For the first two years, or 600 engine hours, of cruising on BCC28 #116 Zygote, we felt secure that we had two spare impellers for the raw water coolant pump aboard. We had, after all, ordered the spares, including gaskets for the cover plate of the pump, from an authorised Yanmar USA retailer.
At around 500 engine hours, a fellow BCC28 skipper told me that he also carries a complete spare coolant pump, arguing that swapping pumps is faster (and more redundant and so perhaps a little more secure) than swapping impellers.
At 610 engine hours, I pulled the raw water coolant pump. And discovered that our spare impellers would have done nothing but generate frustration.
Story is that our stock standard Yanmar 3GM30F was equipped with a pump from Johnson Pump AB in Sweden.
The pump is so labelled and carries the further detail, F4B-903 10-24509-09, imprinted on its impeller cover plate. This pump has an O-ring, not a gasket, and uses Johnson 810 slotted-shaft through-pin impellers. The cover plate also has arrows showing two directions of rotation: the lighter imprint is correct. The cover plate is held in place by hex-head bolts.
The spare impellers I had bought in the USA were key-drive impellers.
I checked my spare water coolant pump (bought from Yanmar Singapore). This pump has a cast bronze body imprinted with the identifiers K W 01K-19. And this
pump uses a Yanmar 145410-46110 gasket on the pump cover and key-drive impellers, same as what Yanmar USA had supplied me as part number 128296-42070. The cover plate is held in place by slot-head bolts.
I’m in the process of buying some slotted-shaft through-pin impellers. After 610 engine hours, my original impeller had a crack in one of the vanes.
The attached impellers.jpg (about 55 K) shows the variety of impellers, with a key to standard terminology.
Cheers
Bil