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Old 09-11-2018, 10:50   #1
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Join Date: Jul 2016
Location: Cape Coral FL
Boat: Hunter 33
Posts: 156
3ym30 Motor Mounts

I'm going to try replacing motor mounts and some of them the bolt heads are completely rusted off.

Ok so I can get the mounts off no problem, getting the rest of the lag bolt out of the stringer is what I'm worried about

Also, I would rather not replace them with the same bolts that are in there now so what is a recommended bolt for this application?

I have not started the project yet because I'm still trying to figure out how to proceed so any advice would be appreciated
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Old 09-11-2018, 21:20   #2
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Re: 3ym30 Motor Mounts

No simple answer to this one.

To dig the remains of rusted bolts out is likely to be somewhat idiosyncratic to each hole; the one thing that you'll need around all of them is clearance.

If you're not removing the engine, it may be possible to remove each bracket from the engine sequentially and do what you have to do to get the old bolts out. A wood chisel or die grinder may work to expose a section of the bolt to which you can attach a pair of vise grips.

Once you get them out, if the wood isn't rotten or wet, you may be able to just use a longer or oversize (or both) bolt; if this is the case, this is one application where 5200 makes sense,

If the hole is too wallowed out, you'll have to fill it with something; epoxy and milled fibers is a good choice, since it won't rot, but a lot of people hole saw the hole to a standard size and epoxy in an appropriately-sized wooden dowel.

If you can't get the old bolts out, sometimes you can just rotate the mount a few degrees to screw into new material; this is strictly limited by application, some mounts are designed specifically to be mounted fore and aft.

Probably the gold standard for lag bolts in this application would be silicon bronze, but at 7.00 or so apiece for 3/8 x 2 1/2, 316 SS might be almost as good. Plenty of people just use hot-dip galvanized and keep an eye on them.

The problem with both 316 and galvanized is that the heads can appear good, and the business end corroded to worthlessness; good silicon bronze doesn't suffer from this drawback, hence 60.00 or so might make more economic sense in the long run...
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