I heard you can write off the interest on your boat as a second mortgage. Does anybody here do this or have any info on what the qualifications are?

Only if it has a head, and you can sleep on it.

Does a sled with sleeper seats, full top with back curtain count if I have a Port-a-potty?

It has to fit the "bed, bread, and head" rule. Basically "permanent" fixtures that would allow sleeping, cooking, and sanitation facilities. Permanent means built into a boat.

Neither example given would fit the rule. Few cuddy boats less than 20' qualify, but generally boats over 25' have no problem qualifying.

........or if you bought the boat with a line of credit secured by a second on your house.

I think you have to sleep a minimum of 2 weeks a year on the boat to qualify along with what was already mentioned.

I'VE ALSO HEARD YOU COULD DEDUCT YOUR GAS FOR YOUR BOAT IF IT QUALIFIES AS ONE WITH THE BREAD, BED, & HEAD RULE. COULD BE JUST THE GAS TAX, BECAUSE THOSE TAXES ARE SUPPOSED TO BE USED FOR ROAD CONTRUCTION OR WHAT EVER & YOUR NOT ON THE ROAD. DOES ANY ONE KNOW IF THAT IS TRUE? COULD BE ALOT OF MONEY IF YOU'RE OUT OFTEN.