Outboard motor transom clamps..... necessary?

Recently purchased new 20hp Merc, longshaft. I have a 20” transom but when outboard is mounted the anti ventilation plate is 2 1/2” below bottom of transom. Would like to raise the motor about 3” to get the plate a little above the transom bottom.
My problem is if I raise the motor to where I want it the transom clamps will be mostly above the top lip of the transom.
Short of making a stationery permanent riser out of aluminum(time and $) could I just position the motor where I want it and use bolts through the motor’s transom bracket? I would use an appropriate size shim of the correct height, even though it would not help with the integrity/strength of the connection between the motor and transom.
My transom board is pretty beefy(white oak 59”x1 5/8”x9”, homemade) and the bolts would not be too close to top and bottom of transom edges. Actually, the top bolts would be in the same position as the motor clamps were before raising the motor.
Not looking for a speed increase but the the added lift of three inches would be beneficial in shallow water running.
I’ve never bolted my other small outboards to transom before, only used the motor clamps. I am thinking bolting, even if it’s raised, would be more sturdy than just using the clamps anyway.
Any thoughts on doing this? Can it be done?
Thanks.

If you notice most of the motors have a thick boss up where the clamps are as opposed to a much thinner area down where the bolts go through. I have seen the brackets busted out where the bolts go through, I would say in a perfect world if you never hit anything under full throttle you would be fine. But if you did you would be asking for trouble or worst case snorkeling for a motor.

I had a boat with an oddball transom once and I wound up raising the motor 2 inches. What I did was get 2 pieces of 1/4” aluminum plate and a piece of wood the same thickness as the transom. Sandwiched it all together bolted through the motor and at the top allowing the clamp to be used as well. Just kind of ties everything together.


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nccatfisher— thanks for bringing that to my attention. I’ll take a look at that tomorrow, but I think that you are correct about that part of the motor bracket being designed to handle the bulk of impact shock. I’ve never hit anything before and I do run in some relatively shallow water so I never gave it a second thought.
Thanks for you reply.

Weldor— thinking now that I will go the permanent riser route. I was a welder by trade (retired) and have the equipment to fab up aluminum. Just trying to save time and money by going the bolts only route. Better to do it right the first time I guess.
Thanks.

I think you will be happy having the additional support of the top clamps attached. You may go for years or forever and never have a problem but I have messed with numerous boats over the years and have seen all kind of strange things happen and the end result or even repair some damage that would have been much easier to have fixed on the initial setup.

Like you I have all kind of equipment here to weld and fabricate aluminum and if you have that capability you are ahead of the game. It may take you a few hours initially but once done it is permanent and strong.

Just get one of these.

https://www.iboats.com/shop/t-h-marine-supply-mini-jacker-jack-plate.html?cm_mmc=&gclid=EAIaIQobChMIwYPup-2O2gIVhrbACh1-_gLtEAYYAyABEgKJbvD_BwE

That’s not a bad idea mxmike.


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I ran a T&H mini jacker on my 1436 jon. The set back will let you raise the motor even higher.