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Whether you own a 4ft tinny or a 60ft catamaran, carrying onboard spares is critical. You never know when you might need to dip into your spares kit to fix an issue, get out of trouble, or keep your trip going.
What you choose to stock depends largely on two things:
- Your boat’s engine and drive setup.
- What repairs you’re comfortable doing yourself.
Over the years, I’ve met plenty of boat owners who outsource all their maintenance to marine businesses. That’s fine if it works for you, but what happens if something goes wrong offshore, with no phone service and hours from the nearest service centre?
It does happen. I’ve seen people get stranded because of something simple, and one bad experience was enough for some people to lose confidence in boating altogether. But it doesn’t have to be that way.
If you’re reading this, I’m guessing you’re one of the many boaters who want to protect their investment by handling at least some of their own maintenance. Let’s break down the essential boat spares you should keep onboard, starting with the bare minimum and working into more specific parts.
General Spare Parts Every Boat Should Carry
1. Fluids
As an absolute minimum, stock fluids for every component with a dipstick or filler cap. This usually includes:
- Engine oil
- Gearbox oil
- Drive oil
- Power steering fluid
- Coolant
Check your owner’s manual (or component labels) for fluid types and volumes.
You don’t need to carry full system capacities onboard, just enough for top-ups.
For example, if your engine takes 40L of oil, it’s impractical to store that much onboard. Instead, keep 10-15L handy. Apply the same logic to other fluids based on your available space.
Some vessel owners who travel substantial distances and/or live aboard for long periods are the exception to the rule and may benefit from carrying a complete service kit for all mechanical equipment onboard.
2. Fuel Filters
Fuel contamination is one of the most common problems boaters face. Water can enter your fuel system from condensation, leaky filler caps, or even poor-quality marina fuel. A clogged filter can leave you dead in the water.
That’s why spare fuel filters are a must-have. Keep in mind:
- You’ll need the right tools (check out the captain’s tool tips below).
- Shut off fuel valves before removal.
- Diesel engines require fuel bleeding after filter changes—practice this before you need it in an emergency.
Not sure where to start with your diesel fuel system? Then check out my article – Complete Guide to Marine Diesel Fuel Systems: Bleeding, Leak Detection, and Maintenance.
Captain’s tool tip – need tools for fuel filter removal? Check out my picks for filter removal tools below.
3. Impellers
Your engine’s impeller is vital for cooling—it draws seawater in to prevent overheating. If it fails, overheating will shut you down fast.
- Carry a spare impeller and learn how to change it.
- Smaller impellers can be removed with screwdrivers, while larger diesel impellers often need special removal tools.
- Sand, blockages, or running dry can all shorten impeller life.
An impeller failure at sea can end your trip instantly, so this is one of the most valuable spares you can carry.
Want to know more about seawater pumps and impellers? This article has you covered – Mastering seawater pumps, how to inspect for damage and prevent failures.
Captain’s tool tip – Removing a seawater pump impeller can be tricky business without the right tooling. Check out my list of pullers below to find a puller to suit your needs.
Additional Handy Spares
If you have space, consider adding:
- Oil filters (engine, gearbox, power steering, etc.) – not essential, but useful.
- Extra belts and hoses – these wear items can break unexpectedly.
- Fuses – small, cheap, and easy to swap.
Think of it like the old food pyramid:
- Fluids = everyday essentials
- Fuel filters & impellers = regular essentials
- Oil filters = occasional extras
Parts Availability
Another point to consider is parts availability. The best thing about boating is the freedom and adventure of exploring remote or hard to get to places, and because of this, you may find some less-traveled places may not have a well-stocked mechanical shop nearby, so in these cases, it can be very advantageous to carry more spares.
Wrapping Up
Building your onboard spares kit isn’t about carrying every possible part; it’s about carrying what you’ll realistically use. Ask yourself:
- Am I confident doing this repair myself?
- Do I have the tools and know-how?
- Do I have space to store it on board?
By answering those questions, you’ll know what to include in your kit.
Keeping your vessel in top shape doesn’t have to be complicated. Explore The Everyday Captain for more practical guides, maintenance tips, and troubleshooting resources to help you save money, stay safe, and enjoy every trip on the water.
