Whatever you decide, you're looking at a big project. But it's always worth it when it's done!
A couple of things to beware about. Be careful sanding the bulkheads, it's a veneer and you can sand the grain off...which I did.
There is more wood than you realize! MUCH more...
I removed everything including the kitchen sink and took it home with me, spent the whole winter redoing. I sanded all the original red stain off the teak going from 100 grit to 220/440 grit. I then re-oiled all the teak.
For the interior I used an off the shelf gloss/spar finish from MinWax from Home Depot. It is fairly cheap, goes on very easily and finishes nicely. I don't know how this would hold up for exterior wood, but the only issue on interior wood would be latent moisture and closed in heat. After one summer, everything held up nicely.
As far as the finish, I thinned the first coats by 50%. I put the first two coats on within 30 minutes of each other as they soaked into the wood rather quickly. After 24 hours, I 220 grit sanded everything, then 0000 steel wooled it. Wiped it down and put another 2 coats on after thinning by about 30%, there was about an hour wait between these coats.
After 24 hours, I sanded any drips or sags completely.
The next 4-5 coats I progressively thinned less and less until the final coat had barely any thinner added. I aggresively sanded any mistakes before the next coat.
I used 2" foam brushes and they worked just fine.
Loading up...this was trip 1 of about 4! I wasn't kidding!
Before I bought boat...sorry I should have removed the table, but you can see a round stain to the left of light.
Hey! I found one with the table missing! Notice the stains, velcro, etc.
This was after the teak oil and the first 2 coats of thinned varnish. Notice how I got too close to the veneer on the right of the main bulkhead and around the trim on the clothes closet...what a noob!
The finished product. I forgot to tell you, I took all the fiddles apart...I put each individual spool and put them in my drill press. I sanded each one down, oiled them and then put 4 coats of varnish on each of them before putting the fiddles back together.
NOW THAT WAS STUPID! Towards the end, I just threw them in a cup of varnish, shook them around and dumped them on my tool bench. Drips be damned!
Overall I'm happy and since I never spend any time down there, it was well worth it! Woot!