Engine Recommendations with Pros and Cons: Engine Requirements § Maintenance, Reliability and Redundancy Considerations, Fuel Range and Consumption Optimization

Although every boat can satisfy the basic need of each boater, which is navigation in the water, there are tailored vessels for a specific purpose. The requirements of the boat are set by the waters it is used most often in, and by its purpose. A sailboat doing a transatlantic trip must be equipped with a small diesel motor, with orientation towards the economy, while the hull must be suitable for open waters. The vessel itself must have sufficient space for travel rations, like water and food, as well as an onboard kit with basic spare parts, safety equipment, and whatever else is necessary in such a demanding trip. And yes, it's demanding, and a lot of planning has to be done before setting sail - possible stops to refuel, before the open sea, or even some distraction for the killer whales that would try to snap off your rudder right after the Straits of Gibraltar. On the other hand, a 30 ft catamaran that is doing island hopping in the Aegean or the Adriatic Sea, will not need to plan such things in advance, besides providing a smooth and comfortable ride to the people onboard. Well, truth be told, even a raft could serve the purpose of island hopping, but you are not Tom Hanks filming Cast Away! 

How to Choose the Right Boat and Engine Combination

Choosing the right boat for each instance is not an easy task, since you simply cannot have it all. A petrol inboard cannot match the fuel efficiency of a diesel, yet its annual maintenance costs less. An outboard is always lighter than a stern-drive application, but its cost to acquire increases on higher horsepower and torque tiers. A catamaran is nice and stable, but it cannot get there as fast as a speedboat does. A 60 ft sailboat might be the ideal candidate for a transatlantic crossing, but navigating in shallow waters might be tricky due to its big rudder. Consequently, each hull and vessel type has its matching motor type.

Key Factors: Usage, Distance, Water Type, and Budget

So, you are browsing a boat-selling page, and you are about to set your first criteria that
would define your future vessel. Apparently, the first factor would be the amount you are willing to spend, but don’t forget to take into account the annual maintenance. You see, you may have found something that looks like a buying opportunity, say, for example, a 38ft Fairline Targa with a twin Volvo Penta D4-260, but if the engines are not in good condition, or even neglected, you will be surprised by the bill as soon as you open them to clean the intercoolers, or maintain the whole freshwater cooling system, also called closed cooling system. Speaking of which, a conventional seawater cooling system has a significant cheaper maintenance, at least in the short term.  PoseidonMarine carries an extensive range for cooling components for Volvo Penta, and even more parts for D4 & D6 engines, yet maintenance is a factor you should include within the purchase budget. The next thing you should consider is how you plan to use your boat. Do you want a small cruiser or speedboat just to have fun with your family or friends during your vacations? That would be maybe 50 working hours, plus another 50 throughout the year, whenever the chance is given. Are you ready to give up the comfort of your apartment, changing port every week? Is housing a nightmare in the Netherlands, and are you considering a boathouse? Well, a wise choice! Even if you consider all the above, you still need to define the waters you are navigating. A barge converted to a boathouse cannot sail in the Mediterranean, nor the Caribbean - she will always be limited within the river systems of central Europe. A catamaran will always be more versatile, switching easily between freshwater basins or the open Ocean. Doing so, you should always make sure your boat has the right anodes on it. Aluminum anodes for brackish and saltwater use, magnesium for freshwater, and zinc when the boat stays moored for long periods. 

Matching Hull Design with Engine Power

The hull design is a very critical element, since t affects the hydrodynamics of the boat. Stability, manoeuvrability, time needed to plane, or even limitation to plane – all these factors are highly affected by the combination of hull design and the engine combination. The engine selection, and generally the engine type, should always be in harmony with the hull and the intended use. It is usually the job of a hull engineer to determine the friction of the boat, the minimum power-to-weight ratio required to plane, and to simulate its speed on wide-open throttle (WOT) conditions, using various possible engine options. The engineer will choose among engines that have an optimal torque curve for the boat and meet the requirements of the rated horsepower. While doing the engine selection, its dimensions and weight must also be considered - not all engine rooms are the same. Besides all the aforementioned parameters, the transmission of this power into the water must be chosen wisely. Speaking of transmission, we should mention the factor “propeller”. If the motor struggles to hit its max RPM on wide-open throttle (WOT) conditions, it is very likely the installed propeller is too big in diameter, or it has a large pitch. This is called over-propping. Its opposite situation is under-propping: The propeller is too small, and the engine revs too easily, creating cavitation between the propeller and the cavitation plate. 

