Selecting the Right Outboard Engine - 04/19/2017

The engine is the most important and most costly component on or in your boat. To a large extent, as goes the engine, so goes the boating experience. Making a mistake when choosing an engine — either under powering or over powering — can be costly.

Selecting the Right Outboard Engine
Do you want to go 75 mph or 7 knots? The speed of your boat is one of its most important attributes.

Speed and the Boat’s Hull

The desired speed will be an important factor in engine selection. Those wishing to travel at high speeds will find the purchase price of an engine and boat equally high. The higher the horsepower rating the stronger the hull has to be. The faster your boat hits the water, the harder the hit is. Think of a car running over a series of speed bumps placed every 30' across the road. Imagine what would happen to that car if it traveled over a mile or two of those bumps at 70 mph.

The more high-technology materials such as Kevlar and carbon-fiber that are used in the hull, and the more stringers and bulkheads that need to be put into the boat, to say nothing of a thicker, cored laminate, the more the hull will cost. Those who ever wondered why high-performance boats are so expensive with so little inside them now know the answer.

With these things in mind, let’s now look at eight major types of small boats and see what engines might be best for your application.

Advances in Outboards

Technological advancements in the design and construction of outboard motors has pretty much done away with the idea of four-stroke outboards being noticeably heavier than two-stroke models of the same horsepower output. Looking at 200-hp engines, Mercury’s four-stroke Verado 200 is a four-cylinder model with a supercharger that has a displacement of 1.7 liters. The lightest version of this model is listed at 510 pounds (231 kg).

The two-stroke Mercury Optimax 200 and 200 Pro XS are direct-injected 3.0-liter V-6s with the lightest weight listed at 505 pounds (229 kg). Comparatively, the Evinrude E-TEC G2 200 is a two-stroke direct-injected V-6 with a 2.7-liter displacement that tips the scales at 528 pounds (239 kg) for the lightest model. Yamaha’s F200 is a 2.8-liter in-line four cylinder four-stroke that weighs 487 pounds (221 kg). The four-stroke is the lightest of the bunch. Clearly weight is no longer just a matter of the combustion process.

Two-stroke outboards are no longer the smoky, hard-to-start engines of the past. Nor do they guzzle fuel these days. Virtually all two stroke engines are far more fuel efficient than they were just 5 years ago. In particularly, the Evinrude E-TEC G2 series is remarkably fuel efficient and can got toe-to-toe with the best 4-stroke in class on fuel efficiency.

Selecting the Right Outboard Engine
The Mercury 200 Verado is a supercharged four-stroke which gives this engine low-end torque competitive with 4-stroke engines.

Selecting the Right Outboard Engine
The 200 Optimax is a popular 2-stroke outboard that is only five pounds (2.27 kg) lighter than the Verado.

Selecting the Right Outboard Engine
The E-TEC G2 200 is slightly heavier than the other engines in class because it has internal steering and an integral oil tank that the other engines do not have, and so their external equipment is not counted in their weight. It is also competitive with 4-stroke engines in fuel efficiency.

Selecting the Right Outboard Engine
Yamaha focused on making its 4-stroke 200-hp among the lightest outboards in its power range.

1. RIBs and Inflatables

Inflatables and Rigid Hull Inflatables (RIBs) are not as easy to power as one might think. The days of the little kickers are over except for the compact inflatables that one can roll up and store in a boat’s lazarette or the trunk of a car. Often, the weight of the engine and how much the owner can lug will be the determining factor on max horsepower, usually 9.9 to 25-hp for small inflatables.

RIBs take more horsepower because they are far heavier than inflatable boats. All boats are weight sensitive and RIBs are no exception. For that reason, owners should get as light an engine as possible that has a lot of low-end torque. That is why 2-stroke outboards are often favored by many RIB owners.

Selecting the Right Outboard Engine
RIBs take more horsepower and need strong low-end torque. This boat is powered by twin Evinrude E-TECC G2 300s which have strong low-end torque and fuel-efficiency.

Many RIBs actually draw more water than a similarly sized all-glass or aluminum boat because so much of the beam is the inflatable tube itself, which is not submerged as much as is the fiberglass hull it is attached to. This means more horsepower is needed until the fiberglass or aluminum hull is on plane. Then the vessel flies, due to reduced wetted surface.

The key with RIBs is to get the boat on plane without having to put everyone in the bow to trim the boat while it is building speed. Depending on the size of RIB, we would recommend from 40-hp to 50-hp as a minimum on the small end, say 12’ to 14’. Here, we recommend 2-stroke engines. Large RIBs can have two or three big outboards on their transom and they need them to go fast and carry a load.

In a bit of an extreme example, Revolt Custom Boats, a Dutch builder of custom high-performance RIBs recently announced a partnership with Mercury Marine to power all its boats. The first model in the joint venture is a Revolt 31X powered by two Mercury Racing Verado 400R outboards.

