How to Do a Sea Trial

This is the sixth of a 10-part series on how to buy a boat.   If you have not already seen it, check out Chapter 4 – How to Evaluate a Used Boat.

When shopping for a boat, taking a Sea Trial is an important step – especially if you are looking at a used boat.  This is because it will enable you to see how the engine performs under load, check that all mechanical and electrical systems are working properly, and see how the boat rides/handles.  It is also a good opportunity to learn how to properly operate the vessel.

With new boats, doing a Sea Trial before finalizing the purchase is also a good idea too but for slightly different reasons.  Though mechanical, electrical and structural issues should be less of a concern with a new product that is under warranty, it is still important to confirm whether the performance, comfort and ride/handling measure up to your needs and expectations.

However, many dealers and some private sellers refuse to offer a sea trial for various reasons.  I will address this later in the chapter.

When to Do a Sea Trial

Doing a Sea Trial with a boat is a bigger commitment of time and resources than test driving a car.  In most cases, you simply can’t drive the boat off the lot but instead need to trailer it somewhere (which could be a considerable distance).  Plus, depending on the location and time of year, the boat might even have to be prepped and de-winterized in order to do the Sea Trial.

For these reasons, a Sea Trial should only be done after the prospective buyer has carefully inspected the boat and intends to purchase it subject to a satisfactory trial.  In fact, many dealers and some private sellers will require a refundable deposit and a purchase agreement before agreeing to a Sea Trial.  I believe this is reasonable given the investment of time & resources and to discourage non-serious buyers or those just looking for a free boat ride.

How to Do a Sea Trial

A typical Sea Trial is done with the seller or dealer representative on-board and lasts about 15-20 minutes (longer for larger boats).  This should give you ample time to run through all the important checks and remain on the water long enough to allow any major issues to surface.

During the sea trial, the party selling the boat will likely operate it part of the time (especially when launching and docking the boat). However, as a prospective buyer, you should take the wheel as well – especially when out in open waters.  Your main goals are to determine whether you like the comfort and ride of the boat and identify any problems or issues to help you make an informed purchase decision.  Also, pay close attention to what you observe during the Sea Trial in comparison to what the seller disclosed to you beforehand (see my list of initial questions to ask the seller and other checklists here).  If there is much inconsistency, this is a major red flag and reason to caution the seller’s trustworthiness.

Tip: Before you check out a boat, go online and look up the max RPM for the engine and the approximate top speed for the boat/motor package. It would be helpful to locate the engine’s operating temperature as well. You will want to refer to this information when doing the sea trial.

Below is a sequence of checks to perform during the Sea Trial.  You can also download my complete set of checklists here to help you along the way.

Cold-Starting Check

While the engine is cold, start the engine and let it idle and then take note of the following:

  • Does it start easily?
  • Does it idle smoothly?
  • Is there any excessive smoke? (older two-stroke engines might smoke some but newer engines and four-strokes typically smoke very little)
  • How quiet is the engine and are there any unusual noises or squeals? (e.g., bearings starting to fail)
  • Is there a strong “pea-stream”? This indicates that the impeller is working properly (which is vital for engine cooling on most marine engines).  Ask the owner when the impeller was last replaced (they often need to be replaced every 2-4 years).

This is also a good time to check the bilge.   There should be little to no water in this area.  If there is, that could mean that there is a leak somewhere.  You will want to check this area periodically to see if the water level increases or the bilge pump kicks on.  If so, it will be important to diagnose where the water is coming from (missing screws, improperly sealed engine mounts, leaking hull, etc.).

Controls/Shifting Check

After the engine has warmed up briefly, carefully shift into the forward gear.  Take note of how smoothly and quietly it shifts (note: a noticeable “clunk” is common in older boats and even newer boats with mechanical shifting).

Next, return to neutral, pause a few seconds, and then shift into reverse.  It is important to note that when shifting a boat with mechanical (i.e., cable) controls, you don’t want to shift too slowly/gradually as this will cause the gears to grind as the engine goes in and out of gear.  The boat seller should show you the proper way to do this if you are uncertain.

Do this a couple times each way – making sure to pause in neutral each time.  Of course, you would like to see it shift smoothly into forward and reverse.  However, if it is difficult to shift or if there is a lot of grinding noise (when shifted properly), it could mean a problem with the shift cable, controls, fluid levels, clutch or gears.  In any case, you would need to know the cause of the issue before going forward because it could be an easy fix or a fairly expensive repair.  This is likely a good time to get a dealer or marine mechanic involved if you are really interested in the boat.

