What to Look for on a Sea Trial

It’s critical to perform a sea trial before you buy a boat. This is your chance to make sure everything works properly and the boat performs as expected. And if the boat is used and you can’t afford or don’t have access to a marine surveyor, you will need to rely on yourself to perform the sea trial and learn what you can to help confirm your choice or decide not to buy. The most important things to consider include:

sea trialing a boat
Taking a boat out for a sea trial is a critical part of the buying process, whether the boat is new or used. Photo via Bob Hewes Boats.

Assessing a Boat’s Structural Condition

Obviously when buying a new boat of a reputable brand this isn’t an issue, so if you’re buying new you can jump right down to the section on sea trials below. But when buying a used boat of significant value hiring a boat surveyor is always a good idea. Assessing a boat’s structural condition requires some background knowledge, and this is where a surveyor can be very helpful. But what does a marine surveyor look for? It starts long before the boat goes in the water. Some of the basic checks include:

  • Walking around and thumping the sides of the boat with the bottom of your fist. The hull should ring with a solid whump and it should feel firm under your fist. This is particularly important in the transom area, where water intrusion typically appears first. Anywhere water intrusion is suspected, a moisture meter should be used to gather further intel.
  • Looking at the condition of the underwater gear. Is the skeg still nicely painted? Is the leading edge still straight and true or is it pocked and jagged from hitting rocks or sandbars? Are all anodes in place and in good condition? Is the prop dinged or bent?
  • Touching and testing everything. The grab rails get wiggled to see if they’re loose. Seat pedestals are checked to see if they’re still mounted firmly to the cockpit sole. Stowage compartments are opened and closed to be sure all the hinges are still solid.
  • Activating all switches, electronics, and electrical items to be sure they work. All the wiring gets a visual inspection, too.
  • Visually inspecting major components like stringers and hull-to-deck joints. If anything seems amiss, a closer inspection is warranted.
inspecting a boat propeller
Running gear and propellers should all get a close inspection. Photo via Lenny Rudow.

Checking the Mechanical Condition of Power Systems

The sea trial itself is one way you check the power systems, since it gives you the ability to observe for proper performance, listen for any unusual sounds, and feel for any unexpected vibrations. Use all of your senses. With an older boat, you may want to have a mechanic check out the systems. Beyond that, however, there are a few basic mechanical checks anyone can perform.

engine with some corrosion visible
Basic checks include a visual inspection for corroded parts. Photo via Lenny Rudow.

Pull the dipstick and make sure the oil looks clean and fresh (milky water indicates water mixed in, a big red flag). Visually inspect for signs of corrosion or age. Performing a compression check is always a good move (as a rule of thumb the results for each cylinder should be within 10 percent of each other). In the case of inboards and stern drives also smell under the engine hatch. You likely will smell gasoline to a certain degree, but anything overpowering indicates a potential fuel leak.

On-The-Water Performance

Now for the sea trial, the most important part of your intel-gathering process whether a boat is new or used. If it is used, I like the boat to be stone cold when I fire it up for the first time. If the engine’s rotating assembly is going to make any funny noises, it will be when it’s cold. If it’s an inboard or stern drive open the hatch so you can hear everything better. Does the starter engage smoothly and quietly? Does the engine rattle or knock when you start it? It should run with little more than a thrum of vibration and the hiss from the flame arrestor atop the engine.

As you back out, notice how the shifter works. Does it engage forward and reverse when the shifter is moved to the detents? Is there any binding or sticking in the shift cables? Not all signs of trouble will be deal-breakers, but it can help you develop your punch list if you decide to buy it. As you leave the dock take note of slow-speed handling, which can be problematic on some boats.

boat motoring slowly
Slow speed handling is better on some boats than others, so pay attention to how the boat maneuvers as you pull out of the marina. Photo via Lenny Rudow.

When you advance the throttle, notice how difficult or easy it is for the boat to get on plane and see if it’s something you can live with every boating day. Then once you’re up and cruising, take it to top speed. The boat should reach and hold that speed with no trouble. If you’re satisfied with the result, bring it back down to cruising speed;  3,200 to 3,500 rpm is a good rule of thumb for inboards and stern drives, while most outboards are happier running between 4,000 and 4,500 rpm. Now note the speed. Will you be happy cruising at that rate, or would you long for a faster boat? If the boat has a fuel flow monitor, be sure to note the consumption at cruise so you know just how big those fuel bills could be.

At cruising speed — in an area where it’s safe to do so — take the boat into hard right and left turns. Do slalom maneuvers then full-circle turns. The boat should hold its line without hooking, washing out, or blowing out the prop. If the boat has a stepped bottom, don’t trim it down to do these tests. While you’re doing all this, listen for cautionary squeaks and rattles. If it’s a twin-engine boat, at this point you may also want to shut down one of the powerplants and find out what your “get home” speed will be in case one ever fails.

Assessing Seakeeping Abilities

Now look for some waves to get an idea of how the boat handles the seas. If it’s calm out, look for other boats that may be creating wakes and if there aren’t any around, turn a few doughnuts to create some of your own. Try hitting waves from all angles, to get a feel for how the boat handles a head sea, a following sea, and so on. Then position the boat so that waves will hit it on the beam, and shift into neutral. Feel how the boat rocks and rolls, and make sure its stability is up to snuff.

boat hitting wakes
If the seas are calm use boat wakes – either from other boats or wakes you create yourself – to assess how the boat handles waves. Photo via Lenny Rudow.

Spend as much time as you and the seller or dealer are comfortable with out on the water. The more varied the seas you experience the more you’ll learn. Even just drifting around for a while can be illuminating.

When you’re satisfied that you have a feel for how the boat acts out on the water, cruise it back to the dock the way you normally would. Once you get back to an idle zone, go back to the engine and do another full sensory check. Many times an engine that has been warmed to operating temperature will act different from one that is still cold.

Will following all these procedures keep you from buying a boat you won’t be happy with, or in the worst case, ending up with a lemon? In reality, that’s always a possibility no matter how thorough you are. And if the boat is used there’s a good chance that it will need some work sooner or later. However, I can tell you after years of testing boats using the techniques listed above, you learn a lot about any boat this way. These methods will uncover foibles and idiosyncrasies, yes, but also will highlight — perhaps most importantly — whether you like a boat enough to buy it.

Editor’s Note: This article was last updated in October of 2022; a previous version of this article originally appeared on Boat Trader in April 2015.