Fuel Efficiency vs Performance Trade-offs

Each boat has an optimal RPM range that becomes more fuel efficient, sacrificing speed to achieve higher fuel economy per mile. Even a small increase of a single knot is enough to raise your fuel expenses by 10%. That amount might be higher if the weather conditions are not assisting you. Planning a longer trip without the opportunity to refuel may require sacrificing some speed in order to increase your fuel autonomy. Your cruising range is also dependent on the reserve fuel your tank has (tank size). Since you know your tank’s capacity and your fuel burn rate, it is easy to calculate liters per nautical mile, or gallons per nautical mile - whatever measure you are used to.

Inboard vs Outboard vs Sterndrive Engines Explained

Inboard applications tend to have less maintenance, since there is no outdrive exposed to the elements. Additionally, the sternside is unobstructed, making it ideal for divers or just swimmers. Due to their design, inboard motors achieve a better weight distribution and a smoother ride, making them ideal for watersports. A significant disadvantage of an inboard application is the deeper draft it needs and the lack of tilting, especially in shallow waters. Smaller inboards sacrifice a lot of their hull’s space to accommodate the driving gear, leaving little space for the cabin or other utility space.

The sterndrive was an invention to create the golden ratio between the outboard and the inboard world. All the power of a big block motors, with the add-ons of trimming/tilting. Moving the transmission outside of the hull creates more space for the cabin, but there is a catch; sterndrives have higher maintenance costs and more frequent service intervals.

Lastly, the outboard motors maximize the deck space, since the whole power/drive unit is moved outside of the boat’s stern. The service of a small or medium-sized outboard is usually cheaper than any inboard or sterndrive, and they feature great capabilities and manoeuvrability in shallow waters. Adding a propeller guard makes them technically invulnerable against wood logs, stones, or other hazards. At the same time, it creates a safeguard for marine mammals and swimmers.

Best Boats for Fishing (Freshwater and Saltwater)

Each different style and hull type features different pros and cons when it comes to fishing in different environments. Therefore, it is necessary to consider the waters you are planning to use her. Deep sea fishing has totally different requirements compared to lake fishing. Even between different lakes the conditions may be different. Therefore, the first classification of boats will be for sea or freshwater. From there on, the classification concerns the type of fishing and the place in which it takes place.

Center Console Boats for Offshore Fishing

The offshore fishing takes place in waters deeper than 30 meters, and may exceed even thousands. The depth of the water is always dependent on the continental shelf, and the angle of it, but you are usually 20 to 30 miles away from the coast, when the sea turns from light blue to dark blue. When fishing in such an environment, especially for big-game like tuna, marlin, groupers, or other trophy fishes, it is very comfortable to have a 360° visibility. Imagine struggling with a mid-sized tuna, and you have to pass through a cabin - impossible. Additionally, the position of the central console in the middle of the boat offers a better spotting chance of schoolfish, or a bigger fish. Lastly, such boats are easier to clean, especially after a messing gutting of a large fish. Everything comes with a price though… Forget the comforts of a cabin, you will be exposed to the weather elements most of the time. There is also a space limitation you need to consider.

Bass Boats for Freshwater Lakes

Bass boats are the ideal solution for fishing in lakes and rivers. Their hulls are relatively flat, and their sides are low, thus, if the weather becomes stormy and windy, you should retreat to the shore. Their main advantage is that they are purpose-built for bass fishing. They are equipped with fishfinders, and their shallow draft offers amazing manoeuvrability in places other boats cannot reach. Since they are purpose-built, they may not be very comfortable for a different species fishing. Besides their instability in rough waters, one should consider that such boats can carry from 1-3 anglers, making them unsuitable for family occasions. 

Aluminum Fishing Boats for Rivers and Shallow Waters

Small aluminum boats are the ideal solution for the shallow waters of lakes and rivers. Their aluminum body is more resistant to impacts against rocks and stumps, and it will dent, while a fiberglass hull is at risk of cracking. Being lightweight, they achieve a higher draft, compared to a heavier plastic or fiberglass. Their maintenance is minimal, and can be combined with a small outboard motor. Don’t expect a high-quality ride, since their light weight can let stronger winds push them. Have in mind that their material is prone to galvanic corrosion, so if you plan to use them in brackish or seawater, make sure the right anodes are used.