Acceleration Check

Navigate to an open and safe area on the water.  While traveling at idle speed, take note of your engine (boat water) temperature & oil pressure.   With the engine adequately warmed up, push the throttle all the way down if it is safe to do so and water conditions permit.  Note that once the boat is on plane, you might need to trim up the engine so that the boat is not plowing the water (if you are not certain of this, the seller should be able to help you).   Hold the boat at wide open throttle (W.O.T.) for a minute or two and take note of the following:

  • How long it took to get the boat on plane.  The quicker a boat planes is better for safety reasons (visibility) and is especially important if you plan to do watersports.  If it planes too slowly, that could indicate that the boat is underpowered which is a common cause of boater dissatisfaction.
  • What was the Max RPMS achieved and does this match the engine manufacturer specifications? If the Max RPMs is much below that stated by the manufacturer, this could be because it is propped incorrectly (likely too much pitch) or there is an issue with the motor. Either way, you will want to find out the cause before purchasing the boat.
  • The top speed (best to check this on a GPS fish finder or phone app, not a boat speedometer which tends to be inaccurate). If the engine is at or near the proper Max RPMs but the boat is traveling slower than anticipated, this could be due to several factors including: growth on the hull, heavy load in the boat, boat taking on/carrying water (i.e., leaking), engine not trimmed properly, excessive wind/current, etc.  Again, it will be best to figure out the reason before going forward with the purchase.
  • The (boat water) operating temperature, if available. At acceleration, the temperature might rise and then stabilize.  However, if it continues to climb or is too hot (say, well above 160F), this could indicate an issue with the engine or impeller (not forcing enough water to cool the block), a stuck thermostat, a faulty or inaccurate gauge or some other engine problem.  A typical operating (water) temperature is roughly between 120F and 160F although this varies slightly by engine.  Warning alarms typically go off between 200F-220F (water boils at 212F).
  • The oil pressure, if available. A typical pressure reading should be roughly 40 – 60 psi at W.O.T., although this will vary by engine.  If the reading is much below or above this, it could indicate a problem with the engine, oil pump, the amount/type of oil used, the age of the oil/filter or a faulty gauge.
  • How the boat handles. A boat with a poorly designed hull might “porpoise” (roll up and down) or “chine walk” (roll side to side) at speed which can make for an uncomfortable or even scary ride.  Of course, it is important to make sure the engine is properly trimmed when doing this because that could cause handling issues.

After you have ran the boat at W.O.T. for a minute or two, gradually deaccelerate to idle speed and then put the engine in neutral while the motor is still running (if you accelerate too quickly, water might come over the transom on some boats).   Examine the engine, steering mechanism (if hydraulic or power steering) and bilge area.  Look for any smoke or oil/fluid leaks.  Also, check to see if water has accumulated in the bilge which might indicate a leak in the hull or transom.

Ride/Handling Check

Before you perform this check, it is a good idea to deploy the bimini if the boat is so equipped.  That way, you can check how well it holds up at speed or whether it flaps/rattles in the wind.

From idle position, shift the boat into gear and accelerate to a comfortable cruising speed.  For most boats, this is between 3,000 to 4,000 RPMs.  Note that you might need to adjust your trim to hold the boat on plane properly at this reduced speed.  For this check, you will want to operate the boat like you normally would and try to replicate the sea conditions you might encounter. As you do this, you will want to perform the following:

  • Travel in a straight line to see how the boat handles at cruising speed. Does it track straight or want to pull to one side?  (not uncommon in smaller boats but could also indicate that the trim tab is missing or out of alignment).  Is the ride smooth/effortless or does the boat roll up and down or side to side?  Find out what the minimum speed (RPMs) to hold the boat on plane.  Boats requiring lower speeds may save you money on fuel and be more comfortable in heavy chop.
  • Take a hard turn to the starboard (right) side. Note how tight it could turn and how well the boat tracked (some will slide on the turns).  Did the engine stay steady or did it cavitate/blow out?  How was the steering effort and were there any unusual sounds coming from the steering system?  Repeat the process with a hard turn to the port (left) side.
  • Next, find some fairly heavy chop or boat waves to see how it handles in rough water. If it is a calm day and water is pretty flat, you can create your own waves by doing slow speed “donuts” (at slower speed, the hull displaces more water creating larger waves).  Swing out and then go through the waves head-on, at a 45 degree angle, and with the waves.  Was it smooth or bouncy?  Dry or wet?  It is important to note that different boat/hull styles will inherently handle waves differently.  For example, a flat-bottom Jon boat or skiff will bounce much harder in waves than a Deep V fishing boat or Cruiser.  Therefore, you need to evaluate the ride relative to the type of boat you are considering.

