Outboard horsepower measured?

[Buccaneer]

My son and I were out on the lake today test running the Merc
Mark 6 I went thru last year. Trolled good, and ran out a whopping
9.7 mph with the wind, and 7.3 mph against the wind 😆
Anyway, my son asked me how they determined horsepower on old
outboards back in the day. I told them I wasn’t sure.
Was it purely mathematical, or some kind of dynamo? If so, how
did it hook up to the outboard?
Are modern outboard hp measured in the same way?

Prepare to be boarded!

[r-c]

Before about 1984 or 85, the hp was measure at the powerhead with the exhaust just blowing into the test cell on usually a water brake dynometer. Since that change in the mid 1980’s, they measure at the prop shaft. This takes in the loss of the gear case and the advantage of any tuned exhaust.

[garry-in-michigan]

Back in the day English coal mines seeped water into the coal mine shafts. They used horses the pull the coal and water out. It was determined a good horse could pull 33,000 pounds of coal or water out of the shaft. When steam engines started to take over they were rated on how many horses they could replace. Hence the term "Horse Power." Steam engines could be figured mathematically by knowing the working steam pressure, area of the piston and length of the crank arm. Gasoline engines were more complicated. They found that adding a wheel to the crankshaft with a break to absorb the power, you could measure the force on the break with a lever attached to a scale. This was called Break Horse Power, and it was how early outboard were rated. Just when we thought we had everything settled, it was discovered horse power sold motors. Suddenly it was up to the engineers to squeeze every last drop of power out of there test engines. It became common in the early ’30s the round up to the next HP if you managed to get past a HP mark. Unfortunately production motors could not be assembled with the same care and frequently fell short.

Most outboarders didn’t notice, because they always thought they were going faster than they actually were. However Some speed enthusiasts noticed and complained. Soon the complaints mounted, and caused the major motor manufacturers to come together to solve the problem. They formed the National Outboard Association in 1933. The agreement was that representatives of the competing companies would come in and chooze three motors at random to be tested for horse power. The averaged power of the three would be the cerctified power of that model. Over night, some models lost three horse power. Evinrude and Elto hung brass medallions on there models proudly proclaiming "NOA certified horsepower". From what I have seen on Ebay, some must think those medallions are gold. That’s the way it was until World War Two, which put civilian outboards on hold for the duration . After the War the pent-up demand for outboards was fantastic. The sequestered 1942 models were relabeled and quickly sold.

Meanwhile there was frantic retooling to build the motors that were on the drawing board for peaceful times. Using wartime research & development, money and experience from war contracts, Everyone was ready to build the outboard of the future. There was little time to certify horse power as the Magazine advertisements were done almost before the motors were assembled. The Martin 60 was estimated to put out six horse power. It tested at seven and a half. Evinrude had not put there prewar gearshift patent into service. Johnson used it for there QD model, Evinrude used it on there Fastwin. Mercury used there Target Drone motor experience to build some truly high performance outboards. Carl K thumbed his nose at NOA and under rated his new outboards. After that it was whatever marketing thought the market would bare. Finally the government stepped in and required that rated horse power be taken at the propeller shaft. – was that 1984? . ❓ . . . . 😀

[foot_doctor]

My Dad, Larry Thomas was hired by Denny Watkins, the director of OMC Research in Milwaukee to build their first large engine dyno. The project took him about two years on their premises. When it was completed, they hired him to be their facilities manager. The dyno he built used existing electric power company lines as the load bank. It simply generated 60 cycle current that was fed back into the electric company’s grid. As far as I know all of the tests run on that dyno measured crankshaft horsepower, not propshaft. R.T.

[Buccaneer]

Thanks all for the interesting information and history lessons!
It would be neat to see some vintage photos of outboards being dyno’ed.
I started a test log for the outboards I’ve fixed up and am testing on the
lake, mostly to keep track of how well they performed and what may
need tweeking. Perhaps I should dyno test them too……. or perhaps
I’ll just record the GPS speed on each one! 🙂

Prepare to be boarded!

[crosbyman]

when I visited (1996) a museum in England (black country of Birmingham) they had about a 2hp engine (steam) weaker than today’s lawnmowers
The "steam chamber" was about 8 feet wide and 8 feet high . it collected steam which was then cooled to produce an up/down motion .

nothing to put in your row boat 😎

Joining AOMCI has priviledges 🙂

[dan-in-tn]

Just something to add to Garry’s comments. You don’t run/race dynomometer. Just more horsepower doesn’t always mean more speed on the water/boat. Application, setup, prop, & hydrodynamics play a big part in how fast you go. Now back in the old days Karl just cheated with more horsepower! Mercury has always done a good job with a smaller engine (cu. in.) vs gearcase design and getting everything out of their designs. Sometimes at the expense of longevity, but still fast if setup properly.

Dan in TN

[green-thumbs]

James Watt determined that lifting 33,000 pounds 1 foot in 1 minute was a little more than the best horse could do. He rated engine’s capacity in "Horsepower" because customers could understand the power of a horse but not math of engine power. Early steam engines did not have to be very efficient to replace human or animal power. A steam engine at a coal mine could pump out water continuously 24/7 using coal from mine to fuel boiler. Hoisting coal up out of mine could also be done by a steam engine supplied with steam by same boiler. The efficiency of iron wheel rolling on an iron rail led to horse powered railway to haul coal to market…eventually steam engine replaced the horse there also. Not even a super horse could work as hard or as long as a steam engine of 1 horsepower…Watt sandbagged his power rating.

[garry-in-michigan]

Steam chamber – That’s about the size of a stall for a horse, but it probably burned more hay. Using animals for power still generates green house gasses, but does create jobs. Someone has to pickup those horse apples off the street, they attract a lot of flies. Yes, I remember when Mr. Landcaster would deliver our milk in a horse drawn wagon. The horse liked me because we had an apple tree in the back yard and I would give him Apples. He ate them seeds and all. In the days of the Ice Box, the ice man would deliver it (by horse drawn wagon) in 25 pound blocks. Our first Refridgerator was powered by natural gas. Air conditioning was by electric fan. Shoveling coal into the furnace, taking out the ashes – That was Detroit in the "Good Old Days" . . . . . 😡

[garry-in-michigan]

I remember Denny Watkins as a very nice man who was always willing to answer my questions. Dad worked in experimental Engineering with Denny and "Irgie" Irgens from 1929 through 1931. Dad stayed in contact with Denny as long as he worked for Evinrude. He was a big help in our racing endeavor, digging through the dusty bins of the parts storage section to find what we thought would be helpful. Although Steve Briggs was dead set against racing, Jim Webb wasn’t’ and forwarded a copy of Dad’s weekly report on racing in Michigan to Ralph Evinrude. Ralph wanted to have Evinrude competitive, but was out voted on direct support by the OMC team. – – 🙂

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