Trawler Boats for Commercial and Long-Haul Fishing

Trawler boats and trawler yachts are vessels with open-sea capabilities, built to endure the rough conditions of the ocean, while offering large cargo space. Their bulky hull may compromise their cruising speed, but at the same time, this is what ensures their seaworthiness. Initially, these boats were available only as commercial fishers, but later the niche was evolved and trawler yachts became available to the wider public. Their main advantages are: 

1. Extended range, sometimes over 1000 miles on a single tank.

2. They are comfortable and practical at the same time.

3. Their low center of gravity make them really stable in rough waters.

Technically, they do not have a disadvantage, since they are built for a very specific purpose. One should consider that they cannot travel at the speed of a cruising yacht, but at the same time the cruiser cannot offer the stability and the range of a trawler yacht.

Recommended Engines for Fishing Boats

There is no such a thing as “the best engine for a fishing boat”, since there are two important variables that define your needs: your fishing style, and your location. The above two factors immediately affect the boat’s hull, which in turn define your motor’s requirements.

Fuel-Efficient Engines for Long Fishing Trips

A long-distance trip, whether is for fishing or just cruising, requires a good logistical management of fuel and supplies. If we add in the equation a remote location where refueling might not be possible, then our best choice would be any fuel-efficient motorthat can achieve low consumption rates, without sacrificing a lot of performance. Well, all this sounds like a Yanmar, right? These engines are renowned for their excellent fuel economy, due to their optimized fuel management system, which uses common-rail technology. Their small range of motors, like the GM, or the YM, achieve unbelievably low consumption numbers, and for that reason, they are very popular within the fishing world. Even their mid range, like the 3JH and 4JH series tend to be under 7 liters per hour at a cruising speed. If properly maintained, they are among the most reliable engines you can find.

Quiet Engines for Stealth Fishing Conditions

There are no 100% quiet internal combustion engines, but the most quiet are fuel-injected four-stroke outboards, operating at low RPMs. If your prey requires stealthy operations and incognito mode, then a brushless electrical motor would be your choice. It may not be enough to propel your boat, but will perform excellently as a trolling motor, without spooking the fish.

Best Horsepower Range by Boat Size

A general rule is to calculate one horsepower for every 25 lbs to 40 lbs of total weight. Here follows an example to understand it better: a 3000 lbs boat ÷40 lbs = Will require at least 75 HP to achieve a cruise speed. The same boat weight should be divided by 25 lbs, if that boat is used as a watersports. Additionally, you should always consider the shape of the hull. A flat hull will always plane easier, compared to a “deep-V” hull. 

Considering the above, every hull should be considered individually, based on your needs, its shape, and the overall load. However, we have created the following table, as a baseline.

Best Boats for Long Sea Voyages and Ocean Cruising

As mentioned before, there are purpose-built boats, engineered around a very specific task. When it comes to long sea voyages and ocean crossing, nothing can beat a Blue-Water Monohull Sailboat. They can handle almost any weather, and their fuel-free operation makes them an ideal choice for such a trip. According to our experience, some popular models are: Westsail 32, Hallberg-Rassy, and Contessa 32. For people who want a sturdy motor boat, an excellent choice would be a Nordhavn, or a Kadey-Krogen & Selene. If the idea is to travel a little bit faster, a cruising Catamaran, like an Outremer or Leopard & Fountaine Pajot, with a Yanmar rig, would be your best option. Volvo Penta D2-55/D2-60/D2-75 are also popular choices for such kinds of vessels, yet it is advised to keep an eye on their cooling/exhaust system for corrosion. Gladly, the introduction of stainless steel elbows and the knowledge shared from forum and Reddit users have significantly improved the situation. 

Engine Requirements for Long-Distance Cruising

The engine requirements of an ocean cruiser are defined by the reliability of the motor, the global spare parts availability and their supply network, high fuel efficiency, and their continuous duty ratings.

Reliability and Redundancy Considerations

A long-distance cruiser must be able to travel unobstructed by unexpected failures. Such was the story of the Caterpillar 3400-series and 3500-series, which became synonymous with bulletproof marine engines, built literally for harsh conditions and serious engine loading. Besides the financial impact of an unexpected repair, being in an isolated location may create even more difficulties in the event of an motor failure. Local availability of parts, capable technicians, and equipment are variables that you will have to consider in such an incident. 

