As was said above, Homes (over long periods of time) appreciate in value, boats ALWAYS depreciate in value, the rates are higher as the risk to the bank is higher (we could have a huge discussion on the sub-prime collapse, but thats a different story...).
The best way to buy a boat is CASH, plain and simple. If you ever need to sell it, you get CASH, no being up-side-down in a loan... and so on. If you MUST take a loan, be VERY careful of a home equity loan, as millions of folks have found out in the last 2 years, if you can NOT pay your home loan, you loose your HOME. On a boat loan, the worst that happens if you default is they repo the boat, and down your credit limit. now if you are financialy secure, have a lot of equity in your home, KNOW you can survive on your savings for 12 months or longer if you loose your job and NOT miss a mortgage/home loan payment, then ... As long as the boat loan is a simple interest no-penalty for early payoff, take the longest loan period that gives you the best rate, and pay the boat off in 1 year.
Mat - I disagree on the staying a way from a 15 year boat loan, IF you are financialy sound and have backup/savings. I bought my tracker and really wanted a 2 year loan, as I had just changed jobs, and while I had the cash to buy the boat, wanted a buffer the first year in a new job, just in case. The best rate was on a 15 year simple interest/no penaly early pay off loan through tracker. Took the loan, figured out what the payments SHOULD be on a 2 year loan, paid it like it was a 2 year loan and ended up paying it off in 18 months. I could have gotten a much larger loan for a much larger boat, but didn't want the risk of needing to sell it if the job didn't work out and be in the hole.
So, its your choice - If you take the risk on a long term loan to get your payments to 'affordable', you MUST make the decision to not sell it till its paid off, pay it off early and so on... If you decide to pay it off on the longer term of the loan, then you are agreeing up front you will pay all the interest and wouldn't it be better to wait 2-3 years till you can pay cash, or buy a nice used boat like I did for my second boat for cash.
Trep