Actually performing a sea trial correctly is quite an involved session if done correctly below is a general guideline
NOTE:Begin by ensuring the vessel is ready to go to sea, especially if she’s been dockside for some time,Safety gear on board is essential,
Firstly: Conduct a dockside, visual inspection of the vessel’s key systems, particularly running gear, including the engine and transmission fluids, stuffing box, gearshift and throttle components, shaft coupling, exhaust system, and steering gear. Be sure to look under engines and generators and note any oil/fluids )
1) Trials should be conducted with the vessel in its typical cruising trim, which means the engine room hatches and doors should remain shut at all times,
2) When you arrive at the vessel for a sea trial the engines should be cold, not having been run for at least a day.
3) Tanks, fuel, water, and waste should be at least half full. Ideally, fuel and water should be full.
4) Ensure that engine alarms operate. Typically, this can be done by turning the keys or ignition switches to the “on” position without starting the engines. A low oil pressure alarm should chirp or sound continuously
5) For pre-purchase sea trials, in advance of the established trial date ensure that a qualified individual, typically the broker or a designated captain, will be present to operate the vessel.
6) Each and every system that could or might ever be operated while under way should be operational and should be checked. This includes, obviously, main propulsion engines; however, it also includes the wing engine and the generator.
7) Engines should be cycled through gear positions several times to ensure proper operation of controls and transmissions. Additionally, a back-down test should be performed
8) Generators should be run, while under way, to at least 50 percent and preferably at or above 80-percent load.
9) Include in the “run list” water makers, and of course, all navigation electronics, radar, depth finders, plotters, etc.
10) One of the more important and often overlooked aspects of a sea trial is temperature monitoring, specifically the temperature of the air being drawn into the engines and generators.
11) If she’s a vessel that’s designed for blue water, offshore passage making, then she should be tested in offshore conditions to the extent possible.
12) If the engine aboard the vessel you are sea-trialing is capable of providing load and fuel consumption information, make a note of this at each rpm increment.
13)During the 60-minute, 80-percent run, periodically visit the engine room to take temperature readings of the aforementioned components as well as the following:
• Alternator casings: These rarely exceed 200°F.
• Coolant expansion tank: This should be roughly the same as the dash gauge, rarely above 195°F.
• Transmission: Most rarely exceed 160°F although some, such as Detroits, will run as hot at 180°F. It’s best to get a spec from a dealer or the manufacturer. An overheating transmission can be a sign of worn clutch discs, a fouled cooler, or improperly adjusted controls.
• Oil temperature: This should be measured at the middle of the oil pan. Typically at this load it will ideally be roughly similar to coolant temperature, and as high as 220°F. Higher than this temperature leads to increased oxidation and shorter lubricant life. In short, it does no good, while anything under about 160°F will cause varnish and sludge build up, which in turn could lead to eventual oil starvation of bearings, rings, and valve trains.
• Thrust bearing: For vessels so equipped, the acceptable temperature is dependent upon the manufacturer. For one of the more popular brands, the range for the thrust bearing itself (don’t confuse this with the CV joint) is approximately 120°F to 160°F. Anything above this often indicates an alignment issue.
14)At the conclusion of the 60-minute, 80-percent run, check and record the temperature at the engine air intake. Now you are ready to move on to the 100-percent throttle run. Advance the throttle to its maximum position, while monitoring the tachometer. The engine should reach the wide-open throttle rating established by the manufacturer and slightly more(100% run for 10 minutes). For instance, an engine rated at 2500 rpm should attain 2500–2540. The slight overage allows for weight that almost certainly will be added to the vessel. If an engine fails to reach its full rated rpm, it’s failing to meet the manufacturer’s installation specifications and it’s also an indication that it’s overloaded. Overloading an engine never bodes well and in severe cases it can lead to serious damage. Slightly under loading, on the other hand, by slightly over-revving, ensures the engine is in a safe rpm zone. If the engine exceeds the rated rpm by too much, that’s undesirable as well. While it won’t cause any damage per se!, it means the engine is failing to provide the horsepower it was designed to produce, and you are paying for more engine than you are getting until it’s corrected. Once again, ideally it should reach rated rpm and just slightly more.
15) If after three or four minutes the engine fails to achieve its rated rpm, that is it’s either significantly under (more than 100 rpm) or significantly over (more than 50 rpm), then there’s little sense in continuing this portion of the trial as it will serve no purpose. If it does reach the proper rpm, stay the course for 10 minutes while carefully monitoring instruments for signs of overheating or dropping oil pressure. At the conclusion of this segment of the trial, return to the engine room to take another round of temperature readings and do so once again while idling back to the dock.
16) Next, conduct a steering system test. At approximately 1200–1500 rpm, execute two full turns, rotating the wheel lock to lock. During this test you or your expert should be in the lazarette or “tiller flats” area monitoring rudder stocks, tiller arms, tie rod hardware, hydraulic rams, cables, and pulleys, etc., for any signs of wear or inappropriate movement.
17) As you are returning to the dock, perform a back-down text. While motoring ahead at approximately 1000 rpm, shift to neutral, wait three seconds, and then shift into reverse, applying no throttle for at least 10 seconds. The engines should not stall. If they do then there may be an issue with propeller size, gear reduction, or simply idle rpm. Either way, such stalling is not normal and it’s not safe. Just imagine if it were to occur in a marina fairway on a windy day.
18) The trial doesn’t end when you’ve returned to the dock. While it may be uncomfortably warm, now is the time to conduct another inspection of the engine room. How does it smell? Is there an odor of fuel, coolant, burning oil, exhaust, or the telltale acrid whiff of electrical or battery anomalies? Has any fluid accumulated under the engines or generators? Is there water, oil, or fuel in the bilge that wasn’t there before?
19) The final step in your sea trial tour? Conduct an analysis of all vital fluids, engine, and generator crankcase oil and coolant, transmission fluid, and, if applicable, stabilizer hydraulic fluid.
So as you see if conducted correctly a sea trial is fairly involved.Written notes and photo's /video's are encouraged strongly, and being armed with digital tach and temp gun is essential
Cheers Steve(MIIMS-Lloyd's Maritime)NZ Chief Eng 1
Thank you CaptSteve for sharing this, a good list to go on inspection to buy a boat or check your own boat that's all OK.