Fuel Range and Consumption Optimization

Apart from the reliability of the motor, another equally important issue is the fuel range and the fuel economy. A gas-guzzling power plant will require larger tanks to achieve the same range, which would make the fuel economy even worse, considering the extra weight. The golden ratio between speed, motor longevity, and fuel economy is usually achieved around 60-75% of the max engine RPM. Always consider your hull type: A planing yacht will achieve higher speeds at the same RPMs, compared to a displacement motor yacht.

Engine Noise and Comfort Factors

Last but not least, an engine in a long-distance cruiser should be as quiet as possible, since you will spend a lot of time in it. Of course, if an engine is reliable, cheap to maintain, and has reasonable fuel consumption, you can consider ways to minimize its noise levels. Additional insulation in the engine compartment, better sealants on the hatch/engine room door, and modifications to the inlet filter, as well as the exhaust system, can significantly improve the noise levels.

Best Boats for Leisure and Recreational Use

There are many different vessel styles, built for a specific purpose when it comes to recreational use, therefore there is no “good” or “bad” boat type. More appropriately, your choice is either good, or bad, or maybe somewhere in the middle - balanced. Analyzing the term “leisure”, we understand that it's an activity we usually do in our free time, in order to enjoy ourselves, relax, and diversify our routine from chores and daily work. To sum it up, there is not an objective way of amusement. One may love slow cruises, while another may be a speed addict. Even when it comes to watersports, some prefer more adrenaline oriented like parasailing, while others enjoy the teamwork of a sailboat. There are also boaters whose main activity is fishing. Considering all the above, we understand that we are talking about many different navigational styles, need of comfort, engine requirements, or other factors that each different vessel type would ace in just a specific category, but you may make compromises if you put it in a different task. To say things a little differently, imagine an Azimouth confined in Ohrid lake, fishing trout. Or get your river-fishing aluminum boat and try using it for island hopping in Croatia.

Bowriders for Family Boating

The bowrider is a pleasure craft of small size, usually up to 10 meters and with a capacity of 8-10 people. As the name suggests, a bowrider has seats on the bow. This type of vessel is ideal for watersports, such as water skiing, tubing, and swimming. It can also be used for fishing, but a center-console boat has significant advantages. Bowriders lack cabins, toilets, and other comfort amenities; therefore, they are not designed for long trips. 

Pontoon Boats for Relaxation and Group Activities

Pontoon boats are very limited in their purpose, since they can be used in very calm waters, like lakes and slow-flowing rivers. Their major advantages are the large, flat area they have and the fact that they can accommodate a lot of people. Additionally, they have a very small draft, allowing navigation in shallow waters. There are larger pontoon boats in Central Europe that have been converted into pubs and bars, or even boathouses. Setting aside recreational use, pontoon boats are also used in transporting small vehicles on large lakes.

Cabin Cruisers for Weekend Trips

Cabin cruisers are vessels with at least one cabin berth, a kitchen, and a toilet. Their length varies between 7.5- 13.5 m, and anything above this range enters the class of yacht.

Deck Boats for Versatility

A deck boat is built with the purpose to have a larger deck area. Deck boats are all-rounders, combining speed, comfort, and transport capacity.  You can fish, you can do watersports, you can throw parties, or you can cruise relatively fast and comfortably. Of course, you cannot expect the performance of a speedboat, since the latter has a narrower bow to reduce drag, while the deck boat is wider, in order to accommodate more seats or open deck area. Of course, a deck boat shall have a V-hull, otherwise the boat starts crossing the borders of a pontoon. 

Engine Options for Recreational Boats with Pros and Cons

The first variable is the annual use someone plans to have a boat. Short- and long-term, low to medium hours per year tend to be less expensive with a petrol engine. Yes, a V8 or a guzzling two-stroke outboard may consume more per mile, but it is more expensive to change 40 liters of VDS4.5 oil on a twin installation of Volvo Penta D4-260, plus 10-plus liters of 75w90 gear oil, plus many filters, radiator cleaning, oil cooler cleaning, crankcase cleaning, engine anodes, exhaust pipe anodes, drive anodes….. Generally, we advise against recreational diesel engines unless you do more than 200 hours per year. Of course, every gain may come with a compromise: you cannot have the fuel autonomy of a D4-260 with a guzzler like a Yamaha 70BETO, but you will refuel more often. You will not have the silent operation of a large marine diesel, but that would be another compromise if your orientation is value for money.

