How to buy an outboard engine for your boat

Outboard engines are continually advancing as new technology makes them more fuel-efficient and powerful. That translates to a much better experience on the water.

They can be expensive, costing anything from a few thousand dollars right up to more than $120,000.

But how do you find and buy a new outboard engine? Read on and find out.

The first place to start with any outboard engine upgrade is to look at your boat. Somewhere on it, in plain sight, will be what is called an Australian Builders Plate.

This plate is fitted to almost all new locally made and imported boats. It displays a raft of handy information, such as how much weight or people it can carry, how it will float if it sinks, and the one that’s relevant to us, the maximum-rated horsepower engine the boat can have fitted to it.

It’s time, then, to stop and think about how the engine you’ll be replacing has performed on the boat. If it was a bit thirsty, struggled to get an adult up on a ski or bogged down too much every time you had four people onboard, it is a sign you need to go a little bit higher with your new engine’s horsepower output.

Also think about how you expect to use the new engine, which is going to be more reliable and fuel-efficient than the one it replaces. If you’re going to start heading offshore and crossing bars to do it, a bit more performance will reap big benefits.

However, be very careful about how high you go. Sometimes a higher-performance engine can hurt the boat’s stability, so if you don’t want a boat to become a handful, be conservative.

Note, too, that some boat brands will offer the option of strengthened transoms that will allow a boat to take more horsepower. Just because you see a 250hp engine on the back of a similar boat to yours does not mean the maximum 200hp rating on the Australian Builders Plate can be ignored.

You’ll also need to look at your engine to determine what length of driveshaft you’ll need. Longer driveshafts, suited to boats with deeper transoms, can tend to cost more to buy than short-shaft ones, and fitting an engine with the wrong size gearcase to your boat will make it perform horribly so it is important to get it right.

There’s a lot to consider when buying a new outboard engine. Boats are very sensitive to how much weight is placed on the transom, so how much an engine weighs is likely to be the prime factor driving your buying decision.

This is also related to technology. A twin-camshaft engine that features separate intake and exhaust camshafts and four valves per cylinder has significantly more weight than a single-camshaft engine with the intake and exhaust cams all on one side pushing half the number of valves per cylinder.

Also counting is the number of cylinders. Yamaha’s three-cylinder 70hp outboard engine, for instance, weighs significantly less than its four-cylinder rivals. Likewise, Mercury’s 400hp V10 Verado outboard engine weighs less than V6 and V8 rivals.

Larger engines now come with digital shift and throttle controls, but traditional cable controls are available. Digital engine technology will open up a world of new features for skippers, but unless you plan to use it, the advances are a waste of money and the old analogue controls are a good choice.

What also varies widely between outboard engines is the amount of warranty they offer. There is usually a factory-backed component of two to three years, but if you have the engine serviced by an authorised dealer the warranty can extend by another two or three years.

There could also be extra expense involved in getting your outboard engine to talk to your boat’s multifunction chartplotter. Honda is the exception to this, with its engines talking the same electronic language as the rest of the boat.

Make up a side-by-side list of the strengths and weaknesses of all the engines you’re considering. The tests published on boatsales will almost always have real-world fuel figures to help you make comparisons.

You’ll then have to hunt around for a dealer that sells the brand of the outboard engine on which you settle. Note that this is also likely to be the dealer you will take the boat and outboard engine back to each time it is serviced, particularly under the extended warranty. It may be further to travel there than a closer dealer selling another engine brand.

As in the theatre, timing is everything when buying a new outboard engine. You’ll likely buy at the top of the market during the boating season, so it’s best to look for bargains around this.

One good time to buy is towards the end of the financial year. Outboard engines are a bit like cars, in that no one wants to carry last year’s stock. An end-of-financial-year run-out can result in some decent savings when factory bonuses are used to sweeten the deal 

There are also incentive programs throughout the year, usually involving a finance deal offered via the factory or even some straight dollars off an engine.

Note that unless the terms of the sale include the cost, you will need to pay for rigging – fitting the throttle and steering controls, mounting the engine, hooking it up to a digital gauge at the dash and so on. This can range up to several thousand, including the cost for the gauge fitted to the dash.

Note that if your old engine is still in good condition, you can probably sell it on consignment via the dealership that’s replacing it.

If you want to step up from an alloy prop to a stainless steel one, you may need to pay extra, too.

Have a look at the state of your transom. If the backing plate put between the hull and the engine mounts looks a bit careworn it’s an excellent time to replace it.

Unless it’s a portable outboard engine there’s no point in doing the hard work of removing the old engine yourself.

The dealer will have all the right gear. Make an appointment, drop off your boat, and in about a week’s time you’ll have a shiny, new engine mounted to it.

There will be a little bit of paperwork to fill out to officially add the new outboard engine to the boat, but once that is done, there’s nothing left but to enjoy it.

The dealership will explain to you the new outboard engine’s run-in method that will help you maximise its longevity.

Check for engine alarms, and look to see if features such as the trim gauge and speedo are working – if you don’t have an analogue dash, flick through all the multifunction touchscreen menus to see if the information is being pushed to the digital dashboard.

This usually involves limiting the number of revs for an extended period, and changing the oil at around 10 to 20 hours of runtime just in case there are any metal shavings floating around.

The run-in period will bed in the piston rings that slide up and down inside the cylinder, helping them seal, as well as lapping – the process where all the moving parts that touch each other settle in comfortably.

The run-in phase will usually include mixing up the revs below 4000rpm, never staying at the same revs for more than five minutes at a time. Get your dealer to write it all down for you.