In my capacity as a Marine Surveyor, I am often asked, “What’s a sea trial?   And do you think we need one with a pre-purchase survey?”

To address the first question:   A sea trial is a ride in the boat, whereby the surveyor is a passenger; a very busy passenger.  The surveyor is not aboard for a pleasure cruise.  Rather he/she will be directing the pilot to perform a series of maneuvers to demonstrate critical functions of the boat.  All the while, the surveyor is observing a variety of check points, and taking notes.  It may not be apparent to the pilot or others aboard the boat during the sea trial, that the surveyor is doing much.  But trust me……..  The surveyor is watching and listening to multiple checkpoints at any given moment.



The surveyor will check a variety of items, even before the engine starts.  If he/she hasn’t done it already, then now is the time to check all fluid levels of the engine(s) and transmissions, making note the existence and quantity of any fluid leakage in the bilge.

Then the engine(s) is started.  Right away, several observations are made.  Was it difficult to start?  How fast does the starter crank? Is it smoking more than normal?  Is it pumping water?  Is the alternator working?  What’s the oil pressure?  What’s the idle RPM?  How’s it sound?

At this point the surveyor might ask to take the helm for a moment, prior to casting off.  He/she may feel the shift lever going briefly in/out of forward and reverse, and turn the helm from port to starboard; all the while listening and feeling the operation.

If the boat has a generator, the surveyor may ask to start it up, and begin testing air conditioners, and appliances.  Most likely, the generator will not be started until after the engine(s) have been started, and it will be left running with a load applied, such as an air conditioner, during the remainder of the sea trial.







Under direction of the surveyor, the pilot will begin driving the boat.  All the while, the surveyor will be looking over his/her shoulder at the instruments; checking both helms if more than one is present.  Then, periodically the engine cover will be raised to observe the engine.  The surveyor is making note of the oil pressure, voltage/amperage of the alternator output and temperature at the helm, while noting any vibration and unusual sounds, condition of the exhaust, and over all attitude of the boat as it moves through the water.


The ride will be conducted at a variety of engine RPMs, as the surveyor continues to take notes.  If the boat has an inboard engine, he/she will probably scan the engine and exhaust manifolds with an infrared thermometer, while underway.

Engine RPMs will be noted at wide open throttle position(s) as the surveyor listens and observes.  The speed will be checked with a GPS, against the helm speedometer (if present).

It should be understood from the onset; the boat will most likely be run harder under direction of the surveyor, than the owner or buyer would ever run it.  But, it should also be noted that it will not be abused.  By that I mean it will not be expected to perform beyond the design specifications of the original manufacturer.   The surveyor will most likely order a back-down test, and a variety of maneuvers.   After all……    You, as a buyer or owner are expecting the surveyor to give a statement at the end of the trial, indicating whether or not you can trust the boat to bring you back home.









If you are doing a pre-purchase survey, my answer is always “Yes”.  As a potential buyer, I recommend looking at the boat from every aspect, before you own it and become responsible for repair costs, from your pocket.

If you are doing a re-insurance survey, and you are familiar with the boat, then I leave it up to you.  Most folks calling me for a re-insurance survey are not really interested in the actual survey, beyond satisfying the conditions of the underwriter for a policy renewal.  If the underwriter doesn’t require it, then the boat owner usually doesn’t want it, in an effort to hold down costs.  Of course a sea trial could be beneficial, and save some “grief” in the future by uncovering a potential problem.  But, there is the additional cost issue of the sea trial, which is over and above the basic re-insurance survey.

This short article is not intended to train you as a “sea trial expert”.  It has merely been a brief overview, touching only on highlights of the procedure.  A sea trial is not a “joy-ride.”  Coolers and fishing gear are left on the dock.   The pilot and surveyor are kept busy throughout the sea trial, and the boat is continually under scrutiny.  Typically, there is much crew activity throughout the trial, as engine hatches are raised and test equipment is passed from hand-to-hand.  Time seems to pass quickly during a sea trial, as the checklist is long, and quarters are usually cramped.

A sea trial provides an opportunity to test aspects and functions of a boat that cannot be performed in a basic “in-the-water”, or “out-of-water survey.”

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