I have an impeller on order and should have it at the end of this week. Oddly, the inside of the cover is perfectly smooth. It’s just the inside of the housing that is scored. This seemed to be a sudden problem, which lends credence to the idea that the impeller has broken loose from the hub. I am hoping a new impeller will solve it.

 

[Johnb]

I have a 1981 Hunter 27, with the Renault RC8D diesel.

2. In the picture, the water inlet is at the bottom right, and the outlet at the top right. To me it looks like the impeller should rotate in a counter-clockwise direction. However, the belt rotates it in a clockwise direction. Are the fins going the wrong way? what direction should the impeller rotate?
Thanks for any info!

Looking at your picture the vanes are squeezed down at the bottom right and "unsqueezed" at the top right. These pumps work by "sucking" in at a larger volume and then pushing the water out by squeezing the vanes down as they rotate toward the pump outlet. That would put the inlet at the top right and the outlet at the bottom right - opposite of what you state above.

Has the pump been off? Is it possible it has been re assembled backwards? Is the picture maybe somehow inverted? Are the hoses connected to the right ports?

 

[markwbird]

Maybe it sucked something in that scored the walls. Shell or grit from the bottom. Did you ground the boat in sand and then rev the engine to get off?

 

[Mike Brown]

No grounding, but there was a lot of wood debris from recent rains. (Tennessee lake sailing) I first thought that maybe something had lodged in the intake, but it is not blocked.

 

[Mike Brown]

Just to update: I received the replacement impeller from France, only to discover that the shaft in the pump had been changed out to accommodate a Jabsco impeller. Ordered one of those, installed it, and it appears to be moving water out the exhaust.