Sea Trials .. beyond a boat ride!

Sea trials important part of Marine surveys

Beautiful sunny day, blue skies, nice breeze in the air and inviting smell of the ocean. And you are excited that you are about to have a sail with the boat which soon to be yours. Sounds awesome, isn’t it… But a sea trial should go above and beyond a nice boat ride.

Conducting a comprehensive sea trial is essential when buying a new or used boat. If it’s done right you’ll obtain valuable information you need to purchase with confidence or move on. With a poorly performed sea trial, you might end up buying someone else,s problem or a boat that’s a bad fit for you and your family.

A proper sea trial requires thorough planning and constant observation, measurement, testing, and recording. It’s not just a boat ride; there’s a method that has to be followed to get the best results.

On the sea trial, not only is the engine and overall vessel performance evaluated, we test the steering, controls, shafting, engine mounts, and exhaust systems, but we also examine structural hull elements while under load. In addition, all hull fittings, rigging and sails, and instruments will be tested for functionality and serviceability. Electronic equipment will also be tested for accuracy where possible.

We always recommend the sea trial to be performed by an accredited marine surveyor and/or by a certified mechanic. But in some cases, your budget or other limitations may not give you the chance to hire a surveyor or mechanic for the job. If you choose not to have the surveyor or mechanic attend sea trial, at least you will have the benefit of knowing any potential issues revealed by those inspections if they have been performed during the sea trial.

I would like to provide you with some recommendations if you are planning to perform the sea trial by yourself;

Before the sea trial

– Check the weather forecast and plan your sea trial date accordingly.

– Keep the additional “riders” to a minimum. A crowded vessel will make the sea trial less safe, harder and more complicated.

– Be sure there will be a qualified person to drive the boat. You shouldn’t operate the boat. Not only for liability reasons also you will be busy with making observations, measuring, testing and taking notes.

– Make a sea trial plan (list of tests, manoeuvers etc.) and discuss your plan with the owner and or captain beforehand.

– Ask the owner, captain or broker not to warm up the engine before you get there. You can learn a lot from a cold start, the most basic observation is how hard the engine is to start. Great opportunity to observe for weak batteries and other potential problems.

– Check the bilges (bilge water level, presence of oil, etc.) and compare them with how they look once you’ve returned to the dock. Taking before and after pictures would be helpful.

– Check and record engine and generator hourmeters.

– Check the engine oil and coolant levels, as well as the transmission oil level, before and after the trip, confirming correct fill levels and note changes that could indicate leaks.

– Check and record all fuel and water tank levels. Be sure they are at least half full. That you may observe possible leaks as well as observe the performance of the boat propulsion under load.

– Place a clean drip cloth under the engine, transmission and the generator before getting underway (which makes oil leaks are more noticeable)

– Suggested tools to have for a sea trial; Stopwatch, digital camera, voice recorder, sound level meter, Handheld GPS (A smartphone with the proper apps can perform all of these tasks) IR Thermometer, multi-meter, strobe light, binoculars, notepad, and pens.


– Check all engine and bilge alarms before you start the engine.

– Record oil pressure, temperature and voltage output for the engine at various speeds (slow throttle, half, full, and cruising speed).

– Record boat speed at various throttle levels (slow throttle, half and full)

– Inspect stuffing boxes, drip-less shaft seals, and rudder glands for leaks. It’s not unusual for these to be dry at the dock, but leak while the vessel is underway.

– Check the shaft for vibration at various speeds. If there’s a visible wobble, you can get a rough idea of how bad the problem is by touching the top of the gearbox. If you can feel it there as well, the issue needs to be corrected sooner rather than later.

– Note the engine manufacturers maximum recommended RPM and after the engine has warmed up a bit, ask that it be run at full throttle for a short distance. Observe and record boat speed, engine room, heat exchanger, transmission temperature. Also look for any unusual sights and sounds-burning smells, smoke, vibration, excessive owner/broker sweating, etc.

– if there is a generator run the generator and have all systems run, stove/water heater/air conditioning, etc. Observe and record accordingly.

– Perform a back-down test which can be done by reducing the throttle quickly while shifting from cruising speed to neutral, then to reverse, then increasing power. Observe the engine mounts and driveshaft simultaneously.

– Perform Figure-eight turns at cruising speed. These manoeuvers are useful to verify maneuverability, handling and that the vessel has an equal turning radius to port and starboard. Observe and record steering gear, rudder shaft and packing simultaneously.

– On a sailboat; Raise all sails and inspect each for condition (repairs, damaged threads, chafe, etc) as well as ease of raising and lowering. Make a couple of tacks to see how the boat handles. Observe the running rigging accordingly.

Back at the dock;

– Check and record engine and generator hour meters as well as fuel and water tank levels.

– Check and record engine oil and coolant levels including the transmission oil.

– Check and take pictures of the bilges and the drop-sheets you have placed before sea trial.

In my opinion sea trials should be performed after a survey, not before. Most of the times the survey will produce clues that may not be determined unless the system or structure in question is put under load. Performing the sea trial afterwards gives you a chance to follow up on those clues.

If you would like to learn more about sea trials here is Germanischer Lloyd Guide For Sea Trials of Motor Vessels

Share this post


Leave a Comment

Your email address will not be published. Required fields are marked *