On, Isle of Wight, we would often have a problem with the Jabsco plunger screeching and being difficult to pump. It just so happens that when the boat was delivered, we found a crack in the pump housing and Catalina sent us a new pump to us for replacement of the defective one.
The maintenance instructions in the manual with the new pump, noted that the proper lubrication for the pump plunger was petroleum jelly (Vaseline). Some owners never get around to reading the manuals that come with the boat, but with a replacement part its difficult not to. So every time the pump leather got dry and difficult to pump, we dutifully removed the pump plunger to lubricate it. To do this remove the 6 screws that hold the top of the assembly to the pump body. Carefully remove it to save the gasket and the rubber flapper valves that switch from “”Flush” to “Dry”. When removing the top assembly note the position of the rubber flapper valves so they will be correctly positioned when the top assembly is replaced.
We have lubricated that pump several times. We removed the plunger. Smeared the inside of the pump body with Vaseline above and below the plunger, and replaced the pump top tightening the screws. And the pump always worked so smoothly we wondered why we always waited too long to relube the plunger. However the last time we did the miracle cure we over tightened one of the screws. These screws fit into raised bosses on the pump body. In over tightening the screw, one of the bosses broke off of the pump body and it was impossible to get the seal necessary for the pump to work.
So the moral of the story is, if you want an easy operating Jabsco head pump, lubricate it with petroleum jelly. Note: be careful not to over tighten the gasket screws for fear of popping the screw bosses from the pump body because it will require a new body assembly. The cost was approximately $115 when we replaced it and it is kind of messy and stinky. This might also be a good time to replace the JOKER valve if you have to replace the pump assembly. Sometimes you can catch one of these heads on sale for about the same price.
Webmaster Note: West Marine sells a liquid product called “Head Lube”. A splash of this in the bowl with one pump when leaving the boat works well also. When winterizing, RV antifreeze does a nice job of keeping the plunger flexible and the system pumping smoothly.