A boat loan is ordinary amortization. The payment formula is not mysterious, and it is not the ownership bill.
monthly = principal × r × (1+r)^n / ((1+r)^n − 1)
where r is APR divided by 1200 and n is months. If the rate is zero, the payment is principal divided by months. BoatCost implements that in lib/loan.ts and tests it. The default scenario is 8.3% APR, 10 years, 20% down. That is an illustration rate, not a quote. Enter the APR on a written offer.
This guide is about the gap between that payment and the number that leaves your account. Open the ownership calculator with your price and term, then keep reading.
The payment is one row
On a $55,000 bowrider with $11,000 down, principal is $44,000. At the illustration defaults, principal and interest are the line a sales worksheet often highlights. Insurance, trailer or slip, registration, estimated fuel, and maintenance sit next to it. In a warm state on a trailer, those extra lines often rival the loan. In a high-slip coastal state they can exceed it.
The loan does not care whether you launched. A wet slip does not care either. Fuel and maintenance do. If you only compare boats by payment, you are comparing the one line that is easiest to advertise.
Worked pattern — example calculator inputs, not a quote:
- Price $55,000, down $11,000, APR 8.3%, 10 years
- Florida, trailer storage, 200 hp, 50 hours, 20 outings
- Read all-in monthly and cost per outing, not payment alone
Change APR to the number on your paperwork. Change storage if you have a slip quote. The share link keeps the scenario.
What amortization actually does
Each payment is part interest and part principal. Early years are interest-heavy. That is why a boat can be year-5 underwater in this model: the remaining balance is compared with a depreciated value curve (15% the first year, then 10% per year). That curve is a planning check, not an appraisal.
A longer term lowers the monthly payment and usually raises total interest. It does not lower the slip. If a dealer stretches you to 15 or 20 years to “make it fit,” re-run the calculator at both terms and look at year-5 balance vs value. The comfortable payment can be the riskier loan.
A larger down payment cuts principal, interest, and the chance the loan outruns value. It is also cash you cannot put into a reserve for engines and yards. The calculator will not make that trade-off for you; it will show the payment and equity lines if you change down.
Zero-interest dealer promotions still need the rest of the stack. Set APR to 0 only if that is the written contract. Then add insurance and parking. A 0% payment on a boat you cannot moor is not a bargain.
Paid-for is not free
Choose Paid for — no loan when there is no note. Principal and interest drop to zero. The boat can still cost hundreds a month. That is the point of all-in framing. Buy vs rent treats a paid-off purchase as cash paid up front over the comparison horizon, minus estimated value at year N.
If you are moving from a loan to cash, run both and look at cost per outing. People who “already paid for the boat” still pay to keep it wet.
Illustration rate vs shopping rate
Boat lenders price risk, collateral, and term. This site is not a lender. The default 8.3% exists so two boats can be compared on the same page. It is labeled on the form.
When you have a real offer:
- Enter that APR and term.
- Enter the fees that were rolled into principal if they are in the note.
- Leave insurance and slip as quotes if you have them (overrides win, including 0).
- Copy the share link before you compare a second boat so you do not mix APRs.
Do not average three internet rate articles and call it your number. Do not use this page as a credit application.
How to compare two financed boats
Same down-payment percent, same APR, same term, same hours, same storage mode — then change price, length, and horsepower. If one boat needs a wet slip and the other trailers, that is a real difference; do not hide it by leaving both on trailer.
Then open buy vs rent with the same query string so the club and rental piles use the same boat. A loan that “fits” can still lose to a club if you boat eight days a year.
Related reading on this site:
- True cost of boat ownership
- Wet slip vs trailer
- Boat club vs buying
- First boat budget under 30 feet
- Total cost by boat size
- Cost estimates by type and bowrider hubs, or bowrider in Florida (defaults you overwrite)
What the loan does not include
- Sales or use tax collected at purchase (see the state block on a cost page)
- Documentation or dealer fees unless you add them to price
- Hurricane haul-out, named-storm deductibles, or survey costs
- A truck and hitch
- The first engine replacement
If a line is large and known, put it in price or in an override. If it is unknown, do not invent it in the calculator and then treat the total as a quote.
Pros and cons of payment-led shopping
Pros of looking at the loan first
- You see whether a lender will even finance the term
- Amortization is well-defined and testable
- Share links make APR and term visible to a second person
Cons
- Hides slip, insurance, and fuel
- Encourages stretching term to hide a too-large boat
- Makes paid-off boats look “free”
- Invites comparing a trailered pontoon payment to a slipped cruiser payment
Who this is for
- Shoppers holding a dealer worksheet
- Owners refinancing or paying off early who want the rest of the stack
- Anyone comparing own vs club with the same boat assumptions
Alternatives
- Payment-only loan calculators (P&I only)
- Lender disclosures (authoritative for the note; silent on slips)
- Ownership calculator for the combined bill
- Boat insurance cost factors for the premium line
FAQ
Is a longer term always easier? It is easier on the monthly payment and usually harder on interest and underwater risk.
Should I include tax in the loan amount? If the lender is financing tax and fees, add them to price so principal matches the note. The state sales-tax paragraph on a cost page is general and is not a tax calculator.
Why does Florida trailer storage still add a lot besides the loan? Insurance, registration, fuel, and maintenance still bill. The loan is one row.
Can I model extra principal payments? Not as a separate control. You can raise down payment or shorten term as a proxy, then replace the result with your lender’s payoff schedule.