Jim Michalak's Boat Designs

1024 Merrill St, Lebanon, IL 62254

A page of boat designs and essays.

(15 September 2016) This issue will look at old outboard motors. The 1 October issue will take a look at the D'Arcy Bryn design.


Fellow Messers,

July 4th is behind us and mid-September is closing fast. We just wanted to send a short reminder that the 24th occurrence of the Lake Monroe Midwest Messabout will be September 16, 17, & 18 -- mark your calendars.

Go to https://sites.google.com/site/lakemonroemidwestmessabout/home for additional information and feel free to drop us a line if you have any questions. If you're planning to attend, and want us to add your name/boat/homeport to the website's "Who's Coming" list just send us an email.

Hope to see all of you in just a few weeks. We have the ice cream maker standing by!! Pass the word to all your boating friends. Regards, John & Susan McDaniel



is out now, written by me and edited by Garth Battista of Breakaway Books. You might find it at your bookstore. If not check it out at the....


...which can now be found at Duckworks Magazine. You order with a shopping cart set up and pay with credit cards or by Paypal. Then Duckworks sends me an email about the order and then I send the plans right from me to you.


David Baldwin's Mayfly16 crew turned pirate on him...



Contact info:


Jim Michalak
1024 Merrill St,
Lebanon, IL 62254

Send $1 for info on 20 boats.



Old Outboard Fuel Consumption


Max Wawrzyniak, the old outboard guru, has written many times about the wonders of older outboards. After about 1950 the modern outboard took form with its easy starting, full gearshift, and noise and vibration isolators. Many used pretty simple and reliable and cheap technology such that an ordinary guy could fix one with a few tools. The automotive world was similar at the time and most fellows with cars of that vintage can still look under the hood, identify everything that is under there, and fix it. But just as those classic cars are gas guzzlers, so it is with the classic outboards. And as with cars that simple fuel hungry technology was used pretty much unchanged into the 1970's.

Although all the motors used were old, all except the Johnson 10 looked to have been used very little before I got them. There was a boating boom in the mid '50's and a lot of motors were made and bought and used a few times before going into storage for decades. The Johnson 10 was an exception in that all if its linkages were well worn and I suspect it has seen a lot of miles.

I made no attempt to lean these engines out to get improved fuel consumption. All were at the tune that gave good overall operation.


To do the tests in what I think is a halfway scientific way I made up a new "fuel system" with a clear plastic bottle. The bottle is a common soda bottle that you find everywhere. The bottle suits because the center 2/3's is a straight cylinder. This one measured 2.70" in diameter in the straight area. A US gallon is 231 cubic inches, so an ounce figures to be 1.80 cubic inches which would be .316" depth in the straight section of this bottle. I put a piece of tape along the length of that section and marked off 12 ounces. A standard fuel hose and primer bulb is inserted through a hole in the cap and a tiny vent hole is drilled there too. So if this tank is held vertical as the motor draws out fuel you can read pretty well the fuel use in ounces. I would say it is accurate to about a quarter ounce in real use. Smooth water is needed for testing since sloshing in the bottle makes for difficult reading.

The fuel use is timed with the common digital wrist watch set to the stop watch mode, very very accurate.

The speed of the boat is measured with a gps. I suppose the speed here is approximate since holding the boat to within 1/10 mph is difficult over the few minutes it takes to do each run although the gps seems to have no trouble measuring to that degree.

The boat used in all the tests was my AF4 at about 800 pounds total weight. In general this boat goes with little wake until about 6 mph which might be considered the "hull speed". I think it needs about 3 hp to go that fast. Then it starts to drag a big wave until it begins to plane fairly cleanly at 10mph. It needs about 7 or 8 hp to plane at 10mph. I think there is little future in trying to operate AF4 between 6 and 10 mph. So if you don't need to plane 5 hp will allow you to run at 6mph at a comfortable part throttle. And if you want to plane I think it takes 12hp to run it at comfortable part throttle at 12 mph. I think the best option for most would be about 15hp which would allow you the same cruise with another adult on board. Once you start to plane, weight counts for a lot. When my AF4 first was launched it was empty and stripped down at less than 500 pounds total, about 650 with me in it, and it went 17 mph with the Johnson 10. Now it is 150 pounds heavier and the same motor maxes out at 14 mph.

