Okay everyone - Here is what I found! (click images to enlarge)
I got to the boat on Saturday morning and with the help of my lovely assistant (the Admiral) started to check a few things with my new toy from Amazon, the usb endoscope. Your device needs to be USB On-the-go capable, and luckily mine is. I bought this one and at $40, I wish I had bought one way way sooner, very basic and very good video quality. I got the USB style over the wifi or bluetooth style as I had read a few reviews
of connectivity issues over the wifi/bluetooth. The cable is semi rigid so you can bend it and hold that shape to get around corners
and such. I used the OTG View app in the Google Play store, instead of the manufacturer's app, there are more options on it and it ran smoother.
I put that camera in the original inspection hole - this has obviously been modified by someone at some point not by me. I put the scope all up and down this port side plate to check its condition as after my phone call with Captain Jerry the H31 owner who lost his rig due to these plates, I wanted to know its condition. There is surface rust and paint chipping due to that, but no major degradation, galling or pitting of the metal that I could see on top of the plate. In doing this I spotted from inside the glass a hole that a previous owner had cut under the settee and behind the water tank. I would not have been able to see this from the outside.
So... Off comes the settee top and part of the cabinet - jeez thats a pain, so many screws and talk about the boat yoga! But its off and that revealed this.
So I knew immediately this meant something bad - that a previous owner had at least needed to go through trouble to put this here in the past, but for what reasons? I had a sinking suspicion. Anyone following the thread may remember the sheared/cut bolt I talked about? Yep...
Since the plate is fairly heavy and I needed to suspend it to more easily get my camera the view it needed I went to Lowes and got a couple fender washers, a 1/2" x 3" carriage bolt and some pvc and made this plate holder.
I'm glad I did it was very helpful in saving the Admirals arm strength and allowed me both hands to operate the camera and snake it from the inspection hole behind the plate and gussets to where I wanted to really see. And what I saw was... (ignore audio - sorry for shaky cam, its hard to move the camera in small spaces)
Thats right folks, the sheared/cut bolt on top wasn't from installing the plate at the factory like some had guessed. It is an original piece of a siezed chain plate anchor. Oh and I found my welded castle nut - it hadn't fallen off from rust at least??
This means previous owners had cut an original chain plate at some point for some unknown reasons to me ( I don't have the history of my vessel) and moved the plate over a scoche and drilled a new hole and secured it with... ? maybe nothing? Maybe something, possible dropping to the abyss between hull and liner?
So I tried with the holder in place to use my dremel tool to square the threads off on the siezed bolt from the top side and allowed PB Blaster some time to do its magic. Used a huge cheater bar for leverage and an adjustable wrench. Notta. Used a huge pair of vice grips and the cheater bar, notta. This thing is not coming out without being drilled out and then re-tapping the nut. Not something that would be easy in this small space. So I decided to not do that.
A more patient person would go with Sailor832's suggestions of using the 3/4" Blind Rivet Nut. But I'm not patient. Another trip to Lowe's.
They have these coupling nuts. 3/4"-10 and are 2 1/4" long. About the same as the original I believe. I got this, a huge 2" wide fender washer, and a 3/4"-10 nylock. I am paranoid about this nut backing off and me never knowing since I can't secure this new nut to the angle, I feel confident with the nylock. The fender washer is because the "new" hole the previous owners drilled is just slightly oversized, really barely and the washer probably isn't needed, but why not? Now how do I install it??
Thankfully Captain Jerry again had provided me valuable information. I knew from some of his other posts that the angle iron is 4" x 4" x 30". The Glass is about 5/8" Thick in the liner. So from the top of the liner I measured about 4 5/8" down and about 1" or a bit more from the big stringer built into the liner and placed a 5" hole with my hole saw. Do not go ANY LOWER THAN THIS OR YOU WILL HIT THE HULL. Stay at least half an inch and ideally more above the bottom curve of the liner. This will get covered with an access plate later.
This allowed me about 1.5" to get my reasonably sized hand smashed in the hole and under the plate. Let me tell you guys, I'm good with my hands and fairly nimble with them and I still dropped one washer into the abyss. Not ideal but not the end of the world. I used a few rags to try to block the hole to the abyss behind the big stringer after this, I don't think it did much and I tried my best not to lose anything else.
With my wife's help her using a huge adjustable wrench and me using a 8" adjustable wrench at an angle we were able to slowly put the nuts on in order tightening until the angle iron was snug up against the liner and would suspend itself so I could then remove the holder. In the future I might consider using a crow's foot or a stubby 1 1/8" wrench to hold the nut while someone from the top turns. But not for another like 8 years at least! Make sure you check the condition of the bolts that go on top of the plate at the deck. Mine were messed up so I had to go get new 1/4"-20 bolts and ran a new tap down the holes just to clean and correct any misthreading issues.
The starboard side chain plate was all perfectly normal and the chainplate was in its original welded nut. So all I can guess on the port side is that someone tried to rebed them at somepoint, found it siezed and went to drastic measures and cut their tie rod and replaced it. I checked my port tie rod furiously for any sign of a "fix" along its length and cannot find any, and its the same length as the starboard one. So I assume it was replaced in its entirety. The same inspection port was cut on starboard and camera used to inspect the plate. Its the same condition as Port side. Surface rust and minor imperfections. I used the holder made and 30 turns later on the starboard side I had it undone and 30 turns to go back on.
I'm happy I don't feel the need to replace the angle as I didn't want to do yet another fiberglass job cutting out the old plate and putting a new one in. This camera and the inspection ports will allow me to get good full inspections of both plates as often as I like top and bottom. Probably every year or two.
Hopefully this thread helps other owners in the future as you all have helped me. I'll be glad to help answer any questions if anyone has any.