Jabsco thumb screws

single

single

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What thread are these screws that hold the cover plate on the Jabsco raw water pumps? (its about 10 yrs old)
Also is there anywhere that i can get x8 knurled thumb screws without paying the silly price from Speedseal?

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old ones are m4 you can buy stainless m4 cap heads then get the knurled thumb screws from rs press em on job done
 
I don't know what you're planning to do but thumb screws won't provide enough compression to provide a leak proof seal with a paper gasket I'm told.
 
I use M4 socket head screws as I can't get a screwdriver to fit between the screw and the starter motor. Works a treat!
 
single said:
Maybe thats why speedseal use the o ring seal?
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No. The o ring is to facilitate easy removal and replacement. Poor sealing with a paper gasket is one of the potential problems which the Speedseal solves. when you have had to change an impeller in a lumpy sea you will appreciate why the Speedseal is a good investment - particularly if you have dropped one of those 6 fiddly little screws in the bilge!
 
ghostlymoron said:
Exacerly! I got a friend to cut a groove and fit an O ring.
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That's the best solution yet!
Personal experience is that a lot of these wretched pumps have left-hand-drive threads: something like UNF or ASF or one of those infernal standards that confound civilised, metric, right-hand drive folks!
Run an oversize metric tap through- M4 or 5 is easier to get than Yanqui, and even our local supplier sells metric wing-bolts in SS, so you can get a decent torque on the screws, especially if it's a 3-screw cover.
 
I ended up buying the 'Speedseal Life' and what a great bit of engineering. Great service and quick delivery. Highly recommended.
 
Some of the smaller pumps have (had?) a UNF thread like 8-32. A long time ago I bought a length of SS threaded rod, cut short lengths of it to make studs that I later Loctited into the threads on the pump body. This allowed me to hang the cover plate in place before fiddling with the nuts. Having a lathe I turned and tapped some large diameter knurled nuts to suit. Never had a leak. I had intended to make a new cover plate with an O-ring but I sold the boat before I got round to doing it.
 
PuffTheMagicDragon said:
Some of the smaller pumps have (had?) a UNF thread like 8-32. A long time ago I bought a length of SS threaded rod, cut short lengths of it to make studs that I later Loctited into the threads on the pump body. This allowed me to hang the cover plate in place before fiddling with the nuts. Having a lathe I turned and tapped some large diameter knurled nuts to suit. Never had a leak. I had intended to make a new cover plate with an O-ring but I sold the boat before I got round to doing it.
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Like mine, that is UNF.
View attachment 52074
 
I got 3 Knurled SS thumb screws from ebay a few months ago, from memory M6, but I did check with a known screw beforehand. Johnson pump on a Beta 25hp. Paid about £10 from memory. Seem to work fine, screws greased before fitting and can be removed without tools. The face plate does have an O ring on the face.
 
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