A Duckworks reader inquires:

If you disregard the issue of money, the purchaser of a new outboard motor has an almost unlimited choice of brands and models of engines available. It is rarely necessary for the buyer of a new outboard to make any compromises as to horsepower or features; the buyer can purchase the exact model outboard that best fits the needs of a particular boat.

The purchaser of a used outboard, however, has a much more limited choice of engines available; in effect the purchaser of a used outboard is limited not only to the choices made by the original purchasers of the outboards, but also by what particular outboard motors are on the market at any particular time in a particular area. . The result is that the purchaser of a used outboard is nothing like the buyer of a new engine. Being less discriminating in one's requirments will increase the likelyhood of locating a suitable engine.

A 1957 Johnson 18 hp; the first year of 18 production. Note that this version has electric start; if you want electric start, be prepared to pay a big premium as any small electric start outboard is a "high demand" item. A properly-tuned 18 is easy to manually start, anyway. Note the pressurized fuel tank. (click images to enlarge)

Although many would consider horsepower to be the first factor in the
selection of an appropriate used outboard, I consider the matter of shaft-length to be more important. As discussed in the shaft length column, the older an outboard is, the less likely it will be that 20-inch versions will be available. For engines of under about 25 horsepower, 20-inch engines are extremely rare except in some areas that have high concentrations of sail boats, and even in that case the 20-inch versions will most likely be of under 15 horspower, with "ski boat" outboards of 40 hp and up being most likely 20 inch versions, leaving most engines of 20 to 35 horse power being of 15 inch versions.

I have only the small-scale drawings of the Clarence River Dory posted on Duckworks to reference, but it appears to me that the dory is designed to use 20-inch shaft engines*. The written discription does make mention of "short-shaft" engines, although again there is the problem of exactly which length is considered a "short shaft" when there are three lengths available. Perhaps the design can be built either way, but if one intends to use an outboard manufactured before, say the mid-70's, a 20 inch version is going to be much harder to locate than a 15 inch version in the 20 to 25 horsepower range.

This 1965 Evinrude 18 is almost identical to the '57 Johnson 18 above except for obvious differences such as hood design and paint, and less obvious differences such as a fuel pump (no pressure tank) and a fixed high-speed jet in place of the adjustable high-speed needle valve.

I would add that if I were to build this boat with a 15 inch transom, I would make such provisions so that the transom could be 'built up" to 20 inches at some point in the future. If I were ever to purchase a new outboard motor of 20 to 25 hp, for use on this or any boat, I would be inclined to purchase a motor with a 20 inch shaft, as many new boats that use this size outboard have 20 inch transoms either standard or available, and most home-built designs can be adapted to use a 20 inch engine.

If the decision is to use a 15 inch engine on the Clarence River Dory, then the next consideration is the horspower. The designer indicated 25 hp as the maximum for the craft, and with a wealth of experience running 10 hp and 18 hp engines on my own 18 foot flat-bottom boat, with a short trial run with a 25 as well, I whole-heartily agree that 25 should be the maximum. The Duckworks plans catalog indicates that the bare boat should weigh approximately 308 pounds; Knowing that home-boatbuilders generally "over-build" their boats (me too !) I am going to make a guess at 350 pounds for the bare boat. Adding outboard, fuel, and gear would bring the weight to about 650 to 700 lbs, depending on the amount of "gear," of course. Add two people and the boat should weigh in, say, at 900 to 1000 lbs. According to a truck scale, my 18 footer with all gear aboard but no people weighs right at 1000 lbs, so I believe it to be comparable to the dory as far as horsepower requirements.

1970 Evinrude 18 differs from the 1965 mostly in paint and decals.

I have found an 18 hp outboard to be more than adequate for my own boat, and I would probably be satisfied with 18 hp on a Clarence River Dory as well. As OMC (Outboard Marine Corp., my outboard motor manufacturer of choice) made Johnson and Evinrude 18's from 1957 until about 1973, there should be a fairly good selection of used engines available, although keep in mind that outboards of between 10 and 20 hp are in higher demand by anglers than engines of higher and lower hp, and so the price may be affected. As 18's were generally too large for sailboat use, and most powerboats built during that era suitable for 18 hp engines were built with 15 inch transoms, it will be rare to find a 20 inch version of an 18. Also keep in mind that 18's built before about 1960 will utilize a pressurized fuel tank unless converted to a fuel pump.

