nuts and bolts

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dom

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I've got a Yanmar 4JH3 and noticed a drip at w/e. It turned out to be from the raw water pump where one of the bolts holding the impeller cover on had spontaneously sheared off. Put a mole grip on as a bodge fix and another bolt head fell off! Took the entire pump off and I've just extracted both studs - Phew!

My somewhat numpty question is this: anyone any idea what replacement bolts I should use in order to avoid any galvanic problems?
 
Doubt it is galvanic action. Anyway, suggest you replace the cover with a Speedseal which uses thumb screws which only need to be hand tight as the cover seals on an O ring.
 
I used knurled thumb screws bought off ebay, cheaper than Speedseal as my cover already has an O ring. Size was M6 from memory but check yours first!
 
My Johnson pump cover is held on by tiny set screws which screw into the pump body. All the pumps I've seen have similar not nuts and bolts. I'm planning to fit a homemade speedseal as they don't make one for my model.
 
ghostlymoron said:
My Johnson pump cover is held on by tiny set screws which screw into the pump body. All the pumps I've seen have similar not nuts and bolts. I'm planning to fit a homemade speedseal as they don't make one for my model.
Click to expand...

Thanks for all of the advice and note to let Sailfree know (BTW yes it's the 75hp version) if appropriate Speedseal exists.

I am particularly interested that nobody (including Tranona) sees a galvanic problem. My initial thought was that the raw water pump is just about the most obvious place for a plentiful supply of electrolyte! But if it was a galvanic issue I would have expected the studs to be difficult to extract and they weren't - which still begs the question why three three bolt heads fell off in succession (one during removal) EVEN though none of the bolt-studs were particularly stiff. I think what I am going to do is reassemble with A2 Stainless bolts (only holding the water pump cap on after all) and then investigate a Speedseal.

As a matter of interest, if I used say A2/4 Stainless bolts in a water pump environment and left them several years would I be wrong to worry about a galvanic problem, even with the considerably less reactive A4 steel?
 
The electrolyte is on the inside and the fixings outside so the water shouldn't come in contact with them. If the pump body is aluminium (which I don't think it is), there could be corrosion in a damp atmosphere but unlikely.
 
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