Cam and Set Screw Gone Pink - Jabsco Raw Water Pump

rardiH36

rardiH36

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Jun 21, 2007
2,106
Hunter Cherubini 36_80-82 Sausalito / San Francisco Bay
Raw water circulation for my old Yanmar is done by a belt driven small Jabsco pump. Model 2760-0003 to be exact.

I replaced my original pump with a new one 2.5 years ago. Only 150 running hours since. Last week, I noticed the pump leaking. Removing it for inspection, I first checked the bronze (or maybe it is brass) set screw for the pump's cam piece. With hardly any twist at all on it, the set screw simply sheared off. Upon taking off the pump cover plate and removing the impeller, I discovered the set screw had turned pink and brittle. Fortunately the broken segment still inside the cam extracted easily when I drilled through the center with a 1/16" bit. The cam itself is still good yellow metal.

Then I decided to take a look at the cam from my old pump which I had kept around. It is very pink looking. And actually I broke piece off of it with just a light poke at it with a screwdriver.

Is this a common occurance with these pumps?

For now, I have replaced the corroded pink set screw with an SS screw.

Will I be setting up even faster electrolysis due to disimilar metals?

Thanks for any insights.
 
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Charles Erwin

Charles Erwin

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Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Good choice actually. The screws/cam you see failing have a high zinc content in their recipe hence the decay. The new screw is probably 304 thus the more noble. But no matter because the part of the screw exposed to seawater (just the tip) is very small compared to the pump body. Don't forget to put some sealant (like permatex # 2 ) on the screw threads . You can also paint the end of the screw with nail polish or similar if you want.

Charles
 
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rardiH36

rardiH36

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Jun 21, 2007
2,106
Hunter Cherubini 36_80-82 Sausalito / San Francisco Bay
Charles:

Many thanks. Yes, I did use Permatex sealant on the SS screw threads and around the head. Plus a good dab on the cam itself so that the compound might be forced up into the pump body. And also maybe the sealant will provide some electrical isolation between the cam and the pump body. I while had the pump apart, I replaced the water-side lip seal and the O-ring as well. Hope I got the leak problem fixed! I will be remounting it this afternoon.

But still its worrying about the de-zincing after such a short period.
 
Charles Erwin

Charles Erwin

.
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Do not despair - this is an opportunity. You have a fresh assembly and so can observe how this new combination performs. I am betting there will not be any decay but let us know what happens.

Charles

p.s. Verify no sealant can migrate into the contact surfaces - impeller to pump body.
 
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