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Sea trials: the method behind the madness

Conducting a comprehensive sea trial is essential when buying a new or used boat. Do it right and you’ll obtain the data you need to purchase with confidence or move on. Do it wrong and you might end up buying a boat that’s a bad fit for you and your family.

Running full speed and hard rudder aboard a 58-footer. If the boat is well balanced, it will heel in a turn so that you fall neither inboard nor outboard.

A proper sea trial requires active, critical and observant participation on your part. It’s not a just a boat ride; there’s a method to the madness you have to follow to get the best results.

Last month I went over what to look for in a dockside inspection. This month I’ll give you some guidance about what to look for during a sea trial and assist you in analyzing what you observe. What follows is a checklist to use on your next sea trial. (E-mail me through my website if you want an electronic copy, Type it up as a template, leaving plenty of space between each bullet point to write legible notes in longhand when you’re out on the water. When you get back in, type your notes right away. Doing so will force you to pay attention and analyze what you’ve just observed.
I usually only gain a clear idea of what I think of a boat after I’ve written about it subsequent to a sea trial. The process of writing adds clarity and context that lets you more easily identify the relative strengths and weaknesses of a particular boat. It will be helpful even if you have some pretty big gaps in your boat knowledge. As a consultant who has done hundreds of sea trials, I’ve found that writing up my notes is especially useful when I’m asked to do direct quantifiable comparisons between boats.

Getting started
Before the sea trial, go to Radio Shack and buy a sound-level meter to measure and compare noise levels in the saloon, staterooms, cockpit and on the bridge. Pack a stopwatch to time turns and bring a handheld GPS so you’ll know how fast your boat really is at cruising speed.
In addition, a small digital camera is vital to provide a visual record of what you observe. It’s impossible to notice everything at first glance, so a photographic record is important. I usually take well more than 100 images during a sea trial and the point of a given photo might not be obvious at first. A trick I’ve learned is to write a clarifying note in my notebook. For example, the note might say I can’t see the compass from a specific position. I’ll take a photo of the note and then a photo of the compass so they’re in sequence. I always learn a lot about the boat when I’m back in my office studying the photos.
Among the benefits of taking lots of pictures is the ability to accurately record the angle of heel in hard high-speed turns. As long as the horizon is visible, all you have to do is take a picture looking forward or aft. Then you can use a protractor to accurately measure the angle of heel when you get home.
Here’s an example of why recording heel with a camera can be an important part of a sea trial. Some builders put pod drives in boats originally designed for inboards. The center of transverse lift (steering force) of a pod drive is lower and the force much stronger than that of conventional rudders, so the boat will tend to heel more in a hard turn at speed. I take pictures of pod boats operating at high speeds and accurately compare the heel angles to what it would be on similar inboard-driven boats.
A camera is also a great way to record semiplaning inception speed, which you can see when you have a clean wake astern. In quick succession, take pictures of the GPS, tachometer and wake at various rpm settings. A camera can also assist you in ascertaining the practical effect on speed and visibility forward when using trim tabs or interceptors.
Try to conduct your sea trial on a windy day in fairly rough conditions. Otherwise, you may be disappointed in the vessel’s rough-water capabilities after taking delivery. If the bottom is bare fiberglass or has been freshly cleaned and painted, the fuel tanks are less than full, and only a few people are aboard for the sea trial, make sure to deduct an appropriate amount, possibly several knots, when calculating your own real-world cruising speed and range at a given rpm with a full load. You also lose speed due to aerodynamic drag from plastic side curtains and tuna towers, especially running into the wind. In such a case, the relative wind speed may easily be double the hull speed, which means aerodynamic resistance is quite high. The engines should turn their fully rated speed at full load, a little over that with a clean bottom.
You’ve got your checklist, a notebook, a decibel meter, a stopwatch, a handheld GPS and a small digital camera, so here’s what you should look for during your next sea trial, starting at the helm.

Sorensen has done hundreds of sea trials on vessels ranging from runabouts to guided missile cruisers.

Helm station
• Are the instruments and controls easy to reach, correctly angled for your height of eye and clearly visible when standing and sitting at the helm?
• Can you read the gauges and electronics displays in bright daylight?
• Is the console for monitoring the boat’s systems clearly visible?
• Can the fire-suppression system be monitored and activated?
• Do the engine-shift controls operate smoothly and have positive mechanical detents so you can feel the control shift?
• Do the throttles move smoothly and stay set where you leave them?
• Can you drive with one hand on the wheel, leaving the other on the engine controls?
• Are trim-tab controls within easy reach adjacent to the engine controls and do they have tab-angle indicators?
• Is the searchlight control accessible with your left hand if the throttles are operated with your right hand? It should be.
• Is the steering easy and responsive, with no more than three or four low-effort turns lock-to-lock? Faster boats that cruise above 30 knots should be more nimble than slower boats. With three full turns lock-to-lock, a half-turn of the wheel should produce immediate results. Five or six turns means a 30-knot boat is less nimble than it should be.