From about 1969 until the early '70s, Both J. and E. sold a 25 hp version of the 18, but these engines are not seen too often, possibly because the attempt to extract 25 hp from their 22 cubic inch powerheads overstressed the engine, shortening it's life. An updated 25 was introduced in 1975, but those models would be "new-enough" to command some fairly high prices on the used engine market, plus by the mid-'70s electronic ignition was making it's appearance, and I always recommend avoiding electronic ignition.

1973 18 was just about the end of the line after 16 years of 18's

From the mid-to late '60s Johnson (but not Evinrude) marketed a 20 hp engine but as far as I can tell it was merely a re-labled 18.

If you are willing to accept a little less than 18 horsepower, the '55 and '56 J. and E. 15's are good engines, with the note that the 1955 used a weaker recoil starter design than the 1956, and both used the pressure tank. I would not recommend a 15 earlier than 1955 for the cheap power seeker; there are a number of differences in the earlier motors. The Gale 15 hp outboards of the late '50s up through 1963 (the last year of Gale production) are very good engines if the horsepower is right for your application.

Through-out the late '50s and into the '60s, OMC had kind of a "hole" in it's outboard horsepower line; the next step up in horsepower from an 18, disregardlng the "over-stressed" 22 cubic inch 25 hp introduced in 1968, was the much heavier and physically larger "Big Twin." In 1957, the first year of 18 production, the big twin was 35 hp. In 1960 it went to 40 hp. This left quite a gap in horsepower. In an attempt to fill that gap, OMC brought out 28 and 33 hp engines in the early/mid '60s. Although these engines filled the "horsepower gap," they were based on the Big Twin design and were the same physical size and weight as the big twins. And anyway, any of the the 28's, 33's, or 40's would be way too much power for the Dory.

1971 25 hp was basically just an ordinary 22-cubic inch 18 that was "wound-up a little tighter." I don't see too many of these 25's around, but if you find one in decent condition, it will be about the lightest, most compact 25 hp package you are going to find. Just don't count on it to pump out that 25 hp for long periods of time.

Another concern, at least here in the U.S.A., is that often a person's homeowner's liability insurance will cover a powerboat with no more than 25 hp; if you want a larger engine, a separate insurance policy will probably need to be purchased for the boat, as would be needed if you wanted damage and theft coverage in addition to liability coverage.

Early Big Twins, dating from 1950 to 1955, where 25 hp and also a bit lighter (not much) than the later big twins, but these engines are a bit older than I would recommend for the cheap power seeker, with the possible exception of the 1955 25 hp which is a good solid engine but virtually no lighter or smaller than the succeeding 30 and 35 hp Big Twins.

Gale made a 25 hp version of the Johnson and Evinrude "Big Twin" that was similar to the 35 hp version shown here. the Gale 25 would be heavier and bulkier than the 25 hp version shown in the previous illustration, but would also be a more "robust' engine.

One alternative might be a late '50s / early '60s Gale 25, a derivative of the Big Twin design. A 25 Gale with manual start (no electric starter) would not be too difficult to hand start (actually none of the Big Twins are THAT hard to hand start) and the weight savings from forgoing the electric starter would be significant. One comment; one often hears people talk of "heavy old outboards;" these old outboards are actually no heavier, and often lighter, than modern 2-cycle outboards of the same horsepower, and are considerable lighter than modern 4-cycle outboards. They are, however, often physcially larger than modern engines, giving the appearance of great weight, an appearance that can be deceiving.

If I were building a Clarence River Dory, my choice would be a 15 inch version of the OMC 18 hp for most uses; if I expected to operate the boat very heavily loaded, I might look for either a 1955 25 hp manual start OMC and convert it to use a fuel pump (easy to do on a Big Twin) or possibly a 25 hp Gale, which would already have the fuel pump.

Transom mounting dimensions straight from the owner's manual for the '57 18 hp Johnson.

Anyway, that's my opinion.

And I always have one.


Max