volvo diesel raw water impellers

[freeportblue]

My neighbor has a twin engine boat with volvo 41A's. We replaced the raw water impellers with new johnson impellers that appear exactly the same as the old impellers ( Jabso I believe). Neither pump will prime and pump. Relplaced the new impeller with the old one and both worked fine. Anyone else experienced this? Are ther differences in impeller material that I should be concerned with such as neopreme vs. Nitrile?

Thanks
Billy

[Don S]

The diameter might be the same and the number of vanes might be the same, but is the height of the impeller the same?

[freeportblue]

The diameter might be the same and the number of vanes might be the same, but is the height of the impeller the same?

Don
As far as we can tell it is exactly the same and Johnson lists it as the replacement. I have the exact same engine in my boat and I am running the Johnson impeller also and my engine is running warmer than I would perfer. I have just completely rebuilt my engine and serviced the cooling system to include thermonstats,circulation pump,cleaned all exchangers etc. If I can put a gauge in the raw water system what pressure should it read?

Thanks
Billy

[Don S]

I have no idea what the pressures run, but I can tell you one thing. If my engine ran hotter with a johnson impeller than it did with a Volvo impeller and another persons engines wouldn't pump at all with a johnson impeller. I would personally stop using Johnson impellers and get the right ones. Obviously there is a problem some where.