After completing your ride/handling check (at cruising speed), pull the throttle back quickly to idle speed.  Look to see whether water breaks over the transom.  Again, certain types of boats with very shallow hulls and low gunnels are more prone to do this so you need to evaluate this within the context of the type of boat you are considering.  If there is some wash over, it is probably not a big deal but something to be mindful of when operating the boat.

Slow Speed Maneuvering Check

While still in open water and away from obstructions, perform some slow speed maneuvers as if approaching a dock or loading the boat on a trailer.  If there is a buoy nearby, that will give you a visual frame of reference (you don’t want to do this near a dock or pier for liability reasons). Take note of how responsive and tightly it turns and how it tracks at slow speeds.  Be aware that many single engine boats tend to “wander” a bit at idle speed.  Also, jet boats can be particularly challenging at first because you generally cannot steer them unless they are under power.  This isn’t necessarily a reason to avoid one but it is important to know there is a little bit of a “learning curve” going in.

Be sure to also maneuver the boat in reverse.  However, most single-engine boats do not steer well in that direction.  Pay attention to whether water comes in over the transom when doing this.  Again, certain types of boats with low gunnel heights are especially prone to taking on water but it also varies by boat brand, hull design and even the size/weight of the engine.

Equipment/Accessories Check

Finally, before the boat is put back on the trailer, be sure to take the time to try all of the accessories & electronic equipment that couldn’t be evaluated on land.  This includes things like the bilge pump, fish finders, livewells/aerators, trolling motor, etc.   Note that you might have to operate the boat at speed to check the fish finder to determine whether the transducer has been installed properly.

What if the Seller Doesn’t Offer a Sea Trial?

As mentioned earlier, many dealers and some private sellers are hesitant to offer Sea Trials.  This is perhaps why less than half of boaters in a 2021 industry study I conducted indicated that they did a Sea Trial before purchasing their most recent boat.

In some cases, their reasons are legitimate.   For example, dealers that are located inland and a considerable distance from water might be hesitant because of the time and expense involved.  Private sellers are naturally reluctant to do it if it is late in the season and the boat and engine is already winterized (and so they would have to re-winterize it if the sale does not go through).  Also, depending on the time of year and part of the country, a Sea Trial might not even be possible if area waterways are frozen over.

Despite their reasons, recognize that not doing a Sea Trial always means that you, the prospective buyer, are taking on additional risks.  Therefore, you should push to do one and possibly even walk away if the seller is not agreeable – unless you are willing to accept the added risk.  Some steps you could take (or the seller might offer) to make a Sea Trial acceptable to both the prospective buyer and seller are as follows:

  • Sign a purchase agreement and make a refundable deposit subject to a satisfactory Sea Trial.  This will tell the seller that you are serious and not just wasting their time.
  • Offer to pay for the Sea Trial.  The cost would be applied to the purchase price if you decide to purchase the boat.  This, of course, is not as attractive as the first option since you may be out some money if you pass on the boat but may be worth it depending on the perceived risk.

What should you do if the seller still refused to do a Sea Trial?  That depends on the situation and your risk tolerance.  For example, if it is a brand new boat being sold by a dealer, I would carefully research the reputation of that brand and even ask the dealer to contact prior customers of the same model.  If that checked out, then I would be inclined to go forward with the purchase.  Same if it was a newer model pre-owned boat that is still under factory warranty.

However, if it is an older model boat or one that has been used in saltwater and no longer under warranty, then I would be very hesitant to buy unless the price was low enough to be acceptable in a worst-case scenario (i.e., you could afford to do repairs and still come out Ok).

Should I Hire a Marine Surveyor?

A Marine Survey is like getting a home inspection.  It is a good way to find out about any issues before you make the purchase and can help with negotiations.  Though they are not cheap, a Marine Survey is critical if buying a fairly expensive boat or if you plan to finance a used boat because it might be required by the lending institution (since they will want some assurance regarding the investment too).

