Whether you’re hauling out the boat for the winter or for an annual bottom paint job, it pays to ask and answer a number of questions before she comes out of the water. A formal sea trial prior to hauling will do just that and can be combined with your trip to the yard.

Depending on the boat and your budget, you might want to bring a mechanic along, but the following procedures are within reach of most boat owners. In any case, you will need at least two people: one to operate the boat and the other to perform the inspections.

Click here for a printable PDF of the Trial Run Checklist.

Getting Started

Begin by placing clean white absorbent pads under the engines. They will remain there until the end of the sea trial. Put them down and forget about them for now.

Inspect all hoses for signs of chafe or cracking. Squeeze each hose if possible; any crunchiness points to a failing hose. While the engine is cold, spend some time laying eyes and hands on the various components, looking for leaks or signs of wear or loose connections.

Turn the key switch to the “on” position. The engine alarms should sound. If you don’t hear an alarm, then the alarms are not working and need to be repaired.

Before starting the engine, disconnect the shore-power cord. A battery charger can provide cover for a failing battery, so disconnecting shore power with the generator off will help to expose a weak battery. The engine should start within a few seconds.

As soon as the engine starts, look over the transom and note any smoke—in both quantity and color. If you have twin engines, start one, observe and then shut it down and start the other. If the second one starts while the first one runs, it will be harder to detect any issues related to smoke or starting.

The next check takes a little courage.

Each shaft has a water-injection hose at the shaft seal. Some seawater from the engine-cooling loop exits through a hose into the seal. With the engine running at idle, remove the hose from the seal and make sure you have a healthy stream of water pumping out.

While the hose is removed from the shaft seal, water will stream into the bilge, but the quantity and duration will be manageable. If the nipple looks corroded, it should be replaced when the boat is hauled.

Underway

Start by running the boat in forward at idle rpm. If you hear a rattle that only occurs in this situation, you might have a failing damper plate in your transmission. The damper plate helps to absorb the shock loads imparted by the engine to the transmission.

Before the engine compartment gets too hot, check the engine mounts for excessive travel. While one person operates the boat, you will need to be where you can have a close look at each engine mount. Run the boat in forward at 1000 rpm for a minute, and then shift into neutral for three to five seconds. Then, shift into reverse, followed immediately by increasing rpm to about 50 percent of maximum for a few seconds. Watch an engine mount during this process, and look for any movement of the mount on the engine beds, or for any flex in the mount that’s more than barely noticeable.

If you want to get a professional opinion later, take a video. Repeat this test as often as needed to observe each mount individually (for a twin-screw boat, that means eight mounts).

Once the engine has warmed up, run the boat to your normal cruising rpm. Record the following data: rpm, speed, coolant temperature, oil pressure and battery voltage. Note any smoke or vibration.

An infrared pyrometer, or “temp gun,” will be needed for the next steps. Find the heat exchanger for the engine coolant. There will be seawater going in and coming out, and coolant going in and coming out. Trace the hoses so that you can identify the flow direction, and then shoot the temperature of the coolant hose going into the exchanger. Then, shoot the temperature of the coolant hose exiting. Record the temperatures. There should be at least a 10-degree differential. (See “Troubleshooter” January/February 2015 for a full description of temperature checks.)

While at cruise speed, have a look at the shaft seal. If you have a conventional stuffing box, check the bronze housing with your temp gun. The seal should be no more than 20 degrees Fahrenheit above the ambient seawater temperature, and no more than 130 degrees overall.

Observe the drip rate: A drip per second at cruise would be acceptable, but if drips stream out, it means the gland needs service. For dripless seals, simply check for leaks. These seals should remain dripless.

Stress Test

After 10 minutes or more at cruise, push the engine up to 90 percent of the maximum rated rpm. If your engine has a 3000 rpm rating, run it at 2700. Repeat all of the checks listed earlier, and record the results. Pay close attention to the coolant temperature. It might rise slightly from the cruise speed test, but it should level off.

Unless you have an engine that is 20 years old or older—and that you never run at wide open throttle—go ahead and push the throttle to the maximum. Every engine is rated to run safely at wide open for a percentage of total run time. Watch the temperature closely. If it climbs without leveling off, then you will need to back off. If that happens, your cooling system needs service or modification. You should be able to run at wide open without the system overheating.

Note the maximum rpm achieved, and then run for about five minutes. Record the same information as before. If you are not able to achieve the rated maximum rpm, there might be a fouled bottom or prop. You can diagnose restricted air supply with this simple test: Open an exterior door, and then lift a hatch or door to the engine room. If the rpm increases, the air flow is inadequate.

After five minutes, reduce the rpm and head back to the dock.

Back at the Dock

Now would be a great time to take oil and coolant samples. This process must be done in a prescribed manner, and in most cases, a mechanic should do it. If you are conducting the sea trial prior to taking your boat to the yard for the winter, ask to have someone available when you arrive. If that is not possible, then samples can be drawn at the time of winterizing the engines.

Once the engine room cools down, crawl around the engines with a flashlight and mirror. Look over, under and around all components for signs of leaks. Check the white absorbent pads for any stains.

You now have a valuable set of data points and observations to create your annual haul-out work list. Formalizing the process ensures that you will cover the necessary checkpoints. This information will help you get the most out of your haul out, and for those hauling for the winter, you will have reduced the likelihood of recommissioning delays in the spring or before your next cruise. 

Click here for a printable PDF of the Trial Run Checklist.