Selecting the Right Outboard Engine
With more RIBs being designed for all-around and even performance use, seeing 800-hp clamped to the stern isn’t all that surprising.

Small Inflatable Tenders and Dinghies. Small RIBs, say 12’ or so, and inflatable dingies perform best when powered by 2-stroke engines – because of the superior low end torque. Typically, when 4-stroke outboards are used in this kind of application it takes a long time to get the boat on plane, if at all, and usually it requires shifting weight to the bow.

2. Aluminum Outboard-Powered Boats

Aluminum boats can be powered by anything from 30-hp to 300-hp, depending on the size of the boat and the mission. Typically, these boats are used for fishing, so the size of the engine depends on the load to be carried and how fast and how far the owner wants to go. We recommend that boat buyers calculate the anticipated total weight of the boat with passengers, fuel and gear, then decide what best cruise speed they want to attain if they plan on fairly long runs.

The engine horsepower on any boat should never be more that the maximum rating on the plate affixed to the boat. This is a USCG requirement.

Selecting the Right Outboard Engine boat
The Alumacraft Edge 185 Sport is a multi-species fishing boat with an aluminum hull.

When equipped with 250-hp or 300-hp outboards, these types of aluminum fishing boats can typically have a WOT speed of 55 mph to 60 mph, or a bit more, with two people aboard. But engines that large and expensive aren’t required on a 16’ to 24’ aluminum fishing boat. Boats in this size range with 115-hp to 150-hp engines typically have their best planing fuel economy in the 23-mph to 28-mph range with these size engines, and have a WOT speed in the high 30s or mid-40 mph range.

Selecting the Right Outboard Engine
Tracker’s Pro Team 175 TXW is the manufacturer’s best-selling bass boat and its aluminum.

Before moving up to a large outboard engine, make sure that the boat and the mission require that much horsepower. Some 90-hp engines on 18’ aluminum boats with two people aboard will perform almost as well at cruise and have a WOT speed in the low 40s.

Typically, a 60-hp engine will propel a 16' aluminum boat at speeds from 25 mph to 30 mph top speed, depending on load.

Check out BoatTEST’s “Aluminum Fishboat” type to get a good idea of what you might need…

3. Bass Boats

These specialized boats are designed for one purpose — bass fishing. Many bass-boat owners treat their boats like collectors of antique cars who pamper their classic (and expensive) automobiles. While virtually all builders of bass boats design them for tournament fishing, most people who buy them actually do not enter tournaments and instead use them for low-key recreation fishing enjoyment.

Having identified at least three categories of bass boat owner (tournament anglers, casual fishermen, and bass boat aficionados), it is not surprising that the power needed for all three purposes would be quite different. Boat builders and engine makers spend millions of dollars each year promoting bass boats powered by large outboard engines, but clearly casual bass anglers can have a satisfyling experience with far less horsepower.

Selecting the Right Outboard Engine
The Z520C is one of Ranger’s tournament-focused bass boats.

Anglers engaged in tournament fishing are going to want the biggest engine on the transom that the boat is rated for, in most cases, and that means from 225-hp to 300-hp. (Be sure to double check tournament rules, some circuits limit the size of the outboards.) But more casual anglers, particularly ones fishing on smallish lakes, have no need for such prodigious amounts of horsepower.

For example, a 2,800-pound fiberglass bass boat powered by a 150-hp outboard will have a MPH WOT speed in the 50-mph range, and will have its most economical cruise in the mid-30s with two people aboard. If your lake is small, perhaps an even lower horsepower engine would serve the purpose. In that case, your major consideration would be finding a like-minded angler come re-sale time.

Selecting the Right Outboard Engine
With a 200-hp Mercury two-stroke outboard, the Nitro Z19 has a top speed approaching 70 mph.

Traditionally, bass boats have been the domain of 2-stroke outboard engines. They have a lot of low-end torque, which makes for fast hole shots.

Check out BoatTEST’s performance tests of bass boats to get a better picture of what you need…

4. Flats Boats and Skiffs

Like bass boats, flats boats are designed for a specific application—shallow coastal saltwater fishing. Flats boats go where the water is typically calm, so like the bass boat, they don’t need much freeboard. And, like the bass boat, their bottoms are relatively flat, like that of a skiff, and if powered by large outboards they can go lickety-split.

Selecting the Right Outboard Engine
The Maverick Mirage 18 HPX enjoys high-speed performance with just a 115 hp outboard. We would like to see a back rest for safety on the helm seat of this boat.

Builders and engine makers often display these boats, which are typically 16’ to 20’ long, with 60-hp to 115-hp engines. A potential owner needs to ask how fast and how far he needs to go on an average fishing trip. The answer may be 50 miles or more, in which case he may well want the extra juice so that he doesn’t spend all of his time traveling to and from the fishing spot.

