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April 2, 2025

Off season maintenance

We write a lot of articles and technical pieces on electrical and electronic systems on board, but there’s much more to a boat than just the fancy gadgets and equipment on board. There’s a number of mechanical parts that need to be maintained, and the prime time to do this is the off season, when the boat is out of the water.

Of course, some boats don’t get taken out of the water for winter, so certain maintenance jobs like antifouling can’t be completed (which isn’t ideal, antifouling should be done once a year).

Engine / Drivetrain

One of the most common causes of damage during the winter months is water. Whether that’s water ingress getting into spark plugs due to poor seals, or cooling systems freezing, it can get quite costly, especially if the engine is damaged. Frozen water can crack blocks, heads, liners, and manifolds just to name a few.

The old advice used to be to drain the engine and drivetrain of all fluids over winter, and leave the engine sat dry over the winter months, however this idea has changed over time, and it’s now recommended that you do not drain everything as it can cause rust. Instead, anything which contains water needs to be flushed clean, and then filled back up with an anti-freeze mixture.

For fuel systems, it’s best to leave a small amount of fuel in the tank with necessary additives for both Petrol and Diesel engines. At the same time, it’s good practice to inspect the fuel injection system if you feel confident in doing so (if not, ask a marine engineer). Fuel lines can corrode and crack over time, filters need replacing and sometimes even the fuel filler cap can leak. Check for condensation or water ingress, as this is a sign of a filler cap which isn’t air tight, and this can lead to issues down the line (especially with Diesel engines).

Battery

Batteries are actually quite sensitive, and they can have a shortened life span in certain conditions or if they’re not charged and discharged correctly with cycles. When the boat isn’t being used, it’s tempting to leave it connected to a shore supply permanently, especially for those who run humidifiers etc, but this isn’t good for your battery.

For those who leave their boats in the water, galvanic corrosion can occur on board, affecting metallic equipment, especially those under the water line. If you want to leave it permanently connected to a shore supply, check that the supply has a galvanic isolator.

For a cheap solution that avoids the issues of galvanic corrosion, a small solar panel can be fitted to the battery, although again, it is better to disconnect batteries once they’re fully charged.

Boaters who live in areas where it can fall far below zero in the winter months, it is common practice to actually remove the battery off the boat and keep it stored in a warmer location at home.

Water Ingress

You’re out on the water in all sorts of weather conditions, so it’s pretty likely that you’re going to get water come on-board when out boating! This isn’t a problem so long as it’s cleaned regularly… however, when you park the boat up for winter months, you might not be around to clean it. Excess water build up will damage your interior, cause mold, mildew and damp to form, along with a lovely smell of stagnant water.

The most common reason for water gathering and potentially flooding a boat that’s docked up is blocked drains. Whilst it may seem a chore, it’s a simple task to check and remove any debris from drains to ensure any water is dealt with correctly.

If there is water on board when you come to dock the boat for winter, then a thorough clean before hand is always recommended. Drain and clean everything, and then ensure the boat has good ventilation. Leave vents, doors and lockers etc open to reduce the chance of damp returning.

One thing to note; if you are using a dehumidifier on board, then close all your vents etc… unless you are trying to dehumidify the earth! Else you’re running a piece of equipment that’s costing you money, for absolutely no benefit.