Transom shield mounting bolt failures

"Hi Guys,
Lately I have heard

"Hi Guys,
Lately I have heard of several transom shield bolts failing. The results of this failure have been life threatening to say the least. Any advise on how to prevent this situation ? Is there a fastener to avoid and would coating the fasteners be effective in retarding corrosion? I suspect that these fasteners may be made from steel. If that's the case could you recommend an alloy from which I can make my own? The failures I know of have been on boats used in salt water.
Thanks, Jon"

"The originals are made out of

"The originals are made out of galvanized steel, and they do last for a long, long time even in salt water. I have seen bolts 30 years old and, even if the galvanized layer was gone in some of them, they showed no signs of wastage.

IMO, if you replace yours with the original VP bolts (I know, I know, they are expensive) they will likely last longer than your boat."

"Hi El,
If thats the case, th

"Hi El,
If thats the case, then what is causing these bolts to fail? Is it possible that the boat manufacturers are using inferior bolts to cut costs? Would a manufacturer need to go to a longer bolt due to transom thickness? Just curious and a bit nervous.

Thanks El, Jon Allen"

"Jon, how old were the bolts y

"Jon, how old were the bolts you are talking about? Galvanized steel is corrosion resistant, but it does not last forever.

When the bolts (part 58) are installed, they are sealed between the transom shield and the transom by means of the soft rubber o-ring (part 59), then the washer (60) and the nut (61) go on the inside of the boat. That should give sufficient protection to the bolt shank if there were no water leaks into the transom, but that cannot be always guaranteed. To be on the safe side, I coat the bolts with Sikaflex at the time of installation to give them extra protection against corrosion.

http://www.volvopentastore.com/mall/image/vendor/699/EPC/bigger/5262_big.png"

"John, you may have another is

"John, you may have another issue taking place re; your corrosion!
In all of the years that I have been doing the AQ series Volvo Penta drives, I've seen only a hand full of severely corroded/rusted bolts. And the transom shields that these were removed from showed severe signs of neglect and corrosion as well. Also, the bolt shanks appeared to be incorrectly sealed. (read on re; the chamfered holes)

I'd recommend that you replace them if concerned..... and use the galvanized steel carriage bolts that you can get from a fastener supply company......... (I don't believe that these must be Volvo Penta bolts).
But as El P suggests, the sealing of the bolt shank actually takes place with the rubber sealing rings....... (a fat O-ring to be precise).
This O-ring compresses into the chamfered area of the holes creating the shank seal!
NOTE: I have on rare occasion seen a few transoms whereby the boat manufacturer did NOT chamfer the six holes. This offers NO area to create the compression of the O-ring against the bolt shank! If your six holes are not chamfered, then you must do this!

Add sealant liberally around these six O-rings while assembling the transom shield to the transom.

The larger rubber sealing ring can have a bead of sealant in the groove and at the transom mating surface if you want to do so. (this is what I do).

If done properly, there is no need for any sealant at the perimeter of the transom shield. This is usually a last ditch effort by the un-knowing DIY'er and is often in lieu of a proper repair.

Good luck.

PS, if you follow this procedure, and if these new bolts do not last for 25/30 more years, I'll personally send you six new ones!
."