Selecting the Right Outboard Engine
Skiffs like this Carolina Skiff are known for having plenty of casting deck space.

On the other hand, if an angler will be fishing just a few miles from home or the launch ramp, max power may not be needed. Remember, the heavier the outboard the more water the hull will draft. Again, the best cruise and WOT speeds of the boat should guide the buying decision, given the body of water an angler will be spending most of his time in.

Like bass boat owners, flats boat owners want a quick hole shot to get up on plane fast in shallow water. This is where the low-end torque of a 2-stroke engine shines. 4-stroke engines have weak low-rpm torque. They will not be as quick to plane as will be a 2-stroke engine.

Consumer Caveat: Skiffs and small bay boats can be some of the most dangerous boats on the water if they are overpowered -- and this often occurs. Just in the time span of creating of this report -- 3 months -- BoatTEST had to cancel two tests of flats/bay boats because they were deemed by our test captains to be unsafe. We do not publish tests of boats we think are hazardous to use in normal boating situations.

5. Bay Boats

A bay boat is very similar in function to a flats boat when it comes to fishing in shallow back waters and bays but by comparison, bay boats tend to be larger, and have more deadrise to their bottoms. With this larger hull displacement, and more V in the bottom you do give up a few inches in draft and also the poling platform, which on bay boats is replaced by a bow-mounted trolling motor.

The advantages gained in a bay boat, over a flats boat, are more square footage of cockpit, larger livewells, additional storage under the expanded casting decks and typically a better ride in chop. On calm days, many bay boats can even be used in coastyal locations, something we don’t recommend for a skiff.

Selecting the Right Outboard Engine
The Eastward Coastal 2200 has a high freeboard to handle offshore fishing as well as the bay. Note the high deadrise in the bow and the relatively high freeboard, both of which make this boat a more capable vessel.

If top end speed is of value, the larger bay boat can handle more horsepower plus is capable of some light offshore duty on a good day. When bay boats first made their appearance it was hard to distinguish whether you were looking at a large flats boat or a small bay boat. Now the popularity of bay boats has more and more boat manufacturers adding a bay boat to their lines. The result is that that there are now a lot of choices for the consumer who must match the boat to the body of water where it is intended to be used.

Selecting the Right Outboard Engine
The Blue Wave Pure Bay 2400 represents a popular size in the bay boat market.

In the bay boat industry, bigger seems to be better, both in the length of the hulls and the outboard motors that power them. Common now are bay boats 20’ in length with some of the larger craft as long as 26’. 60 mph top-end speeds are made possible by outboards in the 200 to 300 horsepower range.

Selecting the Right Outboard Engine
The Mako Pro Skiff 21 is a new breed of bay boat, one that can still work the flats, but has the size and freeboard to head farther offshore on the right day.

6. Sportboats, Runabouts, & Deckboats

Bigger is Better. The development of bigger and more fuel-efficient outboards has brought about a resurgence of interest in outboard power for sportboats as more and more builders have made these models available. This development is giving consumers a good option that they largely did not have as recently as five years ago.

Selecting the Right Outboard Engine
This Regal 23 OBX is an example of the new trend to outboard-powered bowriders. As can seen in this image, the outboard engine allows the boat to be beached, something that would be problematical for a sterndrive boat.

When selecting power for a sportboat, perhaps the most important thing to avoid is under powering the boat. Some boat builders and dealers typically will install minimal horsepower engines in the smallest sportboats to keep the total price of the boat as low as possible. They call them “entry level” boats. This package might be sufficient for a youngster just starting out or for a newbie couple, or even for grandpa, but for slalom skiing or hauling a boat full of guests, it is simply not enough.

A single 115 to 150-hp outboard motor can produce reasonable performance for an entry-level fiberglass sportboat from 17'-19', depending on the load. With it, a power boat in this range can have a top speed from 35 to 45 mph, with cruising speeds in the mid-20s.

Larger fiberglass boats will need larger engines and today we are seeing 22' to 25' sportboats powered by 250-hp to 300-hp engines.

Selecting the Right Outboard Engine
Powered by a 300-hp Evinrude outboard, the Four Winns HD 270 OB is a capable performer.

For Towing Sports: Boat owners wanting to tow water skiers and wake boarders should consider engines with strong torque in the lower RPM ranges, because it takes lots of power to get participants up on their boards. And even more power is required when there is a boat load of guests.

For that reason, 2-stroke engines such as the Evinrude E-TEC G2 2-stroke engine, and the Mercury supercharged Verado 4-stroke engine are choices that should be considered.

