Buying a Used Boat: 5 Critical Things to Look For

Since the early days of fiberglass boat construction, techniques for making boats strong and leak-resistant — and cheaper and easier to build — have advanced steadily. The accepted method for most boats today is to mold the hull, deck, and possibly an interior pan, as separate units, often with tabs, stringers, bulkhead reinforcements, and other components included. The hull is equipped with what it needs like fuel tanks, water tanks, plumbing and electrical lines, and so forth. Then the deck is installed permanently on top of it. Well designed and built boats usually offer some sort of access to critical items that get sealed down below. Unfortunately, some boatbuilders, perhaps anxious to get boats out the door and make a sale, can be shortsighted and seal in equipment that’s eventually going to need to be maintained or replaced. But today’s hull-to-deck joints are fiberglassed to make a monocoque construction, or are bonded with extra-tough sealant and stainless fasteners. They are not meant to come apart. Ever. Here are five items that commonly need attention but could prove difficult to access on a used boat, which you should be wary of.

boat hull under construction
With most modern boats, once the deck is attached to the hull the components built in belowdecks may be difficult or impossible to access. Photo via Lenny Rudow.

Fuel Tanks

Tanks that are installed under the deck without access points (preferably inspection ports that offer a view straight to the deepest parts of the tanks) are likely to need attention after a certain number of years. There’s even a chance they may need to be removed and replaced, especially metal tanks that have had saltwater leak on them or held ethanol-laced gasoline at some point. Plastic tanks aren’t as susceptible to corrosion, but their connections can still fail. Sometimes the only way to get at a buried fuel tank (even one with an inspection port in the deck) is to saw open the deck.

used boat with deck cut out
On a used boat with no access to the fuel tank, the deck may need to be sawed out and removed to make repairs or a replacement. Photo via Lenny Rudow.

Builders who made the effort will have installed some form of access which allows for repairing and/or removing the tank. You may need to remove fishboxes in the deck or a deck section that’s screwed and sealed with silicon, waiting for the day when work on the fuel tank becomes necessary. Getting to the tank can be a substantial job, but not nearly as substantial as cutting out the entire deck.

fishbox fuel tank access
In this case the fishbox could be lifted out to access the fuel tank, clearly in need to repair, by removing screws and caulk around the perimeter. Photo via Lenny Rudow.

Stuffing Boxes

In inboard boats, changing the packing in a traditional stuffing box is a chore that needs to happen every few seasons, and the packing gland itself will probably need to be tightened even more often. But builders sometimes install items above or around the stuffing box in ways that make it difficult to access. If you’re looking at a used boat with inboards, be sure to take the time to dig around in the bilge and make sure it won’t be a difficult to access these parts.

Plastic Through-Hull Fittings

Plastic through-hull drains at and above the waterline are susceptible to UV degradation. A decade in the hot sun can make them brittle and easily broken. If they fail, you’ll end up seeing daylight through a hole in your hull, and that daylight may only be a couple of inches above your waterline. Unless you know the complete history of a used boat, including where it was stored and how much sunlight it’s been exposed to, there’s no telling if those aged parts are going to last for days, or decades. Can you get to every one of those through-hull fittings, to replace them if and when the time comes? Or is one or more locked away, out of reach?

Two of these three plastic through-hull drain fittings have failed, and the hoses have fallen inside the boat.
Two of these three plastic through-hull drain fittings have failed, and the hoses have fallen inside the boat. Photo via Doug Logan.

Accessing the exterior of the through-hulls is a piece of cake, but to remove and replace them it’s interior access that counts. And builders are all over the place on this count. You may find it easy to get to each and every through-hull, or you may find that it’s utterly impossible to do so without disassembling the entire boat.

Steering Systems

Today’s digital electric steering systems are a world apart from cables and hydraulics, but the vast majority of the used boats for sale today still have the older systems aboard. Whether the boat you’re looking at has cable steering or a hydraulic system, make sure you’re going to be able to access the most important parts of it. Can you get to both ends of the hydraulic lines? Can you adjust  your cable system easily? Are there chafe points to worry about? Thoughtful builders will usually install a “messenger” line in the belowdeck rigging tubes to make the job easier in case new hydraulic lines or cables need to be pulled through inaccessible spaces, but not all do. Also inspect hydraulic pump mounting locations, which are sometimes so tight they’re virtually impossible to work in.

Bilge Pumps

Bilge pumps don’t last forever, and obviously, they’re a critical piece of equipment. Yet some builders will locate them deep in the bilge where you’d have to be a contortionist to reach them. Amidships and forward bilge pumps are occasionally hidden under panels or trap doors where you may not even realize they exist. And in some cases they’ll be beneath “access” ports so small you can barely fit your hand through, much less see into when your arm is buried deep inside trying to turn a screwdriver.

bilge pump in a used boat
Bilge pumps are often hidden deep in the belly of the boat, and aren’t always easy to access. Photo via Lenny Rudow.

Better builders know they’ll mount bilge pumps in specific places (like the farthest aft, lowest point in the bilge) and as they design the boat they make sure to provide a way to easily access them. Additional pumps that may be hidden get clear markings or labels on access points. At the very least, there’s a way to reach the sides of the hard-mounted pump basket, which on most modern pumps has snaps or clips allowing you to pop out and remove the pump itself for service.

When you’re looking at used boats, be vigilant about these things. None of this is meant to scare you away from a buying a used boat that you really think is right for you. Almost every boat is home to a few access problems. Just don’t let them surprise you, and if you see a ton of them in one boat, then factor in the time and expense of dealing with each of them if and when the time comes.

Want to learn more pitfalls to be on the lookout for when you’re buying a used boat? See our 10 Mistakes to Avoid when Buying a Used Boat article and video. For more comprehensive boat buying information check out How to Buy a Boat: The Complete Buying Guide.

Editor’s Note: This article was originally published in March 2016 and updated in February of 2023.