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Old 10-16-2021, 06:57 PM   #1
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Grand Banks motor mounts

The stringers by way of the motor mounts on my 1979 Grand Banks 42 apparently are hollow hat sections with maybe 3/4" wood at the top capped by an aluminum extrusion. One of the motor mount bolts came loose. On inspection, it appears to have been threaded only to the aluminum (?) and wood. No metal fastener below as far as I can tell. This seems lightweight for a heavy 120-hp Ford Lehman diesel engine. Does anyone have experience re-securing loose bolts?
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Old 10-22-2021, 11:31 PM   #2
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Any way you can take a picture of the set up?
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Old 10-22-2021, 11:45 PM   #3
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Welcome aboard. Yes photos would help.
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Old 10-23-2021, 10:05 AM   #4
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Not to hijack thread, but I would like to replace my mounts with exact dimensions if possible.

Any input appreciated.
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Old 10-23-2021, 11:25 AM   #5
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Cut or drill an access hole in the side of the stringer and insert a backing plate and nut to bolt the engine mount to.

I weld the nut to the backing plate so it will not spin and ease installation. I cut a slot big enough to slide the backing plate in and install the bolt. Pliers can be used to hold the plate while inserting the bolt. Once the bolt is threaded, the plate will prevent bolt spinning.

Or glue a paint stir stick to the backing plate and hold that while inserting the bolt and cut or break the stick off when done. This method prevents dropping the plate inside the stringer.

Patch the access hole with FG and epoxy.
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Old 10-23-2021, 11:37 AM   #6
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Quote:
Originally Posted by Choices View Post
Not to hijack thread, but I would like to replace my mounts with exact dimensions if possible.

Any input appreciated.

PYI carriers a wide selection of engine mounts:

https://www.pyiinc.com/engine-mounts.html

The website has instructions on calculating the load weight on each mount in order to choose the correct mount. Or you can contact them and they will assist with the calculation.
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Old 10-24-2021, 07:42 AM   #7
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Quote:
Originally Posted by syjos View Post
Cut or drill an access hole in the side of the stringer and insert a backing plate and nut to bolt the engine mount to.

I weld the nut to the backing plate so it will not spin and ease installation. I cut a slot big enough to slide the backing plate in and install the bolt. Pliers can be used to hold the plate while inserting the bolt. Once the bolt is threaded, the plate will prevent bolt spinning.

Or glue a paint stir stick to the backing plate and hold that while inserting the bolt and cut or break the stick off when done. This method prevents dropping the plate inside the stringer.

Patch the access hole with FG and epoxy.
Thanks. I've come to the same conclusion that drilling an access hole in the side is the best route. The stir stick is a good tip. I still wonder how the bolt was originally secured.
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Old 10-25-2021, 07:21 AM   #8
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Here is a photo. Below the aluminum cap is 1/4" of filler and below that maybe 3/4" wood. The rest of the stringer is filled with foam. Another thought is to drill a hole from the top (rather than the side) between the two bolt holes and slip a plate with welded nuts inside. I have a photo but don't know how to assign it a URL for posting.
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Old 10-25-2021, 10:09 AM   #9
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Quote:
Originally Posted by DSPURR View Post
Here is a photo. Below the aluminum cap is 1/4" of filler and below that maybe 3/4" wood. The rest of the stringer is filled with foam. Another thought is to drill a hole from the top (rather than the side) between the two bolt holes and slip a plate with welded nuts inside. I have a photo but don't know how to assign it a URL for posting.
To post pictures, click on Go Advanced at the bottom of Quick Reply.

On the Advanced Reply to Thread at the top header, click on the symbol that looks like a paperclip. Next to the smiley face.

That will take you to the Manage Attachment page. Click on Choose File and attach your picture. When done click Upload.

Return to the Trawler Forum tab and post.
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Old 10-25-2021, 01:13 PM   #10
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Motor mount photo

Grand Banks 42 motor mount.
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GB Motor Mount.jpg  
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Old 10-29-2021, 03:59 PM   #11
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Engine mount isolators

BTW, does your mount look like this picture? I just spent hours this month trying to find a substitute for the rubber isolators. After drilling out the crimped sleeve, I replaced the bottom mount with a polyurethane ATRO part PL1017. AT first I tried a rubber part but the shore hardness (50) was too soft. You need to shave down the diameter slightly. The top mount is the same, but you need to cut off the bottom.
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Old 11-01-2021, 06:14 AM   #12
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Originally Posted by GB42-424 View Post
BTW, does your mount look like this picture? I just spent hours this month trying to find a substitute for the rubber isolators. After drilling out the crimped sleeve, I replaced the bottom mount with a polyurethane ATRO part PL1017. AT first I tried a rubber part but the shore hardness (50) was too soft. You need to shave down the diameter slightly. The top mount is the same, but you need to cut off the bottom.
Similar, but not exact. There are rubber isolators. Replacement sounds like a difficult job.
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