The Trial Run

A boat at the dock is a boat with its best foot forward. The trial run is where it has to actually work, and it routinely produces findings that no amount of static inspection would have found.

What Gets Tested Underway

Starting behavior from cold where possible, idle quality, response through the range, performance at cruise and at wide open throttle, shifting in both directions, steering through full lock, and how the vessel tracks and handles.

Also the things that only appear under way: leaks at the shaft seal under load, exhaust behavior at temperature, vibration signatures, autopilot function, and whether the bilge stays dry when the boat is working.

Engine Performance and Temperatures

Operating temperatures logged across the range, and whether the engines reach and hold their rated wide open throttle revolutions. An engine that will not reach rated revs is telling you something, usually about propeller pitch, a fouled bottom, or the engine itself.

Smoke color and behavior at start, under load and on deceleration are recorded. Oil pressure, charging output and any alarm behavior get noted.

What this does not replace is an internal engine assessment with oil analysis and a borescope. A trial run tells you how the engine behaves. A mechanic tells you what is going on inside it, and on a high-value or high-hour vessel you want both.

Steering, Handling and Vibration

Steering is run lock to lock and assessed for play, effort and any binding. On hydraulic systems I look for a soft or spongy feel that indicates air or a failing seal.

Vibration is one of the more useful diagnostics available on a trial run. A shaft, coupling, bearing or propeller problem announces itself under load in a way it never does tied up, and the speed at which it appears narrows the cause considerably.

Who Should Be Aboard

The vessel needs somebody authorized to operate it, usually the owner or a broker, because I am there to inspect rather than to take command of somebody else’s boat.

Come if you can. Watching the boat run, with the person assessing it standing next to you, is worth more than any paragraph I can write about it afterwards.

Preparing for the Trial Run

Fuel enough for the run, batteries charged, the bottom reasonably clean, and safety equipment aboard. If the bottom is heavily fouled the performance numbers are meaningless, and I will say so rather than write them down as if they meant something.

Where a haul-out is happening the same day, the boat comes out of the water first. I want to see the bottom, and I want it cleaned, before anybody runs the engines up.

Two reasons, and I have run into both. Propeller nuts missing — do a backdown test on that and the propeller can leave the shaft. And a bottom under heavy growth after being told the diver came last week. Performance numbers taken over a fouled bottom will not tell you anything about the boat.