Super rusted nuts on my Hobie 18 rudder

Actually after taking a close look while taking the pictures, it might not be as big of a problem as I had originally thought.  Since it looks like the bolts were stainless, unlike the nuts that obviously were not, that maybe just vice grips and a socket wrench and some hawk-tuah might get it undone  I just don't want to hurt the expensive rudder at all, and hope it will just spin off for me.  Rebuilding the rudders is my last task to be able to sail her for the first time.

Use pb blaster 2 times a day for 2 days. Then use some locktite freeze and release spray right before you remove them. should come right off. Stainless has a bad habit when mixed with Non to ball up metal and lock up half way off. Good luck!

At least those are pretty accessible.  You could cut those of pretty easily, if you can get them to turn.

Use pb blaster 2 times a day for 2 days. Then use some locktite freeze and release spray right before you remove them. should come right off. Stainless has a bad habit when mixed with Non to ball up metal and lock up half way off. Good luck!

If the rudder is plastic, you'll want to avoid getting spray on it...

Use pb blaster 2 times a day for 2 days. Then use some locktite freeze and release spray right before you remove them. should come right off. Stainless has a bad habit when mixed with Non to ball up metal and lock up half way off. Good luck!

If the rudder is plastic, you'll want to avoid getting spray on it...

PB blaster is peanut oil. Doesn't hurt plastic in my experiance. the other product is propane. Dont light a match!

+1 on penetrating oil a few times a day for a week or so (I use Kroil, but you'll find no shortage of opinions on which penetrating lube to use).  I also tap with a hammer a bunch of times each time I add penetrating lube to help crack the bonds and let the lube get farther in.  For those nuts, I'd use a nut extractor on an impact once you're ready.  Bring a cutoff wheel, too, because it's likely you'll just need to shave them off in the end.

I can loan ya the nut extractors and some Kroil if you don't feel like purchasing.

Btw, I had some rusty bolts on my Trailex trailer. Not fun!

https://www.norcalkayakanglers.com/index.php?topic=99976.0

Well, it's not going well...    I just cant seem to be able to get a bite on those nuts to twist them off.  I tried using vice grips and a vice mounted to a table, but I just cant get it to not spin when I try and twist the bolt, the metal just shaves off.  The bracket is slightly in the way too get a full contact on the nut. I'm thinking of trying to hammer on a smaller bit through the rust and see if I can get it to twist off then.

Could try something like this - confirms to the shape of your fastener regardless of size/shape. I've used it for light duty stuff with good success.
Super Universal Socket Tools
 https://a.co/d/cOw8IuE

Could also take a cut off wheel to it ... That's probably the direction I would go with that one.

Also, PB Blaster is your friend if you really want to get it apart without ruining the bolt.

Could try something like this - confirms to the shape of your fastener regardless of size/shape. I've used it for light duty stuff with good success.
Super Universal Socket Tools
 https://a.co/d/cOw8IuE

Could also take a cut off wheel to it ... That's probably the direction I would go with that one.

Agreed. A Dremel with a cut off wheel will have them off in a few seconds.

I have used small pipe wrenches for bolts that have become striped.

Wouldn't hurt to check out Harbor Freight and get some knock-off Knipex pliers.  They work wonders.  If you think you'll have more use for them after, go all in on the Knipex.  Their pliers wrench and cobra pliers are top tier; the metal they use really bites into the bolt and I've personally never experienced slippage, though I don't think I've experienced something that rusted. The penetrating oil will also definitely help. 

I cant get it un-done with brute force, the nut's metal just gives way.  Seems like I need to cut or drill it, but not sure how that can be done really.  They are recessed a little bit in the rudder housing, so I dont think I can get a flat cut in with a hack saw. They do still turn though, so maybe drilling the center out would work?  Probably take forever though without a drill press.

I cant get it un-done with brute force, the nut's metal just gives way.  Seems like I need to cut or drill it, but not sure how that can be done really.  They are recessed a little bit in the rudder housing, so I dont think I can get a flat cut in with a hack saw. They do still turn though, so maybe drilling the center out would work?  Probably take forever though without a drill press.

What do you have for cutting tools?  I would try a vertical cut, getting as close as you can without hitting the surrounding surface.  Would take a while with a hacksaw, but you should be able to remove enough material to just break what remains of the nut in half.  Those stainless bolts probably won't be fun to cut by hand either.