Transom backing plates-much needed or mostly cosmetic?

[Highcentered]

Transom Backing Plates - Bob's Machine (bobsmachine.com)
My Xpress had the motor bolted straight to the transom when I bought it and we installed a 6" Bob's. Almost bought a backing plate for the top pair of bolts but decided not to. Any reason an aluminum boat with a 115 would need a backing plate on the inside of the splash well or would it just be wasted money and effort? My boat is a utilitarian tank I fish out of and not really concerned about extra bits of lipstick for it if not needed. If it didn't have one there to begin with it makes me think it's just cosmetic on these boats but there is more leverage there with a jack plate.

[retiredmechanic]

I look at it like this, you moved the engine back 6 inches so more leverage on transom. I myself would put backing plates on.

[Redngoo]

I feel like that plate should be standard on all boats with a transom and a outboard. Can you imagine the forces created by the engine? It would probably surprise a person.

[Grizzly]

Won't hurt anything.

[trashmanssd]

Spreads the weight and clamping force out. Do you need it maybe not but if I am pulling the transom bolts out and re sealing the holes I would add them.

[fishin couillon]

My Phoenix came with the upper from factory, not sure about lower........would need to take a look. If i didn't have one, i'd add it.

[BRNut]

What would it hurt to spread the load to more surface area?

High thrust loading in reverse can also pull on the bottom, but nothing like the pull on the top.

[Bass Cat Boats]

We use 3 backing plates at all three bolt locations for our six bolt plates. We suggest backing plates on most anything that has stress involved.

[Highcentered]

I have the Bob's upper backing plate on the way. Probably don't need it but it will make me feel better and it looks good. About puked when I saw the shipping cost...

[Grizzly]

I have the Bob's upper backing plate on the way. Probably don't need it but it will make me feel better and it looks good. About puked when I saw the shipping cost...

Gotta pay those UPS drivers.

[Highcentered]

Gotta pay those UPS drivers.

It was FedEx but probably same difference...

[billnorman1]

They don't cost nearly as much as a rebuilt transom. I don't have colossal horsepower (200) but hell, I put two on my old beater boat.

[Thamelau]

I would go with the rather safe than sorry boat myself. It absolutely won't hurt the situation. If the price hurts then you could fabricate your own out of some similar thickness aluminum or stainless fairly easily.

[Highcentered]

Backing plate came in yesterday and I installed it today. I jacked the plate up all the way to have more room to get the wrench on the nuts and kept the transom saver on hoping it would apply upward force to take most if not all stress off the top bolts. Pulled each bolt one at a time and the bolts slid right out. Only a fool would pull both bolts doing this the way I did it! With one bolt through the backing plate with nut on finger tight I pulled the other bolt and ran it in then torqued both. I expected the top of the jack plate to separate a hair from the transom with just one bolt in there still loose enough to push the backing plate down to run the other bolt through it but it didn't so I guess the transom saver kept pressure on the top. I'm just glad we didn't have to loosen the bottom bolts and lift the motor up a hair to take pressure off the top bolts.

[plki]

I have had both upper and lower plates on my little 16ft Nitro. Figured it will help support the 375lb optimax

[plki]

20200426_175538.jpg

[plki]

I installed the brace when the boot was a month old. 20231105_142650.jpg

[billnorman1]

When you remove the bolts you will likely find the washer (there better be one) under the bolt or nut, has sunk into the fiberglass especially on the bottom ones. That's why I would put a backing plate under both.