I'm posting this for any advice or comments that may help
Here's the set up on a 57ft narrowboat
It's a JP2 industrial engine with a marine fresh water centrifugal pump cooling from a skin tank. Calorifier fed from out feed from pump and return before a thermostat (72°C)
Lots of domestic hot water but output from engine only gets to 60°C max and return from skin tank 40°C
End plate on water pump has a felt seal, this is sealed by a grease cup using waterproof grease
I continuously have problems with leaks from the felt seal to which I've replaced numerous times, grease just pouring through seal, my thoughts on this being the continuous pressure from pump not being able to circulate around system
I've decided to go for a proper bearing type seal, in which I've had the end plate outer lip cut out to fit a 42mm x 28mm x 7m seal
I will post pics soon just am having phone issues!