Sea trial checks for motorboats

23rd November 2021 Elena Manighetti

Sea trial checks for motorboats

When buying a used boat, you’ll want to organise a sea trial, a sort of test run, to make sure everything works as it should. Most marine surveyors will suggest carrying a sea trial out. However, not all boaters want to employ a surveyor.

We’ve put together a list of essential checks to help you evaluate the performance of the boat you’re buying on your own. Even if you do end up hiring a surveyor, being able to spot some of these issues will allow you to highlight them to the expert and ask for their opinion. Even the best engineer can miss a detail or two.

Before the sea trial

If you can, arrange the sea trial on a day with average conditions (not on a windless day void of swell) and ask the owner to stay out for at least a couple of hours. This way, you’ll be able to see the boat perform in real-life conditions. Any boat can do well on a calm day.

Ask the owner to use the boat in the same way you’ll be using it, if possible. For example, take a friend water skiing. Note down performance targets for the boat or the engine, so you can test them on the day under various loads and in different situations.

If it’s your first time buying a boat and you don’t want to use a surveyor, ask a friend to take you out on their boat and show you how a well-maintained boat should perform first. Even better if they can come to the sea trial themselves.

Bear in mind that most sea trials happen on a nearly empty boat, as the owner took most of the gear off and the tanks are low. If you can, take your family or friends with you to add some weight on the day. If you can’t, bear in mind that the performance of the boat will be less good once you have fuel, gear, and passengers on board.

Essential sea trial checks

On a sea trial, you’ll want to:

  1. Make sure the engine alarms work 

  2. Record engine hours before and after the trial to test the meter

  3. Turn on the engine from cold, without shore power, so you can spot any problems

  4. Ask the owner to let you drive the boat

  5. Test performance targets

  6. Check the engine trim and ask the owner to adjust it, if needed

  7. Cross waves or wakes at varying speeds to test the comfort of the vessel

  8. Perform a hard turn and see how the boat responds

  9. In no-wake zones, centre the wheel and see if the boat keeps its line

  10. Listen for vibrations that can indicate a problem

  11. Move around the boat while underway to see how difficult it is

  12. Pay attention to how the boat sounds at all times

  13. Check that all instruments work while underway

  14. Turn off the genset to test the alternator’s output

  15. Keep a close eye on the engine’s temperature and oil level.

If the owner allows you to, ideally you will also want to:

  • Run the main engine(s) at 80% load for an hour

  • Operate the main engine(a) at 100% load for 10 minutes

  • Perform two full lock-to-lock turns at 1,200-1,500 rpm

  • Operate the get-home system at 80% load for 15 minutes or more

  • Perform a reverse test.

You will also want to get a good feel for the boat. Notice how you sit when underway - do you need to brace yourself a lot? Can you easily reach the floor with your feet? Are the seats comfortable? Check if the storage available is enough for your needs and if there are enough handholds around the boat.

When you get back to the dock, take a final good look at everything. 

  • Do doors, lockers, and hatches open and close correctly?

  • Smell the various compartments to verify any leaks

  • Do the bilge pumps work?

  • Look for scratches, cracks, or chips

  • Is there water in the bilge?

  • Test all gear on board, including the generator.

A sea trial won’t reveal all the secrets of a vessel, but it can highlight some major problems, which in turn helps you avoid making a big, expensive mistake. Don’t skip this crucial step in the boat-buying process. 

You can’t expect a used boat to look and feel like a new one, though. Account for some fixable issues to come up sooner or later. Minor problems won’t have a significant impact on the price of the vessel, so try not to get too caught up in the details.


Download the Deckee app from the App Store or Google Play to plan and log your next boating trip. Look up points of interest on the map, check the weather forecast, and find your heading.