The dockside survey is theory. The sea trial is reality. This is where engines overheat, vibrations appear, and "minor" issues become deal-breakers.
1. The Pre-Trial Briefing
You are an observer, not the captain. Never drive the boat. If you crash, it's your fault.
The Speech: "Captain, I need you to operate the vessel safely. I will ask for certain maneuvers (WOT, hard over), but only perform them if you deem it safe. You are in command."
2. Cold Start (Critical)
Arrive early. Touch the engine blocks. If they are warm, the seller has pre-warmed them to hide starting issues or smoke. Start the engines yourself (or watch closely). Look at the exhaust.
- Blue Smoke: Burning oil.
- White Smoke: Steam (overheating) or unburned fuel (injectors).
- Black Smoke: Overloading / air starvation (turbo issues).
3. The WOT Test (Wide Open Throttle)
An engine that cannot reach its rated max RPM is an overloaded or damaged engine.
The Procedure: Run at WOT for 3-5 minutes (if temps allow).
What to Watch: Temperature gauge creep. Does it stabilize or keep climbing? If it climbs past 195F/200F, back off immediately.
4. Steering and Handling
Take the helm (briefly) to feel the hydraulic steering. Is it spongy (air in lines)? Does the boat track straight? perform a "Hard Over" turn at speed. Does the rudder shudder?
5. The Back Down Test
Put the boat in reverse. Does the transmission "clunk" hard? Do the engine mounts jump? This tests the drivetrain under opposite load.
Conclusion
The sea trial proves the vessel's fitness for purpose. A boat that looks perfect at the dock but overheats after 5 minutes is not a seaworthy vessel.