Choosing the Right Outboard for Inflatable Boat

Choosing the Right Outboard for Inflatable Boat


Differences of the Outboard Motors

The main difference between motors today is the driving force. For PVC motorboats, you can choose both gasoline and electric motors. An inflatable boat does not need a motor with too much power. But since vehicles differ in their dimensions for control, they may need an engine with a capacity of 2 to 300 hp.

When choosing, many pay attention to fuel consumption. If we are talking about a gasoline engine, then, in this case, the majority prefer four-stroke engines since this saves up to 20% of fuel. But if we are talking about an inflatable boat, then do not forget that lighter units are preferable. Therefore, you should pay attention to a two-stroke.

And here - about the nuances that are important when choosing any motor.

What to Consider when Choosing the Boat Motor

 When choosing a motor for a boat - mainly an inflatable boat - they mean an outboard motor. In this case, the choice occurs between internal combustion engines (simply - gasoline) and electric battery motors. However, even motors of the same type have significant differences. An advantage is what someone considers a "minus" of the engine. Features of gasoline and electric motors are described separately. But here are some things to consider.

Power

When choosing a gasoline engine, specify which power is indicated as nominal. Most manufacturers suggest power at the propeller (propeller shaft) - the actual power output. But there are also motors, the "rating" of which is indicated by the power on the motor shaft. In this case, the output power will be lower than the declared one due to inevitable losses (for example, in the gearbox).

Also, with increasing speeds, friction and resistance to the driving force increase – and at some point, boat speed drops off. So when choosing a motor for an inflatable boat, consider this: A higher horsepower engine does not guarantee an increased rate.

Fuel Economy

When choosing, many pay attention to fuel consumption. If we are talking about a gasoline engine, then, in this case, the majority prefer four-stroke engines since this saves up to 20% of fuel. But if we are talking about an inflatable boat, then do not forget that lighter units are preferable. Therefore, you should pay attention to a two-stroke.

Right Outboard Motor Power

  • Minimum Power

The minimum required power is ¼ of the maximum allowable. This is the primary condition for choosing a motor for an inflatable boat. The minimum permissible power is sufficient for a fully loaded inflatable vessel to confidently get where it needs to, against the wind and current of a particular boat model.

  • Maximum Power

The maximum permissible motor power for an inflatable boat is calculated according to generally accepted methods. The primary indicator is the length of the inflatable vessel divided by the maximum width along the transom and for inflatables with a hinged transom - by the width of the stern. This "basic" full power is estimated considering the strength characteristics of the boat structure and, if necessary, is corrected (usually reduced).

This means that the inflatable boat has an excellent maximum power rating. It can maneuver with full loads at top speed. Aside from that, using a motor of this power does not threaten to destroy the boat; it maintains the needed level of safety for the crew and provides sufficient controllability of the vessel.

How to Calculate the Maximum Power

How much power is needed to fully load an inflatable boat on planning? It shouldn't be confused with the energy required to completely fill a planer, but many views "gliding" power as the max. One well-known formula for determining speedboat power is that the maximum load is divided by a number, depending on the boat's design. 

For boats designed as planning boats (typically with a flat bottom), the maximum load is divided by a number, depending on the boat's design. For planning boats (most often with a single fin), this would be 35, for displacement boats with a max deadweight of 20. Inflatable vessels generally have a standard hull, so the divider value falls between 27-30.

As you can see, neither the dimensions of the boat (which means its stability) nor the strength of the structure is taken into account. The power required for a fully loaded speedboat can sometimes be the same as the internationally rated maximum power. 

But, more often than not, the first is noticeably bigger and comes with the threat of wrecking the boat. The second is often enough for the inflatable boat to enter the glider even at over half capacity. So, a 600lb motorized inflatable boat allows for a 30hp outboard engine.

That's more than enough to carry this boat on its way to being a speedboat carrying a load of 600 pounds (five passengers, an engine, a 25-litre gas can, and 65 pounds of baggage).

Usually, in the technical characteristics of the boat, one power value is indicated - the maximum allowable. Moreover, responsible manufacturers suggest the correct full power (according to the international standard method). And in fact, it doesn't matter if this power is lower than that calculated for a fully loaded speedboat. Indeed, in reality, the planning mode is practically not used with such a load. 

Therefore, the proper maximum power rating is usually sufficient for the appropriate glider. And correct planning is when the hull is raised, and the boat goes almost parallel to the water's surface, touching its relatively small stern part of the bottom. A too steeply raised boat hull is, instead, improper handling.

However, it is widespread to give two ratings, called "maximum" and the other "recommended." As extensive testing and user experience show, "maximum" power can often be literally limited in this case. The boat will easily handle that engine power, and the structure collapses.