Tests were done like this. The motor to be tested was run a while on the regular tank to warm it up and get its fuel system full. The test tank was prepared and full beyond the 12 ounce marking. Once in the test area the motor was switched to the test tank and the primer bulb pumped hard. The primer bulb holds a large amount of fuel and you need to allow for it. The motor was run up to speed and when the fuel level in the tank had dropped to the 12 ounce mark the clock was started. After the motor had run 4 or 8 ounces, enough to get a valid time, the clock was stopped and the consumption for that run figured. I think the results are pretty accurate. The only problems were with occasional rough water that caused sloshing in the tank and oddly enough, difficulty with readings when the bottle was nearly empty. I think what was happening was that the motor begins to draw fuel out of the primer bulb and not out of the tank such that you motor on for a few minutes with no drop in the tank. So I stopped taking data if the tank dropped below 4 ounces.


An aircooled motor made by Clinton about 1970. Always thought it burned 1/2 gallons per hour at all speeds. Here are the results that about confirm that.


Also from about 1970. Made by Eska I'd say with a Tecumseh air cooled power head. Hard to start sometimes but once going has good power and uses little fuel.


From about 1956. A modern motor with noise and vibration stoppers. Good running and good power but always thought it used a lot of fuel. The motor guru keeps telling me there is something wrong with it but won't tell me what it is.


From 1956 or 1957. Made by Gale which was part of OMC so it is essentially a Johnson or Evenrude but it doesn't have the modern noise and vibration stoppers. Otherwise a very good running engine. I did not run a test at 8mph but I'll bet the fuel consumption would dip to its lowest there as it did for the Johnson10.


From about 1960, sold by Montgomery Wards but made by Gale which was part of OMC. Very modern with full noise and vibration stoppers. Again, no test at 8mph but I'll bet the fuel consumption would dip to its lowest there.


We get this:

With the smaller motors the Sears is noticably the better of the two, especially considering it has a lot more power than the Sea King. The Sea King starts easier, an important factor with a motor that is supposed to be a back up. Remember, AF4 won't plane with these motors.

The results with the larger motors are interesting. I did not show it but when I ran these motors at idle in neutral they all burned about 6/10 gallons per hour sitting still. There is no point in slowing down your boat to get better fuel milage with any of these. The faster they go, the better the fuel milage. I did no runs at full throttle but I would expect the miles per gallon would be the best at full throttle! On the other hand the consumption is actually fairly constant and from a fuel planning point of view speed really doesn't matter much (as long as the motor is in gear). As expected the Johnson 10 is the worst although I think that may be just a quirk of this particular motor. The results of the 12 and 15 are pretty consistant.


...seem to get about twice the fuel milage as those above. One good data point is John Bell's AF4 "Mr. Moon" which has a new 15hp Mercury four stroke. He carries only 3 gallons of fuel and says it will take him 50 miles, cruising at about the same 12 mph that I prefer with mine.! His top speed is about 20 mph, a shade higher than my AF4 with the SeaKing15. The guru says that newer motors should indeed have a bit more power in reality since a few decades ago motor makers agreed to take the power tests at the prop shaft and not at the power head as with my oldies. Thus my oldies lose, they say, about 10% of their power in getting to the prop due to the gear train and the water pump.

And Asley Cook has a new Tohatsu 30 two stroke on his Dorado which is about the same weight and size as AF4 but modeled more for rough water. He says that motor has run 7 hours on the standard 6 gallon tank. And I think he is cruising a bit faster than we are in our AF4's.

I think new motors in this range cost $2000 to $3000, compared to about $100 for my oldies.




