Should raw water pump be smooth inside?

[HappieHippie]

Hi all, I have a water pump">raw water pump that I bought used, and upon taking the cover off, the impeller cavity is very rough inside and the little ramp piece is especially rough, and that looks like it was cast that way. Wouldnt it eat the impeller like that?

Also if anyone knows what pump this is, it supposedly came from a Yanmar but I cant find a similar one. I can ask about that on a Yanmar forum though.

Any advice appreciated!

[Simi 60]

Oh dear.

Bin job I reckon.

[MartinR]

Repaired with chemical metal? You are right, should be smooth.

[Lepke]

Looks like a build up, maybe melted impeller or gasket cement.

[RaymondR]

Give it a good going over with some 120 grit sand paper and it will be fine. The pits won't bother the rubber impeller because it is a fairly low pressure device and the ends of the impellers get dragged over the circumferential surfaces.

[GordMay]

Greetings and welcome aboard the CF, Happy.

[jimbunyard]

Yeah, just clean it up with 120 (or finer) sandpaper and give it a shot. The cam looks pretty bad though, if it doesn't pump adequately, replacement cams are available separately, if you're in the US or close, Depco Pumps is a good knowledgeable supplier.

[Emmalina]

120 and a rebuild kit and it should be fine !

[jooa]

That the same water pump i have on my 1977 Yanmar YSE 8. Inside should be smooth, but like the other guys have said try cleaning up with a fine sandpaper and see what happens.

[jharding]

soak it in vinegar and salt, nobody could tell me how much salt so I just dumped in a fair amount, next day all looked like new. you need to pay attention to the side plates also.

[RaymondR]

On a previous boat I had a Yanmar 3GM30 for which I needed a replacement raw water pump. In Australia I was quoted in excess of $800 for it. When I reproached the dealer for the excessive cost he said that whilst the pump might look like a standard Johnston pump and use many of the same parts it was manufactured specifically for Yanmar engines hence the high cost.

I went and bought the same pump with a standard mounting foot from a chandlery, made a mounting plate from a piece of alloy angle and got out of the repair for about $240. And, since the Yanmar plate was steel and I'd have to take the pump off, clean of the rust and repaint it I no longer had to do it with the alloy.