But what's being "recommended" turns out to be precisely that, the safest, permissible max.

In other words, if there's a mention of one motor power number, pay attention to it (don't go over it!). Use it to determine the minimum amount of power needed. If both "maximum" and "recommended" power numbers are listed, and you're not sure, the manufacturer has assigned the "maximum" power correctly, go with the "recommended" value.

One standard practical recommendation is to stock up on screws for different modes of inflatable boating: high-speed prop (with the most effective blade pitch; minimum load); cargo prop (most minor step; maximum load). Plus, actual horsepower (or, more accurately, thrust) also depends on how propellers are designed.

All-inclusive (with an intermediate step; for a typical load, which happens the most often).

Fixation 

The way that the engine is mounted plays a significant role. As a rule, the machine is fixed to the dance floor with a clamp for inflatable boats. But this approach has both advantages and disadvantages.

First of all, this is because the motor has a free-motion area. It could raise itself in a collision with an obstacle, lowering its weight. But when using vehicles with such a mounting system in big wave-filled reservoirs, it can be lost entirely.

Purposes

Many questions begin with these words, the answers to which are vital when choosing a motor for an inflatable boat. Where will your inflatable boat sail - on calm water or on waters with strong currents and waves? Is there a ban on certain types of engines in these bodies of water?

How often will you need to remove the motor? How do you plan on moving your inflatable boat and motor around? What are you most likely to use an inflatable boat for? If it's fishing – which type of fishing do you prefer?

They're typically laid-back family strolls or 'blown by the wind' rides, but on a speedboat when it comes to waterworks. Answering these questions will help you make an easier decision about what kind of boat will work best for you. 

So, say, if you're going to be using an inflatable boat primarily for fishing and definitely aren't planning on breaking any speed records, an electric motor might be the best choice. Especially when you consider these engines are lighter, more eco-friendly and far less expensive than gas-powered ones. When just the electric motor's power is enough from the point of view of the minimum needed power.

And if your inflatable boat requires even a minimum of relatively high power, or you want a motorized inflatable boat to please you with a reasonably high speed and planning - only gasoline engines provide suitable power so far.

On top of that, you should consider that certain waterways will ban gasoline-powered boats but allow their electric counterparts to whiz past unhindered. In those instances, electric outboards may be better suited to your needs than gas-powered ones.

Imagine that you plan to take a long voyage on the open seas at high speeds or want something with enough power for heavy loads (like multiple passengers). The best bet is to get one with a powerful gasoline engine in those cases. Also, gas engines perform better under stress than their smaller counterparts. 

Speaking of speed and power. It would seem that with an increase in revolutions (which means - and power consumption), the speed increases in direct proportion. This happens, for example, with a car moving on solid ground. But it doesn't work for a boat. 

Why? The vehicle moves on a consistently hard surface. And an inflatable boat creates an ever-larger wave with increasing speed, friction, and resistance to the driving force increases - and at some point, the boat's speed drops. Therefore, it is worth considering when choosing a motor for an inflatable boat: an engine with a higher power does not guarantee a gain in speed.

Is it two strokes or four-stroke engines?

These two strokes outboard motors use heavier fuels while giving similar horsepower. The tradition of two-stroke engines has been a long one. With a carburetor or electronic fuel injection providing fuel to the cylinder through an intake valve, during part of this feeding, the exhaust valve is also open, and up to 30% of the fuel escapes unburned, which leads to considerable fuel consumption. 

Its roar is louder and has a higher emissions capacity than any four-stroke motors. In determining these two choices, you will also need to be concerned about fuel economy as emissions cause many two-stroke engines to not meet standard emissions.

There are no additions of oils within a fuel, such as for two-stroke engines. It offers higher efficiency than the 2-stroke motor, which has a higher consumption of added oil in the fuel. Also, four-stroke engines deliver more power, making them better for bigger boats.

However, some newer outboards feature better systems like Direct Fuel Injection (DFI). These motors feature four-piston strokes per cycle and deliver excellent fuel efficiency regardless of whether there are four- or two-stroke engines or two.

Are two motors better than one?

Typically in fishing applications, there'd be two or three combinations. The boat is usually installed on the deck to be safe for the boater's vision if an engine goes down during sailing. This dual has made docking easier because the propeller motors rotate by rotating props. Rigging through two sets of motors requires repeatability in controls and complicated installation. Duals are also popular because they provide peace of mind that one engine will never let you down. Rather than taking advantage of an unusual situation or by introducing more efficient navigation in docks, an investor is paid more than he needs