Outboard Boat Motors

TIPS TO CHOOSING ENOUGH HORSEPOWER FOR YOUR BOAT

One of the first things anyone has to decide on when they are exploring purchasing a vessel is how much horsepower to go for. Getting the right level of horsepower is like walking a tightrope, opt for too little and you are restricted to a slow chug at 7 knots, too much and the cost of fuel and insurance skyrocket.

ERR ON THE LARGER SIDE

Bigger isn’t always better but I would recommend getting an engine with as much power as the boat can handle without becoming unsafe. It is easier to ease up on the throttle if it’s too much, than not be able to get up to the speed you need.

At the same time, before you load up your boat with an engine or outboard motor that will have you hurtling across the water at Mach1, you need to consider what your boat can handle. The more horsepower the engine has, the stronger the hull needs to be. This is because, at faster speeds, the hull hits the water harder and needs to be made of materials that can handle the force. Before you make any decisions on horsepower, consult the owner’s manual to find the minimum and maximum limits recommended by the manufacturer.

For example, my 17-foot vessel can handle between 50 and 90 horsepower. Anything less than 50 and the thing would barely move and anything more than 90 and the hull wouldn’t handle the impact. In this case, I wouldn’t go lower than 70 horsepower. A 50 horsepower motor might get the job done but the engine will have to work hard and this will mean it needs more fuel. A 70 or 90 horsepower motor will be much more efficient in the long-term (and more reliable).

INFLATABLES AND RIBS

Inflatables will need a motor with somewhere between 10 and 25 horsepower, depending on the length and weight of the vessel. RIBs are considerably heavier and will need at least 40 but in many cases would be better with somewhere between 50 and 70 horsepower. The difficulty with RIBs is that they are already carrying considerable weight and the outboard motor with 50hp, for example, is going to add a lot more. This is why many RIB owners like to use two-stroke engines. They are lighter than their four-stroke counterparts and you can stick a couple outboard motors on the back of your RIB to give it the power to carry several people and a lot of cargo.

ALUMINIUM VESSELS

Depending on your hull and manufacturers recommendations, aluminium vessels can take anything from a 50hp motor to a 300hp motor. At the top end, 250-300hp engines can carry four people at a cruising speed of 50mph. However, if you aren’t regularly carrying 3-4 people, you could probably manage with a 90hp engine that will comfortably carry two passengers at a cruising speed of 25mph. A 16-foot vessel could even manage on a 60hp motor without issue and with good fuel economy. The deciding factor when considering horsepower for aluminium vessels is how far do you usually travel in your boat. If it is only short distances, there isn’t much need for a 250hp motor.

BAY BOATS

Bay boats are made for saltwater fishing applications on still or protected water. Again, the size of the motor will depend largely on how far you intend to travel in the boat. Over short distances, a 100hp or 150hp motor should be fine. If you are heading further afield, a 250hp engine will be better suited. Bay boat enthusiasts will use either two-stroke or four-stroke motors depending on the personal preference. If they like to get up to plane speed quickly, a four-stroke will have more low-rpm torque.

TOWING SKIERS OR TUBES

Many boat owners assume that if they are regularly towing skiers or tubes, they need more horsepower. This isn’t always the case. Often they just need more low-rpm torque. For this purpose, a four-stroke engine should do the job, even if it doesn’t have 250 or 300hp.

When considering horsepower, always read the manufacturers recommendations and choose something in the upper end of that spectrum to get the best fuel economy and reliability. It is worth considering what you need your boat for when choosing how much horsepower to go for and whether or not to go for a two-stroke or four-stroke engine.


 

Do you have anything to add? Do you have any suggestions on horsepower? Let us know in the comments section below.

 

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Martin White
martinw@dinga.com.au

Martin is huge on everything outdoors and is even bigger on driving and technology. He loves boats, new stuff and writing about it.