Refinishing Outdoor Wood Table

Question

About 3 years ago I built an outdoor patio table from home depot pressure treated lumber. I walnut stained it and applied 3 layers of Helmsman spar urethane. It looks like the sun/rain has worn down the urethane finish so it's time to re-apply. It even looks like some of the stain is fading. I've never refinished wood like this so I have a few questions, which I think I know the answers for, just looking for anyone with more experience to confirm.

1. Is it right to stick with the same spar urethane or should I consider an alternative? (I think the same)
2. Should I expect a fresh coat of urethane to give the stain a more even finish, or do I just need to re-stain first? (I think I need to re-stain, I just don't want to)
3. How many coats of urethane should I do? Should I expect another 3 coats to last me another 3 years? If I only do 1 coat, will I need to refinish sooner, maybe in 1 year? (I think 3 coats would offer the longest durability)
4. How should I prep the surface before refinishing? I've read to lightly sand. If I'm not re-staining, does that mean to hand sand just enough to not remove any stain? Is that even possible? After sanding, I expect the surface will be gritty from what sanding breaks loose. Is it important to thoroughly clean all the grit off before applying the finish? (Was thinking to use one of those fine sponge hand sanders while trying to preserve the stain, and use simple green to clean)
5. Is sanding between each coat of urethane really necessary? Does the same apply for cleaning the surface after sanding and before the next coat? (Probably yes)
6. If I do re-stain, do I need to sand the surface down to bare wood? (Probably yes)

Answer 1

"...stick with the same spar urethane...?"

YES

"Should I expect a fresh coat of urethane to give the stain a more even finish"?

KINDA The spar varnish will slightly darken everything, making the wood look like it would look if wet. Take a damp sponge to it to see if you like the look.

"do I just need to re-stain first?"

SEE ABOVE

"How many coats of urethane should I do?"

FOLLOW DIRECTIONS I usually start with a coat that has been thinned a bit, to facilitate penetration, then follow up with 2 coats.

"Should I expect... 3 coats to last... 3 years?"

DEPENDS There are so many variables that affect finish longevity... but I don't think it is unreasonable to expect to get 3 years out of it. I would plan on giving it a "freshen-up" coat every year.

"How should I prep the surface before refinishing?"

Hand or machine sand lightly with fine grit paper. make sure any bubbled up, cracked, peeling, flaking finish is removed and the surface is smooth.

"Is it important to thoroughly clean all the grit off before applying the finish?"

YES Blow or sweep off the table when done with prep, then wipe it down with a damp cloth. Any debris left on the surface will end up in the finish.

"Is sanding between each coat of urethane really necessary? Does the same apply for cleaning the surface after sanding and before the next coat?"

YES Follow directions

"If I... re-stain, do I need to sand the surface down to bare wood?"

PROBABLY NOT Whether or not you need to sand at all prior to staining depends on whether the old finish prevents stain penetration. If the stain penetrates, no sanding required. I would recommend an initial fine sand prior to checking for stain penetration (if you decide it needs to be stained, I kinda like it as it is).