The bright white helm makes unlighted objects hard to see at night, but the electronics placement and T-top piping make for a well thought out design.

• Windshield mullions, radar arches or drawn curtains shouldn’t create an obstruction more than 3 inches wide. Does the radar arch or anything else restrict visibility abaft the beam? If so, horizon visibility is reduced, decreasing your situational awareness.
• When seated or standing at the helm, do you lose sight of the horizon because of bow rise while getting up on plane?
• How close aboard can you see the water when you’re seated at the helm?
• Does the boat have a Euro-style deckhouse that obscures visibility? Find another boat if you have any doubts as to your ability to see all around you. A vessel closing in on a steady bearing, especially at night, may not be visible behind that radar arch or window treatment until it’s too late.
• When backing into a slip, is all-around visibility from the helm acceptable, and can you see and communicate with your deck hands?
• Back at the dock at night, do the helm electronics and gauge and switch lights interfere with night vision?
• Is windshield glare from sunlight or night lighting a problem? For example, glossy white helm areas will greatly accentuate windshield reflection.
• Do the windshield wipers sweep enough of the area you look through? Are there washers to clear salt streaking?

This Boston Whaler provides excellent visibility through its canvas-free deckhouse.

Performance, ride and handling
• Does the boat track well in following or quartering seas? It should run straight with little helm input in those conditions.
• Does the boat slow down and speed up excessively in a seaway?
• Is the boat seakindly, with no snap or deep roll in a trough or when the sea is broad on the bow?
• Does the boat need trim tabs to quickly get on plane?
• Are the tabs/interceptors so large that they can stuff the bow in a following sea? This is not necessarily a deal-breaker, but it does mean you’ll have to pay attention to the tab setting when heading down-sea.
• If the boat is equipped with multiple engines, how fast will it run on one engine without overheating?
• When averaged over reciprocal runs with and into a current, how fast is the boat at various rpm? Use your GPS to record the boat’s speed.
• When running into a sea without using trim tabs, is the ride smooth and dry?
• At what speed will the boat semiplane and leave a clean, solid wake astern? A well-designed 30-foot outboard boat can do this at 12 knots and an inboard can do this at 11 knots, assuming there’s moderate bottom loading. If you are still dragging the bay along with you at 14 or 15 knots, you are on a boat with low-speed limitations and high bottom loading.
• At what speed does the boat start to pound and shudder and become uncomfortable? Generally, a well-designed 20-foot boat should be able to run at 25 knots in a 1-foot chop without pounding. A well-designed 26-footer in 2-foot seas should not pound, nor should a 36-footer in 3-foot seas or a 50-footer in 4-foot seas.
• Have someone else take the wheel. Now stand 6 inches away from a table or other fixed object, facing athwartships. At cruising speed, have the person driving put the rudder all the way over. If your body is the same distance from the object in the turn as it was when the boat was running straight, you have a true turn, like riding a bike, which makes the boat safer. If you have to lean toward or away from the object to keep your balance, your passengers will be less steady on their feet.

• Does a twin-engine boat turn just as quickly in both directions? Use a stopwatch to time a 720-degree hard turn at cruising speed in both directions. If the boat does not make the turns in the same amount of time, then the steering is set up unevenly. Look for a 30- to 35-second 360-degree turn in a 25- to 30-foot outboard or sterndrive and a maximum of 45 seconds in an inboard to 55 feet. If an inboard boat takes longer than that to turn, it may need larger rudders, or the stops may be set short of the correct 35 degrees. Another possibility is that you’re driving a full-keel boat — or maybe an electric pontoon boat.
• In a single-engine boat, is the steering responsive enough for safe maneuvering? How well does the boat back and fill around the harbor? Can you dock it, including backing into a slip, without using a bow thruster?
• Whether you’re driving a twin- or single-engine boat, can you back down with control and with the stern going in the intended direction? Can you back the boat downwind?
• If the boat is fitted with a bow thruster, is the thruster effective in a crosswind or crosscurrent?
• Do the engines shift smoothly at idle? Will the boat run slow enough when the engines are clutched in at idle? Trolling valves may be needed on high-powered boats.
• If trim tabs are fitted, do they quickly produce a noticeable difference in trim and correct for heel and list at speed? Will dropping one tab correct for a 20-knot beam wind? If the boat keeps picking up speed until the tabs are lowered all the way, that’s a good sign they are too small. Full tabs should immerse the bow enough to slow the boat and even start it yawing about its heading, known as bow steering.
• With one engine shut down, can you turn in the direction of the running engine?

A 30-foot outboard dual console on plane at just 11 knots - this bodes well for the boat's get-home capability in rough water.