Low Maintenance Engines for Casual Users

For a small to medium-sized boat with an open deck, or a central console, an outboard up the 100HP would be something it wouldn't cost a lot of money on an annual basis. Two-strokes tend to have cheaper maintenance, but you have to consider it may be already 30-plus-years old, with corrosion problems, worn cylinders, and near an expensive and inevitable repair. Statistically, the least expensive outboards in terms of spare parts are Yamaha, then Mercury and Suzuki. Johnson & Evinrude, although very reliable, they have higher maintenance costs. Tohatsu have constant supply problems and little parts are available aftermarket, while Honda may have ridiculously expensive parts and faster corrosion rate in exhaust pipes, head, and other components. An old, carburetted V6 mated to an Alpha One would be another rather affordable combination, but watch out of these manifolds, or you may be near a hydraulic situation before you know it.

All in all, smaller engines, smaller problems. The more complicated an engine becomes, the more components to maintain, which means higher expenses.

Best Engines with Pros and Cons

For small fishing boats, we would vote for any Yamaha outboard. The old two-strokes have the known problems on exhaust side covers and thermostat housings, clogged exhaust, but its easy to repair them, and have cheap parts. For larger boats, a Volvo Penta petrol would be a solid choice, but the newer generations have higher maintenance costs. A small sailboat will do great with an old Volvo Penta MD11/MD17, but always expect some difficulties with rare and NLA parts. A small Yanmar 3-cyl like the 3GM30 may be an easier to maintain option. Larger displacement engines have more advanced systems, diagnostics, silent operation, but all these come at a cost. 

Engine Priorities for Commercial Boats

The highest priority of a commercial boat’s engine is having as low operating costs as possible. To make this happen, the following statements must be true:

• A reliable engine without unpredictable breakdowns.

• Affordable and easy-to-source parts.

• Reasonable fuel consumption (fuel burn rate)

A commercial boat must work whenever needed. Being in the service when it's not expected to be for regular maintenance is a waste of money. Additionally, its maintenance parts should have a reasonable cost, without compromising their durability. At the same time, the parts must be easily accessible to order and deliverable on time.

Last but equally important, the specific fuel consumption must be as little as possible, without lacking the necessary horsepower or torque for the task. The less the liters per nautical mile needed, the more the profit from your boat exploitation increases.

Durability and Continuous Operation

The durability of a commercial marine engine, especially under conditions of constant load and continuous operation, is maybe the most important factor someone has to consider. Even if its consumables are kindly expensive, it cannot be compared to sudden damage, due to the following obvious reasons:

1. A damaged engine cannot produce work; therefore, its owner cannot exploit it during the time it is being repaired. Sometimes, cancellations due to a damaged engine can even have financial penalties when such contracts are signed. 

2. The repair period can be prolonged if the boat is located in some remote area like the Azores islands, due to delays in the required spare parts. Even the largest spare parts warehouses cannot stock “everything”.

3. If the damage takes place in a foreign port, the costs will be even higher.

Cost Efficiency and Service Intervals

Another serious factor someone has to consider is the cost of its regular maintenance, as well as the frequency of its intervals. The cost can be broken down in the following categories:

• Spare parts cost.

• Labour costs.

• Extra costs, like engine lifting.

The spare parts cost can be trimmed a little if you outsource the OEM parts, for some quality replacement ones, or negotiate better prices for a stock quantity of consumables. At the end of the day, a couple of anodes and filters do not have an expiration date. For impellers, try to keep them always “fresh”. The labour costs can also be reduced if you do not skip your regular maintenance schedule, since you will minimize the chance of an unpredicted engine failure, which will anyway cost more. So we come down to another important variable when choosing a commercial engine - its popularity. Which brand would have more aftermarket parts to choose from, or even less expensive genuine spares? An unpopular one like Steyr, or a global one like Volvo Penta or Yanmar? Of course the answer will be the last two. Last but not least, a commercial engine is built to last thousands of hours before a major overhaul. Until that expensive moment, it will burn fuel. Well, if it is a fuel-guzzler, that will not be a good choice.