Philsboat is essentially an IMB with the nose extended to a pointy bow. The width and multichine configuration are the same as IMB's. The cabin is 3" deeper because Phil is at least 3" taller than most of us. In a boat with a Birdwatcher cabin like this one added depth to the cabin makes it safer in that the righting forces in a knockdown are greater. That would be true of any boat if the center of gravity did not move with the cabin roof but with the normal cruiser adding depth to the cabin also means raising the crew deck up so the folks can see over the raised cabin. And that means the CG is elevated too, and then all bets are off concerning self righting. But with a boat like Philsboat eveyone rides down low inside looking out through the windows.

Here is a photo of Bob Williams' IMB:

In addition to the pointy bow and added headroom I added what I hope is a serious motor mount. Probably 3hp will drive it as fast as it will ever go and that at part throttle. But the motor well gets to looking pretty large even for such a small motor. For one thing it must be deep to put a short shaft motor on a deep stern like this so I ran it straight down to the boat's bottom. Working on the motor down it its well will be about impossible and you might need to keep an eye on your knuckles when you pull the starting rope. And the well must be surprisingly wide to allow the motor to swivel in steering although the usual case here will be to keep the motor locked straight ahead and steer with the tiller. The wide well pushed the rudder off center and you need a crooked tiller or rudder linkage to make it all work. I opted for a simple but crooked tiller.

I also added low seats like those I saw added to the two IMB's that came to the Lake Conroe Messabout. Pretty much the same as what I have in Scram Pram where the seats do double duty as water ballast tanks. Philsboat seats could easily be converted into water ballast tanks also but the IMB capsize tests imply the ballast isn't needed.

The sail rig uses a balanced lug, 113 square feet and the same as that of a Bolger Windsprint.

Philsboat uses taped seam construction. Five sheets of 1/4" plywood, five sheets of 3/8" and three sheets of 1/2" plywood.

Actually the size and material list for Philsboat are about the same as that of Scram Pram. So which boat would be better? Take Philsboat if you are a pointy bow guy. It should be better in really rough water. On the other hand Scram is wider and roomier. It has a flat step through bow that will splash and spit in rough water but makes beaching a very nice experience.

Update, 2007. Chris Feller completed his Philsboat, probably the first prototype completed, and brought it to the 2007 Rend Lake Messabout. Very well made and to plans except he used the 91 sq ft lugsail he had on hand for his AF3, with some mast rake changes he calculated with his "sail area math". Sailed correctly rigtht off the drawing board, so to speak. We had a chance to use it for a few really nice days. In a good sailing breeze, say 10 to 15 knots with occasional whitecaps, our gps bobbed between 5.5 and 6mph for two hours of reaching as we crossed back and forth on the big lake. When I used the Philsboat I thought it was probably just as easy to enter from a beach as the blunt bowed Scram. The front deck is about 2' high so you can sit on it and swing you legs around onto the deck and then into the cabin.

Chris is a big boy but there was plenty of room inside for the two of us and more. Rumor has it that at the campsite the night before Chris slept in the Philsboat on the trailer with an airconditioner in the front hatch plugged into the campsite power. So the boat is plenty big in the way most people would use it.

The stern layout has the motor in a small well to one side and the rudder offset to the other side to give the motor room to swing. There is no linkage to the tiller, the tiller is simply "unstraight" so that is falls on centerline at the skipper's hand. Seems to work well and is quite simple. Chris uses a 2hp Honda which has a fairly large cowling for its size and must be rotated 180 degrees to grab reverse. He said the motor well size is a bit too small for that. Karl James had the same problem with his Jewelbox a long time ago and simply cut away the side of the hull in top of the motor well region - after all it is just there for looks. Chris said he tried the boat under power and found it went 6 mph max, just like under sail. No surprize to me. My Birdwatcher also maxes out at 6mph under 3hp and under 5.5 hp. This sort of hull will only go so fast. Add more power and you just dig a deeper hole and make a bigger wake - you won't go faster. But sometimes more power is nice on a windy day.

(As an update, Chris has brought his Philsboat to several more Rend Lake meets. In 2008 the meet was very windy and Philsboat got a full windows wet knockdown with Chris and Tom Hamernik on board. She self righted with no issues and they kept right on sailing, but Chris confessed he has 100 pounds of lead shot under the seats. Also he is using a 3hp vintage Johnson which he says is quieter and smoother than the Honda.)

