CAN I ADD MORE HORSEPOWER TO MY MOTOR YACHT?
THE ANSWER IS…
Captain Vadimo | 27th of March 2022
Before answering the above question, let’s understand where such a question is coming from.
In the past 15 years, I have received an enormous number of similar questions from almost every second client (if not from every single one) who was planning to purchase a brand new, used, or even build a bespoke boat. And that was regardless of the type, size, and price of the boat they were planning to purchase.
The below article is intended to explain the topic and answer the question in the most simplest way.
The answer you’d like is “YES”. The right answer is a counter-question
What do you want? This is the most important question that inexperienced and experienced boat users must ask themselves. What do I want as a boat user?
We must be clear with our requirements, be in harmony with our wishes, and do remember that each and every boat design has solid science behind it. So, first of all, you have to decide what are you looking for.
Below we will discuss three different motorboat types that are most popular among the majority of boating enthusiasts.
The first type is a nice spacious motor yacht with a few cabins that have almost everything for accommodating your family and/or friends for a weekend, or, maybe even for a week. Such a vessel would have a large galley, a day head (maybe even a few), lounge/dining/chillout areas in-/and outside, a wine cellar, a dishwasher, a large fridge with freezer, a washing machine, a dryer, etc. You can continue the list. But please, do not forget to note the weight and dimensions next to each of those “comfort-focused features” that come to your mind. We will use these notes later.
The second type of a boat you may be interested in is a small-to-medium size motor yacht (40-60ft / 12-18m) for short trips that do not require onboard accommodations for a bunch of friends. The purpose of such a boat is having more fun yet experiencing a decent level of comfort. Worth mentioning, when we say “fun” we also mean “speed”.
In many cases, this would be the type that some world-famous boat and yacht designers like to work with. Simply because it creates more flexibility for self-expression for a designer - a chance to make an eye-catching exterior design while having a number of good opportunities in creating functional bespoke interiors. So, I would call this type of ownership “mild egocentric boating“.
The third type is a high-speed craft that flies above the water, has thousands of horsepower under the hood, burns thousands of gallons of fuel, and makes you feel like being on top of the world. It may also accommodate a small fridge for a dozen of beers just to bring that “top of the world” even higher. This boat will have a minimum number of comfort features, however, this does not in any way diminish its beauty. In most cases, high-speed boats are beautiful beasts with lots of science backing their performance.
The below picture graphically represents those three types of boats I’ve mentioned previously.
Explaining 3 major motorboat types
We must remember that our world is large and diverse. Therefore, preferences of different families across the globe may also vary.
Here we can see that the Type 1 boat is far away from having a “cigarette type” hull shape. Because it is designed to accommodate your long list (including a few positions requested by your loved ones) of comfort-focused features, which have their own sizes and weights that you’ve noted already. All these, somehow, must be “stuffed” into the hull. Once done, there is very little room left for science (Naval Architecture) that is in charge of balancing between your wishes, weight & center of gravity (COG), shape of the hull, and rationalism. Especially, when it comes to the capacity of engines.
Someone said “science”
Yes, I did.
Remember, a Naval Architect is your “best friend” when it comes to understanding your needs and what industry can deliver. Naval Architects are your key tool in achieving goals. However, keep in mind - they are not magicians. There are rules.
In the boatbuilding industry, it all depends on what the client needs - whether a comfortable, efficient, large, and heavy “family yacht”, a “cigarette-style” powerboat that burns thousands of gallons of fuel just to keep the owner satisfied with the moment or something in between, as a balanced and, yet, sufficient compromise.
There is a very fragile balance between hull shape, weight, the center of gravity, deadrise, aspect ratio (length versus beam), and power. All the above elements must be put together with the right values to make a decent yacht. This takes an enormous effort in analyzing hundreds of different criteria and parameters on the path to achieving the design that will fit for purpose.
For example, the below picture (Fig.2) represents two cross-sections of the monohull planing hulls with the most common angles of the deadrise.
Explaining the deadrise
As you can see, there are two groups of deadrise angles: between 16 and 19 degrees and between 20 and 24 degrees. Many industry professionals call both groups a “deep V-hull”. I would rather call the first group a “deep V-hull” (Sec 1) and the second a “shallow V-hull” (Sec 2).
What’s the difference?
