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Advantages of the Inboard Engines

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Discover the rise of inboard boat engines in marine technology. Learn about their history, development, advantages, and impact on modern boating. Perfect for enthusiasts and professionals interested in marine innovations.

Typographical errors, called “typos” for short in the publishing field, are the bane of every editor’s existence. Caused by fingering the wrong key on a typesetting machine or misunderstanding a word coming out of a dictating machine or tape recorder – a typo can alter the meaning of a word so as to make a sentence anything from meaningless to wildly at variance with what the writer meant. People have been driven to fisticuffs as a result of quite unintentional “typos!”

In my own experience as a boating writer, many a time while proofreading articles I have discovered outboard motors transformed into “overboard motors” or “outdoor motors,” and “vee drives” transformed into “wee drives.” Once I even found myself sitting in stunned horror as I witnessed what a few typos had done to a perfectly mundane sentence:

“A powerful ventilator is provided to eliminate the engine air in case of overheating” came out as “A powerful ventilator is provided to eliminate the engineer in case of overeating!”

This puts me into the mood to discuss marine engines, and I just hope the typesetter doesn’t decide to get even with me, after the fashion of any eye for an eye, by changing that into “murine” engines!

But enough of this nonsense. News media suggestions about raising gasoline prices to reduce consumption has had an effect on pleasure boating that seems to be there, but which is nevertheless rather hard to pinpoint and define. You don’t see it plainly and openly, you just sense that it is around.

On one hand, boat and motor sales at one boat show after another have been so good as to pleasantly surprise marine industry people. From what they had been reading in the daily papers they figured there would have to be lean times for them, and they have gone into the show seasons with phony smiles on their faces and their fingers crossed. Their smiles soon became genuine ones and they uncrossed their fingers in order to hold pens to sign one sales slip after another.

On the other hand, published statistics indicate a slight decline, for the first time in many years, in the average size and power of outboard boats and motors, which might be an early harbinger of a trend to lower power in the face of rising fuel prices. And, the number of sailboats has continued to show a steady increase, suggesting that perhaps more people are quietly playing it shrewd by buying boats they can continue to use regardless of future zigs and zags of the petroleum situation.

To fill up vacant space, boat shows have been making it available to assorted boating organizations for educational and attention-catching displays. A number of shows have featured displays of old boats restored by members of the antique and classic boat clubs. In addition to attracting attention, these boats have started many people to thinking about the good ride and low horsepower requirements of older motorboats having long, narrow hulls.

Cruising the aisles of boat shows and reading manufacturer’s news releases, one senses other vibrations that hint that fuel economy is a subject very much on people’s minds even if they don’t shout it from the mast tops. Makers of friction-reducing bottom paints, efficiency-increasing propellers and performance-improving trim tabs find attentive listeners to their spiels. Builders of Boat Outboard Motorsoutboard motors publicize improvements to the innards of their products aimed at using fuel more efficiently. And so on. All this is to the good, for it means we may have come to the end of the era in which the mindless pouring on of more and more horsepower was the normal way of increasing performance.

If there is a trend afoot that can be called clearly visible, it has to be the growing popularity of conventional shaft-drive inboard engine installations in the types of boats hitherto powered by either outboard or stern drive engines. Several firms are now offering boats of this type with such powerplants. Some are prominent companies, others less well-known. But all are attracting interest and buyers.

The stern drive power plant became very popular because of its particular assortment of advantages. Now that fiberglass is the dominant material in pleasure boat construction, we all have to be aware of the fact that what our boats look like has at least some connection with the peculiarities of fiberglass molds.

Here are a few examples. A hull mold for a craft having a long, narrow, sharp bow, such as an old-time naptha launch or a canoe, looks like what you’d get if you covered such a hull with plaster or paris and then pulled off the resulting plaster mold – it will have a deep, narrow hollow up forward that gives the fiberglass boatbuilder problems the wooden boatbuilder would not have. When building in wood, one starts “inside” with the frame and works outboard, putting on the planking and then the paint.

Motorboat on the water
Open-water boating does not need the shallow-water capabilities of stern-drive powerplants, so small conventional inboards are becoming popular. Their bronze and Monel lower unit parts have good corrosion resistance
Source: pixabay.com

But in fiberglass, one works the other way around. The first step is to spray colored resin, called the gel coat, onto the polished surface of the mold. When that cures hard, layers of glass cloth and resin are laminated over it, ending with the innermost layer that is visible from the inside of the hull. It can be difficult or even impossible to spray gel coat and operate resin brushes and rollers in the bow area of such a mold. One solution used by canoe and sailboat makers is to use a “split mold;” it is divided into right and left halves along the keel line and bolted together.

When the hull has been laminated up the halves are brought together and a final application of tape along the keel line binds the sides together. After the split mold is taken off, the gel coat along the parting line has to be smoothed up and polished. In general, builders of mass-produced boats prefer not to become involved with split molds. One of the reasons why blunt, wide, generously-flared bows are common in Use of Fiberglass in Boat Constructionmodern fiberglass powerboats is because the molds for them are so “open” and wide that it is very much easier to do a good and fast job of laminating in them.