Cruising: Sportboats that are going to be used mostly for cruising should be powered by fuel-efficient engines with the horsepower capable of satisfactory performance for the loads carried.

Check out BoatTEST.com’s tests of nearly 200 sportboats and deckboats …

7. Center Console, Walkaround, and OB Small Express

Anglers going long distances want to carefully balance fuel consumption, best cruise speed, and range. It is always wise in a small boat to get back before sundown, and that means knowing how fast and how far a boat can go with the fuel left onboard.

Center console boats from 20' to 25' can usually perform well with a single outboard from 200 to 300-hp, depending on load and top speed expectations. Over 25' to 26', twin engines are typically recommended.

Big Single or Smaller Twins? All outboard engines are much more reliable than they were 15 years ago. As a result, many offshore anglers are opting for the advantages of a larger single rather than smaller twins, equaling the same horsepower. Twins will weigh more and burn more fuel at a given RPM and speed than will a single engine of the same horsepower, thus reducing range. On the other hand, some anglers feel more comfortable offshore with redundant power. There’s no easy answer.

Selecting the Right Outboard Engine
The Key West 244 CC can be powered by twin 150-hp outboards or by a single 300-hp engine.

Selecting the Right Outboard Engine
The Scout 350 LXF gets three outboards bolted to its integrated bracket.

Somewhere around 25’ most boats going offshore will be powered by twin outboards, typically from 200-hp to 250-hp. Around 33' to 35’ offshore anglers in center consoles will hang three engines on the transom with anything from 225-hp to 350-hp each. At about 40’ some center consoles and express fishboats start hanging four engines. Whether or not all of this expensive iron on the transom is necessary is a matter for the individual buyer to decide depending on his or her mission.

Make sure you know what octane fuel your large outboard is recommended to run on. Some require 92-octane fuel.

Extra Big Power. While the mainstream outboard manufacturers top out at 400-hp with the Mercury Racing Verado 400R, Seven Marine takes things to another level with its 6.2-liter supercharged, small-block V-8 powerhead that makes 557-hp or 627-hp, depending on the model ordered. It makes that power on 89-octane gas.

Selecting the Right Outboard Engine
The 557-hp version is Seven Marine’s outboard.

For a good idea of the speeds and fuel consumption you can expect for center console look at BoatTEST’s tests…

8. Pontoon Boats

Growth Spurt. For the last decade pontoon boats have been the most popular type of boat on the market. The invention of the tri-toon have made pontoon boats faster so that they can now be used for skiing and towing, in addition to cruising, swimming and entertaining.

Selecting the Right Outboard Engine
This Sun Tracker is one of the most popular family-style pontoon boats on the water.

Most pontoon boats have twin pontoons and these are displacement boats; they can only be pushed so fast and adding big engines will not make them go much faster Depending on how large and heavy the twin toon is, most can be pushed close to their maximum speed with a single 90-hp engine, and many people are quite content with a 50-hp engine driving their twin-pontoon model.

Tri-Toons Are Another Story. Because of their added buoyancy, these boats can get up and plane and typically have WOT speeds in the 40-mph range. Some new tri-toons can go 55 mph to 60 mph, when powered with twin 300-hp engines. There is even one large pontoon boat on the market with triple 300-hp engines. They can be powered with 150-hp to 300-hp single engines.

Selecting the Right Outboard Engine
With a 200-hph outboard and triple pontoons, the Regency 220 LE3 Sport has the get up and go to pull skiers and boarders.

Look at BoatTEST’s tests of pontoon boats to get an idea of how much horsepower you will need…

Better Engines

Every year outboard manufacturers try and look into their crystal balls to anticipate what new products the boating industry needs, better yet what new products the boating public will buy. Sometimes changes in a product line are brought on just for the sake of change, where other times you see real innovation that will make your boating experience better. The real benefit to the consumer is that outboard engine technology has advanced and fuel economy has gone up for most outboard brands.

How Much Speed Does Increased Horsepower Give?

Most buyers are faced with the question of if they buy an extra 50 horsepower, how much faster will the boat go. There is no strict answer because there are so many variables boat to boat. However, in the outboard engine industry engineers use the rule of thumb of 1 mph increase for every 7 horsepower added. While that may be true in some applications, BoatTEST would be more conservative, estimating that for each 1 mph additional, 10-12 horsepower will be required.

How much is too much?

An angler looking to purchase a new outboard, either on the transom of a new boat or to re-power his old reliable craft, should not rely solely on the Coast Guard capacity plate. Just because a boat has a maximum horsepower rating doesn’t mean that you should simply buy a new motor that maxes out the rating. The old adage of buy more motor and use less of it may apply to some boats while other boats actually run better with less than the maximum rated horsepower. Just as you should pick a category and style of boat that best fits your needs, you should also pick an outboard motor that is the best match for your boat and style of fishing.


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