Bang Cap vs. Bracket

[Ridge Runner]

I replaced my Bang Cap with 1/16" Stainless while I had the motors off. The brackets did mash down against the old aluminum Bang Cap,and there was some corrosion but not really bad. I dry fitted the brackets before caulking, and the gap is noticable. I haven't cranked the bolts hard yet, just with a light impact. Question is, would you just torque them down and make sure the gap is sealed with caulk, or cut the Bang Plate so the bracket is flat against the transom?

 

[Fishtales]

I think I'd leave it as is and torque down. Will be interested in what others think....

 

[blindmullet]

If you can make it flush I think you're better off, but probably wouldn't make a difference. Any corrosion on the back side or is there a thin plastic gasket (my Grady had one)? There could be a possible dissimilar metal issue with the stainless and aluminum, but probably overthinking it.

 

[Fishtales]

Interesting. I was thinking about being flush not dissimilar metal issue. I still think I'd just lock it down and go with it versus trimming it back to eliminate contact.

 

[DennisG01]

I may be overthinking this, as well, but...

-- I'd also be concerned about galvanic corrosion, so having some type of non-metal spacer between the bracket and the cap would be good.
-- And, I think I would feel better with flush contact of the bracket to the hull rather than one, sharp point at the bottom that "could" (in theory, anyways) dig into the transom or at least spider-crack the gel. Another piece (or two strips, anyways) of that stainless being used as spacers would do the trick (with a non-metallic piece separating the two metals).

Whether these things are needed... I suppose that could maybe be up for debate. But in my opinion, it certainly can't hurt to do these things - it can only make it better.

 

[wrxhoon]

I'm with Dennis, isolate it with none metal and use a spacer same thickness as the S/S you used.

 

[Halfhitch]

This how Trapper took care of just what you are talking about. He always does stuff first cabin.
Oops, can't do that on my Ipad. Just a minute here.....

https://www.greatgrady.com/threads/transom-cap-bang-plate.25669/

 

[Fishtales]

Either way, the last one got you 16 years and you indicated it wasn't bad. Whatever you do should get you close to 20 more. By then the hull is 34 years old!

 

[Doc Stressor]

I would worry a lot about galvanic corrosion of your aluminum engine bracket. There is no way that this is not going to eventually occur if you clamp it onto a piece of stainless steel.

You might consider a manual jack plate that will mount on the transom below the bang plate. I used the one in the link below when I replaced my bang plate with the never vinyl product. While galvanic corrosion would not have been an issue, mounting the engine would have distorted the bang plate, which is what happened on my original aluminum bang plate. It's hard to keep it well sealed in the area behind the engine mounting bracket.

The jack plate offers some performance and fuel economy benefits as well as solving your galvanic corrosion concerns. It's pretty cheap and are easy to install.

Bob's Machine Shop Manual Jack Plate

 

[Doc Stressor]

Here's a picture showing how the Bob's Machine Shop jack plate solves the bang plate impact problem. The mount is notched so that the top doesn't come in contact with the bang plate. At least the aluminum or vinyl bang plate. Your SS bang plate may be thicker.

 

[Fishtales]

It looks like there is an area of connection about 7/8ths of the way down the notch. It doesn't look like you have experienced any issues though.

 

[Doc Stressor]

It gets close, but doesn't actually touch the bang plate. A little silicon sealer would prevent any conductive contact if it did.

You could also use a Dremel to cut a shallow groove in the jack plate if it did come in contact with the bang plate.

 

[Ridge Runner]

This how Trapper took care of just what you are talking about. He always does stuff first cabin.
Oops, can't do that on my Ipad. Just a minute here.....

https://www.greatgrady.com/threads/transom-cap-bang-plate.25669/

I'm going with Trapper's logic. Ordered some 3/16" and will make shims. That should hold the brackets off the 1/16" bang plate just enough for a caulk barrior. Will update again when done!

 

[HMBJack]

I am curious about two things:

#1 - What is the purpose of the bang plate? (besides causing corrosion!)

and

#2 - What exactly is under the bang plate?
Like - at the factory - is it Grady's practice to fiberglass and therefore seal the very top portion of the transom?
God help us all if the top of the transom is NOT sealed!
I'd be inclined to not have a bang plate so I could see and monitor the condition of my transom...