But getting back to engines, you will understand that the mold for a boat’s deck and cockpit are even more complicated. Although they are made of one piece of laminated fiberglass, they have many more surfaces, angles and depressions than a hull mold. If a boatbuilder wanted to offer a small cruiser with the option of outboard or conventional inboard engine propulsion, incorporation of a suitable engine box amidships would be objectionable from the outboard purchaser’s standpoint, and incorporation of an outboard motor well at the stern would be objectionable to the inboard purchaser.

Read also: Inboard and Outboard Engines

The stern drive engine enables boatbuilders to offer the public a choice of inboard or outboard power with a minimum of mold changes and expenses – the modifications are all at the stern and are all relatively minor, leaving the amidships and cabin bulkhead of the outboard and stern drive versions identical. Mass-production boatbuaders also like the built-in propeller shaft alignment inherent in the stern drive propulsion unit—they do not have to trust to skilled labor to patiently get an inboard engine lined up perfectly with the propeller shaft, and they do not have to worry about this alignment being disturbed should a hull flex in the course of handling and shipping to a distant boat dealer.

From the boat owner’s standpoint, the stern drive’s tilt-up ability is often of great value. It allows him to own an inboard boat of something above outboard power and size, while retaining the outboard’s ability to operate safely in shallow waters and to glide up onto beaches. A surprisingly large amount of boating today is done on man-made lakes, many of which tend to have a lot of driftwood and submerged stumps in them, so again the stern drive is of value.

But all hands have to admit that the fellow who operates largely on the open sea does not particularly need this tilt-up feature. The stern drive’s lower unit is of necessity an elaborate mechanism containing many parts. When repairs are necessary, it can amount to quite a job. The mechanical simplicity of a bronze or Monel shaft coming out of the bottom of a boat to turn a propeller fitted to its after end just has to have its appeal to the salt water fisherman who does no trailering or beaching, but who heads out for deep, unobstructed water every time he uses his craft.

A reasonable person would say that somebody was bound to try a conventional inboard installation in one of the larger open-cockpit hulls that had been developed by the Florida fishermen for big-water work with outboard power. When it finally was tried, it was found to be practical, and to offer its own set of advantages. Now several firms offer this option.

The space under the helmsman’s console characteristic of the big open fishing outboards—normally occupied by a large-capacity gasoline tank—proved to be an ideal place to put the inboard engine. A minimum of mold problems, for a change. Stern drive power units are based on auto engine blocks, which are large and made of cast iron; a stern drive powerplant can put around twice as much weight on the stern of a boat compared to the large outboard motor. Most of the time that’s all right; you can compensate for it by putting passenger, cabin or gas tank weight forward.

But the console style open fishing boats regularly encounter rough going which the lake and river people inland just do not have to cope with, except very rarely. They don’t want an overly heavy forebody that might tend to “submarine” into big, steep waves when going slow with their bow down. And a lot of weight in the stern combined with a light bow isn’t very good when going with a big following sea, because then the stern does not want to rise quickly and easily to them as they come rolling up from behind.

The conventional inboard installation with the engine block’s weight amidships does have a lot going for it in the serious open-water fisherman. It’s far enough forward to hold the high, flaring bow from “kiting” when going off the tops of waves into a brisk wind, and not so far aft as to hold the stern down against lifting to following seas. Hidden under the amidships console, the engine leaves the after end of the cockpit completely free of an engine box so that the fisherman can use that important area of his boat to best advantage for playing and landing his quarry. Located down under the hull and ahead of the transom, the rudder and propeller are less likely to entangle the fishing line than is a stern drive unit projecting appreciably aft of the transom.

Among the firms offering craft of this type are:

  • Aquasport, Inc.,
  • Chris Craft Corp.,
  • Dusky Marine,
  • AMF Slickcraft,
  • Sea Craft,
  • John Allmand Boats,
  • Karanda Marine, Inc.,
  • Mako Marine, Inc.,
  • Pro-Line Boat Co., Inc.

No listing can be complete, for other firms are getting into the field all the time.

It has to be mentioned that other firms are also offering interesting inboard-engined fishing boats that differ in one way or another from the “console” style made by the aforementioned companies. For several years now the Penn Yan people have specialized in producing tunnel-drive inboard engined craft, including open-cockpit runabouts and small cabin cruisers.

These are all planing hulls which ride on the surface of the water, more or less, when operating at cruising speed, so of course the exact draft depends on whether one of these boats is going slow or fast. However, the tunnel drive does offer the fisherman the shallow-water operating ability of the stern drive combined with the mechanical simplicity of the conventional inboard engine. As experience has accumulated with this type of drive, Penn Yan has incorporated useful improvements in the design of their tunnel and related gear.

