There’s a reason racehorses train. It helps them build sufficient muscle and stamina to power their bodies around the tracks and over jumps.
In a sense, boats are no different. Their food is fuel but their power comes from the engines that shift them through the water at often remarkable speeds.
So, how do you go about selecting the right amount of horsepower to re-power your boat engine or when you want to upgrade your boat? Read on to find out.
Horsepower is a unit used to measure power typically of engines. The Scottish engineer, James Watt, coined the phrase when comparing the output of his steam engines with the power of horses used to pull loads.
Power makes acceleration happen. More power tends to mean faster acceleration. There’s a slight complication because horsepower or mechanical horsepower to be precise was an imperial measurement. Because Australia uses the metric system, 1 unit of metric horsepower is equal to 735,5 watts.
The torque, weight, aerodynamics and frictional losses are some of the dependencies when deciding on the right hp for your boat’s engine. However, there is a more critical factor: the legal maximum as stated by the manufacturer.
Horsepower vs Torque
Torque is the rotating effort or twisting of any shaft. The drive shaft driven by an outboard motor is a classic example. It’s quite easy to get torque and hp confused. Here’s an analogy:
Picture 2 people shovelling 2 equal piles of sand. Both shift the load at the same time. The first person uses a small shovel but works incredibly fast. The other person has a big shovel that carries more load so completes the job with fewer movements. The first person is equivalent to horsepower and the second to torque.
It’s horses for courses but you need to consider both hp and torque for the best acceleration and ideal power when you want to re-power your boat engine.
The Weight of the Boat
You should check the details on the Australian builder’s plate (ABP) or the manufacturer’s compliance plate, to decide on the maximum number of adults a boat can legally carry. Understanding your boat’s maximum load is probably the biggest consideration when weighing up engine size when you want to re-power your boat.
You may believe that you’ll never carry the maximum load and therefore don’t need the maximum permitted engine size. That can be a mistake. Many marine experts would recommend going for the maximum hp or engine size that your boat manufacturer specifies.
It can save you money further down the line, especially should you ever come to resell your boat with its engine.
The Use of the Boat
You might think that a smaller engine is always going to use less fuel. That’s not always going to be the case. If the engine is straining under a heavy load, it’s likely to use more fuel than a bigger engine that can handle the larger load.
Bigger engines with greater horsepower offer numerous benefits for greater comfort. These include:
- Higher speeds: useful if you’re fishing and moving from location to location
- Better handling, especially at midrange speeds
- Handling waterports such as waterskiing
- Easier manoeuvrability
- Better control and more security in harsher weather conditions
The bottom line is this. Your engine wishlist should match your personal preferences and these will typically depend on how you primarily intend to use your boat.
Acceleration, top speeds and reliability should all play into your choice. So should the potential for lightweight design and better fuel efficiency so that you have everything you need to push your boat to the max. You may plan just cruising slowly around one weekend but want more power on other occasions when entertaining the family on board.
2-Stroke vs 4-Stroke Engines
Both 2 and 4-stroke outboard motors have their own technical strengths and weaknesses.
A benefit of a 2-stroke engine has been that it has tended to weigh less when compared to a 4-stroke outboard motor. That is because it has fewer moving parts. A downside of a 2-stroke engine has historically been an increase in pollution and often less efficient fuel consumption.
An advantage of 2-stroke engines is that they tend to need less maintenance because there are fewer moving parts.
A 4-stroke engine may make more sense if you’re using your boat mainly for fishing trips. A cleaner environment ultimately translates into better fishing opportunities. If you need to go greater distances, the 4-stroke is a good choice because it will tend to give better fuel economy.
If lifting a heavy boat engine out of the water is not going to suit you, then a 2-stroke may be a better choice. It’s also possible to find 2-stroke boat motors with superb emission standards. And, manufacturers like Mercury have a range of 4-stroke engines that are more lightweight.
Modern and Innovative
If you intend to re-power your boat engine or upgrade your boat, you should bear in mind that outboards have come a long way over the past few years.
Mercury has invested heavily in technological development. The result is a range of engines that are second to none. The emphasis has been on quality, performance, innovation and reliability. That’s why Mercury is the only brand we stock.
We are able to offer a range of Mercury outboards to suit all needs. These include:
- Hardworking commercial engines if you plan to make your living on the water
- Professional standard performance engines for competitive fishermen
- Engines like SportJet that offer maximum manoeuvrability in shallow waters
- Quiet, efficient and lightweight engines for everyday use
Often it’s the small nuances that can make all the difference. We are always happy to talk through the finer points that matter most to you.
Come and See Us for Your Boat Engine Needs
Whether you plan to re-power your boat engine, upgrade your boat or are looking for Brisbane boat servicing, Mike’s Marine has you covered. You can find us in Brisbane’s Bayside at Capalaba.
Get in touch with us at Mike’s Marine today. There’s nothing we enjoy more than talking about boats and engine sizes. Feel free to drop by for a chat!