Top tips for buying a second hand outboard engine
There are many ways to avoid buying an outboard engine that doesn’t work, or that might cause you problems in the future. You don’t need a wealth of mechanical experience to check key elements of the outboard engine you’re interested in. Hopefully this advice will help you find a reliable outboard that suits your needs exactly!
What to look for
It’s important to first check the weight and horsepower rating for your boat. Remember that if you overpower a boat you could well experience bad handling, and this could make insurance claims problematic. A worst case scenario is that you can sink a displacement hulled open boat with too much throttle.
If you’re aiming to use the outboard engine at sea, you probably want at least 2/3 of the max HP rating. It's pointless under-powering a planing hull as the engine will be straining to get it to plane, and when planing will use more fuel for a given speed than a bigger engine with less throttle opening.
There are generally three shaft lengths: Short (17-18"), Long (20-21") and Extra-long (25") and these coincide with the height of your boat's transom.
The shaft length should be measured from the anti ventilation plate above the propeller, to the part of the clamp that sits on the transom. Don’t measure from the top of the clamp to the centre of the propeller as it has nothing to do with how tall the engine is.
Ask about fuel consumption and think carefully about whether or not this will be affordable for you in the long term. Fuel consumption should not exceed 10% of the horsepower of the motor in gallons per hour. So a 50HP will use around 5 gallons per hour at Wide Open Throttle. Modern outboards use less but still use this as a rule of thumb and you'll never run out of fuel.
When looking at a second hand outboard engine, ask to see the engine running and make sure that the cooling system is working properly. If there’s no problem with the cooling system you’ll see a tell tale stream of water coming from the engine. If there’s no proper cooling you’re probably looking at an overheated, worthless and damaged motor.
If there is a problem with compression it can cost upwards of £500 to repair – and unfortunately this is a very common issue with outboard engines, particulalry those over 10 years old. This is worth testing if you can, either by taking a mechanic with you or doing your own test.
To test for low or uneven compression simply take with you a compression tester, which costs about £10 to £20, and a socket set for taking out spark plugs, making sure you know what the compression reading should be for this model.
Remove the petrol hose going from the fuel tank to the outside of the engine. Take off a lead going to a spark plug and using the socket set simply unscrew the spark plug. Screw in the compression tester and turn over the engine for a few seconds.
Make a noteof the reading and then replace the spark plug and the lead and repeat for the other cylinders. If you’re looking at a small engine it might have its own fuel tank that can be drained instead of disconnecting the fuel hose. Remember you must never start on outboard out of the water without a water supply, as this can cause serious damage!
What should you look out for? If you discover the reading is low or there is more than 10% difference between each cylinder you are looking at a costly problem – so it’s probably best to avoid.
If possible it is also good practice to see the engine running under stress i.e. pushing a boat, but this is not always possible. So a compression test is the next best thing.
Other areas to consider
- What condition is the gearbox in?
- Has the power head been well maintained with gaskets in working order and metal plates bolted with airtight seals?
- With 4 stoke engines check the oil filter - often it will have the date it was replaced on it. You can tell a lot by the colour of the oil.
If the seller claims the engine has been recently serviced or he/she is boasting low hours usage, ask for the relevant paperwork and service bills that will prove this.
Be wary if they can’t produce the right paperwork. If you are buying through a dealer you may well be offered a 3-6 month warranty, which is well worth having.
Finally don’t forget to ask if the outboard engine comes with any extras – rev counter, wiring loom, throttle and steering, spare impeller, engine oil. These will all save you money if included in the sale.
Boatshop24 has a wide range of outboard motors for sale. Click here to browse the range!
Photo: Thanks to Morgan Marine (Top) Hidea 15HP 4 Stroke outboard engine (bottom)