What mooring line?
 

Just curious what size mooring line people are using on 30-35 ft boats? 3/8", 1/2" or what else?

for that TUG, I wouldnt use anything less than 3/4" line ..... Just kidding. you should be fine with 1/2" but 5/8' would be better.

We have 4 25ft, 3/8in 3 15ft 3/8in, 4 30ft 1/2in and 3 25 ft 1/2in, we don't use the 1/2 in very often. The 3/8 lines are good to 4700lb (Breaking Strenght) and the 1/2 are @ 8500lb We have a 382 formula and the boat is 10500 lb dry !!!

Personally, I like the smaller ropes. It isn't like I keep the boat in the water so the most I'd ever have to deal with would be a thunderstorm that snuck up on us.

The smaller ones just seem to be more friendly.

TUG??? ROFLMAO I figure double-braided 1/2" would be more than enough for this once it does hit the water. I don't think the cleats are big enough for anything bigger anyway. Like some others I doubt it will be left in the water very often other than a night here and there. I was just curious about what others prefer.

Only one way to go IMO...

http://www.mooringlines.com/lines.htm

I use the 5/8" on my 26' boat and I do not believe they are overkill. As for length, it like the shorter lines for tying off the stern and the longer lines for the front so I can do a spring line.

I prefer 1/2" for all around use and docking but if you tie up with smaller boats (especially Crownlines) 3/8 will work.
Run 25' at the rear and 25-30' at the bow.
When rafting with boats, the extra length makes line splitting or boats pulling out safer and easier.
Docking or comming along side, length makes the difference between a catch and a second throw (which may be too late and more boat manuvering is needed).

I use 1/2" premade high quality dock lines for tieing up to other boats and docking. I used to have 5/8" anchor line and it was overkill for a 26' boat, but it didn't get tangled up. Long story, but I ended up loosing my 5/8 anchor line. This time around I bought 1/2" and I HATE it!! It seems to get itself tangled and knotted all the time...... I am going back to 5/8" anchor line very soon.

I would go with a large of rope as your cleats will accomidate. Bigger line will never hurt maters...... If for some reason you need a tow or had to tow some one, you will thank yourself for the buying the larger diameter line.... I yanked a smaller beached boat off of an island after a storm with my 5/8" line. I wouldn't have done that with 1/2".....

I have a Formula 34 PC, use 5/8 lines for everything. One of my friends refers to them as "Queen Mary lines" :P

The problem comes in if you hang out with any smaller boats, sure my massive cleats can handle it...but your average Mastercraft etc not so much.

I have been on the fence about getting bigger ones, I like them more when hanging with big boats...I suppose I should just tell a smaller boat to use their own damn lines if their cleats are too small :)