Broken forward motor mount studs - 454 w/ B3 - 1996 Splendor 240

[Redhook98]

I just bought at 1996 Splendor 240 with a 7.4 LX and B3. Boat is in fantastic shape and only has 280 hours on it. I was scrambling around the engine compartment and noticed that one stud on each forward motor mount was sheared off. The mounts were not lag bolted in but rather had SS studs coming up from the hull. The Splendor is a cat hull, so stringers in that area are not real large. One stud is holding the mount just fine on each side, and apparently has been for some time. Quite sure the previous owner had no idea.

Pulling the motor in this boat is not an option at this time. Putting a lag bolt in may not be an option due to the pad that the mount is secured to being very thin (hence the reason the studs are there?) How long of a lag bolt would suffice anyway?

What options do I have here? If I try and lag bolt anything in, I risk compromising the hull. Can I survive with one bolt per side? If I had never noticed, would I ever have? baby it and move on with my day?

Thanks!

 

[Bt Doctur]

Are you abel to bolt alum angle 3 x 4 x 1/2 or 3/4 to the stringers and bolt the motor mouts to them?

 

[Redhook98]

No Title

That was my first thought as well. The hull slopes down in that area and a "pad" was built into it to support the studs and mount. The pad is between 1 inch and 1/2 thick. There is no defined area to bolt anything to for a repair plate/panel. Here is a pic when I first noticed it. I was cleaning the engine compartment and was blindly taking pics with my cell phone over the side of the motor. The slope you see around the pad is the hull.

 

[Redhook98]

Looking at the pic, maybe a 2-inch SS lag bolt going in at an angle just off from the stud may work. I can turn the mount a little and take advantage of the elongated hole. ??

 

[fhhuber]

Looks like PITA to fix...

I bet there's a metal stud plate fiberglassed in there.
There is a CHANCE the studs are threaded into it.
hopefully this is the fix, because that's the easy fix.
Pull the mount out, unscrew the bad stud remains and screw a new stud in, then reinstall the engine mount.

yep... gotta jack up the engine a bit to get the mount out for any fix, then you have to recheck the alignment to the drive line.

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The mount adjustment looks like a bit more than 1/4 inch down available? (as in it could adjust OK with 1/4 inch plate under the mount)

Thinking about an idea of how to potentially add a new U channel as a mounting plate...and bolt it to new pieces fiberglassed in at a short distance from the current mount.
U channel because of how I am envisioning bolting it in.
It would be odd... but stiff and strong. And if the studs in that sheared, it could be pulled out to replace the studs.
Avoiding grinding out more than to have a flat surface. (the old studs)

More pictures showing what room there is to work with.... Lay a ruler in straight fore and aft with the 6 in mark at the motor mount

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The second stud or mount will eventually fail. Eventually could be tomorrow... or 20 years. It might fracture the "flange" off the side of the mount instead of shearing the stud.

 

[Rick Stephens]

That picture makes it look like the existing stud end of the motor mount is sitting on metal and the end with no stud is sitting on glass?

 

[Redhook98]

Yeah, I think that was a shim for the mount and it vibrated out of place when the stud broke. Stud is broke below the level of the fiberglass bedding covering the stud mounts.

 

[Bt Doctur]

You can drill a small test holes1/16 to see if there is a plate where it is and how thick it is. shift the motor mount and drill and retap a new bolt hole

 

[Rick Stephens]

Wonder why the shim? Mounts have plenty of adjustment without. That shim does leave open the possibility of making a larger shim with a stud built into the shim over the broken stud, and then offsetting a lag bolt elsewhere. I don't see a way to make this repair proper without pulling the motor. Anything cobbled with motor in place doesn't look as easy as pulling the motor would be, or sufficient. And motor mounts with one mount bolt are asking to rip loose at the wrong place and time.

 

[Scott Danforth]

I would pull the motor. Since the drive will need to be pulled anyway to align the motor. Pulling the drive is half the battle

 

[Bondo]

Ayuh,...... That appears to be some 1/2azzed engineered mount, that's only 1/2 there,.....

I'm with Scott,...
I'd yank the motor, 'n re-engineer a better mountin' system altogether,....
If nothin' else, butt weld the missin' piece in place,...