If you are looking into a family yacht, a Naval Architect who designed it most probably has chosen a “deep V-hull”. Simply because such a hull “seats” deeper in the water (more displacement, more weight, more stuff), is more stable, has a lower center of gravity, and is perfect for handling rough seas, somewhere in the Mediterranean. Such a hull will have a higher resistance due to its geometry and lower value of the lifting forces that will push your boat up and keep it surfing/gliding at speed. This means it would require a lot of power to go into and stay in the planning mode. Therefore, such a vessel will have an “optimal” propulsion package that won’t drain your bank account and will allow you to safely transit from one place to another while enjoying perfect relaxing moments with your loved ones.
In its turn, a “shallow V-hull” will be perfect for cruising in calm and shallow seas, somewhere, for instance, near Everglades National Park in Florida. Such a hull when well balanced and sized is easier to push into planning mode. It requires relatively less effort to achieve higher speed if the length to beam ratio is correct, the center of gravity is optimal, and the total weight is kept to the absolute minimum. Cool, isn’t it? Now something to note.
For such a boat, adding a dishwasher, washing machine with dryer, stove, and marble countertops will literally mean another 1000kg (2200lbs) of extra weight and a death sentence to efficiency. All left to decide whether it's gonna be by firing squad, drowning, or hanging.
Looking back at the three types of boats that we discussed, I would roughly sort them as follows. Type 1 and Type 2 would most probably use a “deep V-hull” while Type 3 will be using a “shallow V-hull”.
Is Type 2 the best choice?
Well, Type 2 is rather a compromise between comfort and speed. It includes features from each of the other boat types, but it is yet compromised. You won’t be able to cruise at 100 knots and yet won’t be able to accommodate "a wagon and a small trolley” of guests.
It is rather perfect for a small family with a couple of kids or a short-term charter (if chartered).
Is stepped hull a dream-saver?
No, it’s not.
Stepped hull and other innovative high-tech add-ons (Petestep®, for instance) to the bottom of your boat are great and they might improve the overall characteristics, but only to a certain extent. Let’s put it this way. Your boat can live a long and prosperous life without them. I call these features “nice-to-have” (“N-H-T” Features). It is very cool to have them, but they are not key critical for your survival at sea when it comes to Beaufort scale 12 storms.
Such high-tech add-ons could improve your speed by a few knots, reduce hull resistance and slightly raise the level of comfort while navigating through seas. Although, it’s important to remember that such features will work only with certain types of boats. To put it crudely, there is a better chance to succeed if such add-ons are used on a Type 3 boat.
Talking about other “nice-to-have” features. Those are also related to anti-roll systems (gyro stabilizer), fishing gear (outriggers, downriggers, rod holders, live bait, etc.), foldable gunwales, lifting platforms, watersport toys, and many-many others. All these also have their size and weight despite their pleasurable purposes.
Understood. I have all the money on earth. Can I have more horsepower?
It’s not about the money. It is all about common sense. There is absolutely no reason to waste money on something that will never work just because it was never meant to.
But you can have a well-balanced product right in your hands (or under your feet) if common sense is a part of your mindset (if not – start practicing it). Have a look at the below chart that graphically represents those three major groups of requirements that most boat owners are focused on.
Principle of “O” Formula
The graph speaks for itself except for the center part called the “O” Formula. So, what’s that?
Here I call the principle of the well-balanced boat design an “Optimum” Formula. The success of this principle is achievable if the boat owners will take their expectations on comfort, additional nice-to-have features, and on speed/power and divide them by 2. In this case, our “Optimum” Formula will come to the following view:
(Comfort-Size / 2) + (N-T-H Features / 2) + (Power-Speed / 2) = Optimum
It is important to remember that all the above is valid if you are buying/building a small planing craft (6-24m / 20-79ft) and not a Superyacht.
So, can you put more powerful engines into your all-inclusive motor yacht? The answer is yes, but it would be as insane as attaching the rocket engine to an elephant.
In other words, there is absolutely no point in increasing the capacity of your engines if your boat is not designed for speed. By doubling the engine power you will never double the speed. Instead, you will triple the expenses on fuel and multiplicate the negative impact on the environment.
I would like to finish this article with the following comparison. The boating industry is pretty much similar to the car industry. When we chose cars, we all know that the market will deliver us a spacious minivan when we are a family with kids, it will deliver a good-looking sedan when we care about appearance/design and features, and we chose a sportcar or limousine manufactured by the brand known across the world when we really care about the prestige.
There is no point in putting 4x4 off-road drive into the average family minivan which is used over the weekend for getting supplies from the supermarket. It would be absurd.
Once you are in harmony with your expectations and understand the possibilities of the boating market, you will be always capable of getting a well-balanced boat that satisfies most of your requirements. Just stay aware and with a good bunch of common sense.