Quiet and comfort
• Are noise levels acceptable at cruising speed? Look for a maximum noise level in the low-80-dBA range. Levels in the low-70-dBA range throughout the interior are ideal. If your boat’s saloon is in the mid- to high-80-dBA range, plan on wearing earplugs on long trips. I ran a whisper-quiet Tiara 5800 that measured just 73 dBA in the saloon, which was even quieter than an Alden sedan or a Riviera coupe.
• Can you move around comfortably with someone seated next to you at the helm?
• Are vibrations around the cockpit or aft deck abnormally high? If they are, it can be an indication that prop repair or balancing is in order.

Anchoring ease
• Anchor the boat. Can you control the windlass from the helm? Can you speak directly to the people on the bow from the helm? Can you see the pulpit from the wheel?
• Can the anchor be deployed from its chute/pulpit by gravity alone without coaxing?
• Does the anchor hold when you back down at high idle?
• Is there plenty of storage for the anchor line, and can the anchor be secured while under way?
• Is a washdown provided for the anchor, chain and line?
• How much anchor line/chain is there? Divide the total length of the rode by six (more or less depending on how much chain you carry) to calculate the maximum depth of water you should anchor in. Of course, the maximum safe depth for anchoring depends on such factors as wind, current, nearby hazards and whether you will be anchored overnight.

On deck
• Do you feel secure walking forward? Are the rail height and the side-deck width adequate? How about the non-skid?
• Are the bow rails 30 inches high, essentially unyielding to the touch and plumb with the deck’s outer walking surface? If they are any lower, the fulcrum created when you lean against the rail makes it more likely you’ll end up swimming.
• If centerline access to the foredeck is provided, are the steps large enough to negotiate safely, and are there rails to hang on to as you make your way forward?
• Are there sufficient cleats, and are they large enough for standard mooring lines and a couple of storm lines? At a minimum, the boat should be fitted with two bow, two stern and two spring-line cleats.
• Do cleats and chocks provide a fair lead to the cleat, avoiding chafing and cutting points?
• Do you have to stuff the line through a hawse hole to reach the cleat? This is a silly, inconvenient and potentially hazardous design for a pleasure boat. A simple gunwale-mounted cleat eliminates these problems.
• Can you reach the stern cleats without leaving the cockpit? If you have to go back to the swim platform near the props to get to the stern cleats, someone has screwed up the design.
• Can you deploy the boarding ladder from the water in the event you fall overboard while on board by yourself?

• Do engine exhaust fumes get sucked into the cockpit when the boat is running at speed by the station wagon effect (a low-pressure area inside the cockpit created by airflow past the boat)? If exhaust fumes do get sucked into the cockpit, ask yourself if that’s something you want to live with.
• Are exhaust noise levels acceptable (mid-70 to low-80-dBA range)?
• Do you feel safe walking around the aft end of the cockpit at cruising speed?
• Do you feel safe walking around the rest of the cockpit at cruising speed (consider the height of the coaming or railings, the non-skid surface and hand-holds) or do you have to crouch or crawl around back aft?
• Does the transom door stay securely latched?
• Does the boat have a wet ride, making the cockpit unusable at cruising speed?
• Is access to the flybridge safe via comfortable stairs or a ladder with railings, large treads and at least 20 degrees of slope? Are the bridge rails at least 30 inches high, preferably 36, all around?
• Is there enough seating to meet your needs?
• Do cabinet doors and drawers stay closed in rough water and during hard turns?
• Do hatches, doors and other components rattle?
• Is the stereo usable at cruising speed?
• Is at least one cabin hatch at least 20 inches across, big enough for the largest member of your family or crew to fit through? It’s there for emergency egress, as well as to let in daylight and fresh air. Is there a ladder or step (like a berth or table) to help you climb up and through the hatch?
• Are there sufficient grab bars and overhead grab rails in the saloon and cabin?

The easy access through the deck-level side door on this MJM 40 is a smart feature.

A sea trial is a thorough examination of the boat’s systems and performance while under way. If you want your money’s worth, make it a search for reasons to buy or reject the boat. Don’t let the curves and glitter captivate you. Remember, you are responsible for the safety of your family and friends; they are responsible for their own enjoyment. Use the sea trial as chance to make sure you’re buying the boat that’s right for you. Study the above checklist and bring it with you. Good luck, and let me know how it goes. Happy trials!

Eric Sorensen is a consultant to boat- and shipbuilders, boat owners, and to the government. He was founding director of the J.D. Power and Associates marine practice and is the author of “Sorensen’s Guide to Powerboats: How to Evaluate Design, Construction and Performance.” Eric can be contacted through his website,

This article originally appeared in the April 2012 issue.


A good turn of speed is one of the advantages of planing hulls. (A Beneteau Barracuda 9 is shown.)

How different hull types react in rough water

Displacement, semidisplacement and planing hulls all have their pluses and minuses. We compare and contrast them.