There are different types of surveys but, for used boat buyers, you will likely want is a “Condition and Valuation” (C&V) survey.  This entails a test of all systems and equipment and includes a Sea Trial. The purpose is to equip you (and possibly the lender) with the information needed to make an informed purchase decision.

A typical cost for a marine survey is around $25 to $35 per foot (approximately $500 to $1,000 for most boats).  However, prices will vary considerably based on the size/complexity of the boat and the location.  Assuming the cost is between $500 and $1,000, the question becomes whether it is worth this investment to potentially avoid a more expensive repair and the disappointment of getting something you are not happy with.  This, of course, is a personal decision that should be based, in part, on the perceived likelihood of a problem (based on the age and reputation of the boat and motor, and observations during your inspection and Sea Trial), the purchase price and your willingness to take risks.

To find an accredited marine surveyor, visit the National Association of Marine Surveyors (NAMS) or the Society of Accredited Marine Surveyors (SAMS).

Should I Get a Compression Check?

If you are shopping for a Used boat, many people will insist that you should get a compression check.  This is a diagnostic tool typically performed by a dealer or marine mechanic to determine the relative compression of each cylinder.  If the compression is low in one or more cylinders, this could indicate a problem with carbon build-up, piston rings sticking, faulty valves, a bad piston, a worn-out engine, etc.  Because these can be major issues, it may be worthwhile to have a compression check done and have the dealer/mechanic check the engine over at the same time.

However, if you did a Sea Trial and the engine was able to operate at the manufacturer’s maximum RPMs and the top speed was as anticipated, then there is less of an imperative to get the compression check.  That is because it is unlikely that the engine could perform at that level if there was a compression issue.

Also, if you choose to go with a compression check, it should be in addition to a Sea Trial, not a substitute for one.  Besides the fact that the test would not tell you anything about the boat’s ride/performance and operation of various accessories, the check is not performed under load and so it might not detect other mechanical issues with the engine.  The point being that a compression check could provide some valuable diagnostic information but is not sufficient by itself.

So, is it mandatory to get a compression check before buying a used boat?  Once again, it depends on the situation.  If it is an older boat/motor or you had some questions based on your Sea Trial, then absolutely you should take it to a marine dealer or mechanic to have things looked over.  However, you should call around ahead of time to see if you can find a dealer/mechanic willing to look over the boat in a timely manner and for a reasonable price.  On the other hand, if it is a relatively new boat and/or still under warranty and performed well during the Sea Trial, then you are likely fine to “roll the dice” and pass on the compression check/inspection.

Get a Printable Copy of the Checklists

To get a downloadable copy of the steps involved in doing a Sea Trial as described above plus other checklists for when shopping for a boat, click here: Used Boat Buyer Checklists.  This includes the following three items:

  • Used Boat Pre-Inspection Questions to ask the Seller
  • Bow-to-Stern Used Boat Evaluation Checklist
  • How to do a Sea Trial

These are in a print-friendly format and are handy to take along when shopping for your next boat.


Burnham, Nick.  “How to…Sea Trial a Boat.” YouTube Video.  Motor Boat & Yachting.  2016.

Burg, Randall.  “How to do a Sea Trial for a Power Boat.” YouTube Video.  Randall Burg Yacht and Ship.  2015.

Horsfall, Sean.  “Used Boat Buying Tips | The Value of a Compression Test.” Web Blog post.  Len’s Cove Marina.  13 November 2015.

Rudow, Lenny. “How to Compression Test an Outboard Motor | BoatUS.” YouTube Video.  BoatUS.  2019.

Checking Compression On An Outboard Engine.”  Web Blog post.  BoatUS.  April 2016.

Manning, Jeff.  “HOW TO DO A OUTBOARD COMPRESSION TEST.”, YouTube Video.  Team Reelin The Blues.  2019.

Boatman.  “How to Stop Your Boat From Pulling to The Right.“, Web Blog Post.  Boating for Beginners.  9 October 2018.

Types of Surveys.” Web Blog Post.  The American Boat & Yacht Council.

Uznali, Anri.  “How Much Does a Marine Survey Cost?” Web Blog Post.  San Diego Marine Surveyors.  23 July 2020.

Jerry Mona - BoaterInput

About the author

Jerry Mona is an avid boater and angler and long-time boating industry insider. With over three decades of experience, he is often considered to be the leading research expert with boaters and has helped numerous manufacturers and trade associations to understand the needs, wants, attitudes and behaviors of boaters. He now shares many of his insights about boats and boaters for free on his website.

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