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Hey Guys,
I was checking the tightness of my motor mounts this morning.
I noticed on the inside areas of the transom where the large washers meet the transom, the transom is slightly concaved or compressed there.
Is that normal, do I have things too tight, should I be thinking about a larger plate from hole to hole?

Thanks much, still learning here.

Best regards,
Doug

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I wouldn't be depressed. I always used a plate that includes the bolt pattern. My original was a plate just large enough to match the bolt pattern of the motor mounting. Mine was stainless (found a piece at salvage yard). I upgraded to larger aluminum piece that spread the weight even further. The gel coat is pretty thin. A bit of weight directed on a small area. Minimally, I would use over sized washers. The larger the spread, the more relief at the bolts. My motor weighs over 500lbs. However, do check to see if the transom wood is fatigued at the bolt holes.

Garris

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Thanks Garris.

I'll start looking for a plate. I do have over-sized washers currently.
Bolt holes look fine, no fatigue cracks etc.

Best regards,
Doug

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There is a specified amount of torque on mounting bolts.
Check your engine manual.

Boston Whaler never recommended any plates that I have seen in any manuals.

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My recommendation for the plate has no basis on "factory recommendations". It was from observations of boat transoms. Whalers and non Whalers. It is an area of the boat that takes a beating. Especially when transporting on rough roads. I know there are transom saver brackets, etc.... I look at it as an ounce of prevention. I tend to overbuild anyway. Thanks Joe for introducing torque specs. I would have thought the tighter the better. Definitely means the use of lock nuts or double nutting.

Garris

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I looked through my manual and did not find a torque setting for motor mount bolts.
All I found was a standard torque chart that you are suppose to refer to if a special torque setting is not listed.

I guess those may be 7/16 through bolts = 29-30 ft. lbs
3/8 through bolts = 18-20 ft. lbs

I guess it's time I add a torque wrench to my tool box :-)

Doug

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Doug:

There was generally an additional "dealer's" installation manual. I think I've have one in the past. I'll look and see if I still have it.

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Not sure if you are still interested but, I just picked up a 1970 16' Custom and have the same depressions around the motor mount bolts. Since I am going to do some fiberglass repair, I drilled a few holes through the outer hull near the mounts and found the wood to be fine. I did find some wood rot from water near the bottom but it was not related to the mounts much too far down. Just an FYI for anyone else.

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I would not change the retention washers this far down the line. It took 19 years for those depressions to settle in, so altering the pressure points now may cause the gelcoat to crack. When I re powered, I reused the original inside washers to avoid what I thought might create a problem. JMHO of course.

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My engine was originally mounted with stainless fender washers. Although the transom was compressed some around the washers (as one would expect) with an engine weight of ~160# I had no good motivating factor to add a transom support plate.

When I added a jack plate I also added a T-H Marine TSP-1 transom support plate (http://www.thmarine.com/products/Outb...port-Plate). With the plate added it definitely distributes the engine weight very nicely and there is no longer significant compression of the transom. Is it overkill? - probably...but it made for a very nice finishing touch to the engine installation.