The quote from the local boat place on Oahu was around $1000-1100 for a galvanized 12inch tires bunk style trailer. It's a regular boat trailer with a payload of 1200-2000lbs. I really need only a 600-900lb payload type trailler.
Being garage space limited the foldable trailers seems like a good choice but none of them are galvanized.
Since they are sold as trailer kits that require you to bolt it all together, the shipping in multiple boxes is a plus rather than a totally assembled one that you would have to find a freight carrier to deal with. Your needs may be the opposite.
The Price is the issue here:
These trailer kits costs $375USD - $1400USD. The ones I'm closely looking at are in the $400-600 USD cost range.
There are powder painted steel, galvanized, and aluminum choices on the finish.
I thought I had to purchase a galvanized trailer kit, but some of the makers offer that option for an extra charge of $112 which sounds like it's worth it to add to your options.
I didn't see any aluminum trailers for less than $1100-1500USD; some payloads were less than 500lbs.
Some of these trailer kits are not really designed for boats but more so for a 4ft X 8ft flat bed. With these types you may need to add the winch post, winch, bunks or bunk cloth material so your boat can slide onto the flat bed. I would not use this type of trailer without putting the plywood down on the flat bed, or I'd install two 5ft bunks at the back half of the trailer if you don't like the flat bed option.
For the amount of freeway driving the trailer needs to do, I'm opting for the 5.80 X 12inch tires.
My motor weight of 105lbs, + boat 200-250lbs and maybe 200lbs of dive gear is under my requirement for the payload restriction of 600lbs.
So my choice would be to get a Red Trailer or Amorex foldable flatbed trailer that I could galvanize the steel parts and put together as a kit for under the $800USD price tag. The CE Smith trailer kits area just under $800 USD too but they are not foldable or break down easy to store away.