You might recall from the Prototypes section recently that there was another Philsboat being built in California. That one last I heard was about to be launched. Has more changes from blueprint than Chris's boat but still is pretty true to form. Seems to be known as Bumble and made by Rex Meach.

And in New Zealand Rob Kellock has been sailing his with a junk rig. He has been knocked down a couple of times and self righted as planned:

Plans for Philsboat are $45.


Prototype News

Some of you may know that in addition to the one buck catalog which now contains 20 "done" boats, I offer another catalog of 20 unbuilt prototypes. The buck catalog has on its last page a list and brief description of the boats currently in the Catalog of Prototypes. That catalog also contains some articles that I wrote for Messing About In Boats and Boatbuilder magazines. The Catalog of Prototypes costs $3. The both together amount to 50 pages for $4, an offer you may have seen in Woodenboat ads. Payment must be in US funds. The banks here won't accept anything else. (I've got a little stash of foreign currency that I can admire but not spend.) I'm way too small for credit cards.

We have a Picara finished by Ken Giles, past Mayfly16 master, and into its trials. The hull was built by Vincent Lavender in Massachusetts. There have been other Picaras finished in the past but I never got a sailing report for them...

And the Vole in New York is Garth Battista's of www.breakawaybooks.com, printer of my book and Max's old outboard book and many other fine sports books. Beautiful job! Garth is using a small lug rig for sail, not the sharpie sprit sail shown on the plans, so I will continue to carry the design as a prototype boat. But he has used it extensively on his Bahamas trip towed behind his Cormorant. Sort of like having a compact car towed behind an RV.

And a Deansbox seen in Texas:

Another prototype Twister is well along:

D'arcy Bryn is done and sailing here on its first voyage, on the Texas 200. I never suggest you should test a new boat on a trip like this but it worked this time. I will print a full story in a future issue.

The first Jukebox3 is on the (cold) water. The mast is a bit too short - always make your mast too long. A bit more testing will be nice...

A brave soul has started a Robbsboat. He has a builder's blog at http://tomsrobbsboat.blogspot.com. (OOPS! He found a mistake in the side bevels of bulkhead5, says 20 degrees but should be 10 degrees.) This boat has been sailed and is being tested. He has found the sail area a bit much for his area and is putting in serious reef points.






1oct15, Center of Gravity, Larsboat

15oct15, Hullforms Model, Jonsboat

1nov15, Port Aransas2015, Piccup Pram

15nov15, Hullforms Results, Caprice

1dec15, Sail Area Math, Ladybug

15dec15, Sailing For Nonsailors 1, Roar2

1jan16, Sailing For Nonsailors 2, OliveOyl

15jan16, Sailing For Nonsailors 3, Robote

1feb16, Sharpie Sprit Rigging, Laguna

15feb16, Trailering Plywood Boats, IMB

1mar16, Hollow Spars, Slam Dink

15mar16, Bulkhead Bevels, Frolic2

1apr16, Capsize Lessons, RiverRunner

15apr16, Wood Vs Aluminum Spars, Mayfly16

1may16, Scarfing Wood, Blobster

15may16, Prismatic Coefficient, Roar2

1jun16, Figuring Displacement, Mayfly14

15jun16, Rend Lake 2016, Mixer

1jul16, Ballast Calculations 1, Dorado

15jul16, Ballast Calculations 2, Robbsboat

1aug16, Ballast Calculations 3, AF4

15aug16, Taped Seams, Cormorant

1sep16, Butt Joints, Vireo


Mother of All Boat Links

Cheap Pages

Duckworks Magazine

The Boatbuilding Community

Kilburn's Power Skiff

Bruce Builds Roar

Dave Carnell

Rich builds AF2

JB Builds AF4

JB Builds Sportdory

Hullform Download

Puddle Duck Website

Brian builds Roar2

Herb builds AF3

Herb builds RB42

Barry Builds Toto

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