Detroit Diesel 4-53N raw water pump.

[SDTugs]

Good evening,

I have seemingly been rebuilding my raw water pumps rather often.
We use the boat regularly, 1,000-1,500 miles a year. It seems that I get a weep out of the pump every 5-600 miles.
Has anyone had a good experience with a rebuild kit, or a replacement for the Jabsco pump.

 

[Lepke]

Is your raw water pump gear driven or belt driven?
It sounds like there too much side pressure as if a belt is too tight or a gear driven pump isn't properly in contact with the engine gear. Bearings get worn from side pressure and then the seal starts to go.
I have twin 671s, and the pumps last almost forever. Current pumps are 12 years past an overhaul. Prior to covid I was doing 5,000+ NM a year. Impellers are the only item I replace routinely.
I carry replacement pumps but never had to use them. You might pick up a spare. Usually used pumps on ebay. You could send your pump to Depco along with the history. They might find a slightly bent shaft or a miscast housing. I've been rebuilding my pumps since the 1960s. Usually a internal problem stands out.

 

[SDTugs]

Is your raw water pump gear driven or belt driven?
It sounds like there too much side pressure as if a belt is too tight or a gear driven pump isn't properly in contact with the engine gear. Bearings get worn from side pressure and then the seal starts to go.
I have twin 671s, and the pumps last almost forever. Current pumps are 12 years past an overhaul. Prior to covid I was doing 5,000+ NM a year. Impellers are the only item I replace routinely.
I carry replacement pumps but never had to use them. You might pick up a spare. Usually used pumps on ebay. You could send your pump to Depco along with the history. They might find a slightly bent shaft or a miscast housing. I've been rebuilding my pumps since the 1960s. Usually an internal problem stands out.

Interesting. Mine are gear driven. There is a 3 bolt flange that mates directly with the aft end of the block. Not exactly sure how the alignment would be off.
Both the oil side and the wet side are lip seals. The wet side lip seal is always the one that fails. Next time I rebuild one I’ll have to take a look at the shaft and see if there are any obvious signs of wear.
I have spare pumps and swap so I can rebuild at my leisure. Might have to send one to Depco and see if they have any ideas. I have been just rebuilding them myself.

 

[Taras]

I have not rebuilt that particular pump but just wondering if the bearing requires to be packed with grease prior to installation?

 

[SDTugs]

I have not rebuilt that particular pump but just wondering if the bearing requires to be packed with grease prior to installation?

I have never looked for a rebuild procedure. That could be a missing step. Usually I pull the pump, pop of the impeller, pull the shaft, check the bearing, and slap new lip seals.

 

[Tired Trawler]

Greetings!
Is the impeller shaft deeply scored where the seal lip rides?
Can the seals be repositioned to an unworn area of the shaft?
Are you polishing the shaft seal area with extremely fine emery tape?
Are you lubricating the seals & shaft with silicone grease formulated for rubber?
Are you using the correct lip seals with stainless steel or bronze garter springs?
Do the seal bodies have exposed steel not covered by rubber?
Are you protecting the seal lips during installation by wrapping a single layer of black plastic electrical tape over any sharp splines?
Are you installing the new seals squarely in the pump housing?
Hope these thoughts help,
Good Luck!