How important is the gasket thickness?

[TSB240]

I have just purchased a replacement impeller and gasket for our water pump.

Included in the kit is a paper gasket seal for the outer cover which seems to be made from very thin material. It is likely to need replacing anytime you want to inspect the impeller as it is so fragile.

I have some slightly thicker gasket paper that I had for making up gaskets for various home built 2 stroke engines, which use non standard modified carbs and mounts. This paper is very slightly thicker but feels to have a bit of "give" in it?

I imagine there is a bit of tolerance with the end seals of the impeller that might allow a slightly thicker spare to be used?

I assume that I could run the engine up for a short period and see if it pumps water with a thicker gasket installed

Anybody else make their own spare water pump gaskets?

 

[sailorman]

there is a reason for a gasket of the thickness supplied, to keep the chamber depth/ impeller a snug fit to stop water bypass under pressure

 

[rob2]

I've often wondered this, too. Luckily, the gasket on my pump is stuck fast to the pump body so I leave it there and smear it with grease before refitting the plate. There must be a tolerance for the gasket, though as many pumps have more significant wear in the plate which can be expected to allow bypass, yet function effectively enough...

Rob.

 

[sailorman]

I've often wondered this, too. Luckily, the gasket on my pump is stuck fast to the pump body so I leave it there and smear it with grease before refitting the plate. There must be a tolerance for the gasket, though as many pumps have more significant wear in the plate which can be expected to allow bypass, yet function effectively enough...

Rob.

never forget the "wear plate" thats a service item

 

[DownWest]

Had a problem with an O/B. Looked OK but was not pumping well. New impeller sorted it. So, small differences in the end clearance can be important.

 

[thalassa]

Anybody else make their own spare water pump gaskets?

The gasket that came with my new Jabsco 22779-0001 impeller had a thickness of 0.32 mm. However, after only 8 hours of use, the exhaust water produced seemed less than normal. After taking the pump off and removing the cover, it turned out that two blades had sheared off. Luckily, they were still in the pump. The rubber showed no cracking -so it hadn't been sitting on the chandlers' shelf since the dawn of time.
It might be possible that the gasket was indeed too thin, compressing and deforming the vanes slightly. But as SM says, too thick a gasket and you lose pressure. So, yes I consider the thickness critical.
I now use Ebay replacement impellers which come without gaskets, and make my own from Photo paper with a thickness of 0.37 mm. After scanning and duplicating with Photoshop, I've printed out the gasket page. They are a precise fit. I first drill the holes using the cover as a guide, and then cut out the center. Scissors take care of the rest. After mounting with some grease, I test the rotation. Too easy, gasket too thick. Lots of drag, gasket too tight.