Some open-water fishermen don’t particularly care for an all-open boat, preferring more passenger protection from the elements, especially for use in more northerly waters. A lot of bluefish and striped bass fishing is done in the waters off Rhode Island and the islands to the south of Cape Cod. Shorelines tend to be rocky and the bottom just off the beach is also boulder-strewn. This habitat attracts small fish and the large game fish which feed on them. In turn, fishermen are attracted to such waters and they need a boat with certain qualities to operate in such areas. The so-called “Cuttyhunk bass boat” developed in that general area has been taken as the model for a number of modern, fiberglass inboards by some builders there.

Trailered boat
Trailered and ready to go
Source: pixabay.com

Having a low out comfortable cabin with two bunks under the foredeck, the increasingly popular Fortier 26 is one of them. Sprouting from its abbreviated afterdeck is something you seldom see away from Cuttyhunk Island – a tiller that’s connected to the rudder so the craft can be handled from the stern. There’s of course a conventional wheel up forward. A point worth noting is that it’s the location of the engine amidships that makes the location of this tiller and its connecting rods feasible, for obviously a stern drive unit would be quite in the way of both the tiller and anyone wishing to use it.

Incorporating soft-riding, economically-driven semi-displacement hulls, the “Wasque 26” and “Wasque 32” by Vineyard Yachts, Inc., and the “Dyer 29” made by The Anchorage, Inc. are other interpretations of the theme. Made of fiberglass, they are not designed to rise well up on the water’s surface, but instead cut along through it so their fine bow’s can split the waves easily instead of having the planing bottom pound and buck on them. Fitted with moderate engine power, they are capable of thoroughly useful speed, while still being reasonably easy on fuel. Boats like these tend to be purchased by persons who have had a lot of experience with various boats and have come to realize that all that glitters is not gold.

The trailered boat has put the sport of boating within reach of millions who do not live handy to the waterfront. Emphasis on trailerable hulls has more or less forced the makers of mass-produced powerboats to put out hulls that are suitable for trailering. Where planing motorboats are concerned this usually means absence of a skeg. It is worth noting that the Fortier, Wasque and Dyer boats just mentioned are equipped with substantial skegs. Partly to afford needed propeller protection when working around areas known to have submerged boulders, and partly to give good motion and control on big waves.

Incidentally, we ought to mention that the new breed of open-cockpit, console-style inboards from Florida can be trailered. Of course you have to pick your launching and haul-out site with the projecting rudder and propeller in mind—but once on the trailer, the engine weight located amidships in the hull comes right above the trailer’s axle or axles, giving a well-balanced, easily-maneuvered trailer – at the same time utilizing the engine girders molded into the hulls to distribute engine weight onto the trailer supports with a minimum of hull strain or distortion.

In recent years it has been common to encounter items in news media where assorted writers decry the “waste and inefficiency” of the multitude of makes and models offered to the public by a large number of corporations. They would have the government take over management, cut out all the duplication and offer the public a few basic models. We ought to wonder what’s in the heads of such people, for right here in this matter of inboard-engined boats we have a practical and convincing example of how the public is, in fact, better served by the existence of many companies and models.

One man wants to carry one or two persons and a moderate fuel supply for his trips to one kind of fishing area not far from home. Another wants to carry several people, or a fifty gallon tank of gas for offshore work. Very well, these gentlemen can consider outboard motors, the light-load man going for a medium-powered one and the heavy-load man for a more powerful model. Either motor will attach just as quickly to the same make and model of outboard boat.

The man who wants more power, or who feels better with an inboard engine, can take the stern drive if he plans to do a lot of operating in shallow waters or if he intends to trailer his boat and need not worry about having the aluminum parts of a stern drive’s outboard unit immersed for long periods in salt water. And now, with the appearance of these amidships inboards, boat owners who do mostly deep-water work or who moor their craft all season and are wary of electrolysis, can choose from among these inboards and get draft best suited to their needs.

We’ll wind this discussion of inboards up with brief references to assorted matters of general interest. The stern drive people recently had quite a problem dumped in their laps. The gears used in stern drive engines are smaller than the rear axle gears used in cars, yet transmit a similar amount of power. This was made possible by the use of special gear lubricants containing, among other things, whale oil. This oil is naturally “slipperier” than other oils and provided the protection stern drive gears needed. With the hunting of whales being phased out, lest these great creatures become extinct, this useful oil has become unobtainable. A lot of experimenting went into developing substitutes, and so stern drive enthusiasts can now heave a sigh of relief.

The Wankel rotary engine was much in the news a few years ago, but the petroleum situation that has existed these past few years has tended to focus public attention on its fuel appetite, which is at the present stage of development higher than for piston engines of similar power. So, introduction of the Wankel in American automobiles has been put off by the major car manufacturers. If their continuing experiments succeed in lowering the Wankel’s fuel consumption so that the engine goes into mass production for automotive use, it will be a boon to boatmen not long after. Since it is considerably lighter and more compact than the piston engine, it will have obvious advantages for the boatmen, particularly those who like stern drives but would prefer to have less weight in the sterns of their craft.

In the meantime, the choice of boats and motors now available to the boatman is so wide that, as the saying goes, “There’s something for everyone!” You pays your money and takes your happy choice!

Author photo - Olga Nesvetailova
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