Anyone ever dynoed a 20H conversion?

[champ20B]

Do you have any pics of that Karelsen?

The record set in 1999 with a better engine(?) isn't much different than what you set back in 1974.

Kilo* Straightaway APBA 62.163 3/6/1999 Oroville, CA Gooffy Shawn Love Jack Terrell Sorensen Evinrude

62+ isn't bad for a 15hp OMC outboard at all, even with a racing foot ! I wonder though, how those KG4 mercs would work with the conversion stack as a mod? I suppose it could be used just the same.

BTW, I read where the ASH guys in region 12 are bailing out because somebody bought a new engine (a sidewinder), and are regrouping as ACH ( "A" Classic Hydroplane) so they can just run OMCs. Since it is a classic division they want to start up, maybe they might let the KG4 stockers back in too? That would be interesting. I feel bad though, that someone invested in a new engine just to have competitors walk out or not show up because of it. Doesn't say much for sportsmanship at all regardless. I hope this idea doesn't spread across the country. If it does then ASH will disappear with the new 15 SW all together. That aint good.

[smittythewelder]

Since popper Hp officially unknown look at it this way as an estimate. Power is proportional to V^3. From what I recall when racing in the 70's my unconverted 20H in BSH would run about 61 mph, a 20H popper about 66 set up for circuit on a hydro. Running the numbers and assuming 20 Hp for the 20H gives 20 Hp x (66/61)^3 = 25.3 Hp for the popper all else on the hydro being constant including rpm except speed. You can play with other numbers and get maybe 26-27 hp because some of the real good poppers set up right would tic at 67 mph and that gives 26.5 Hp.

All this assumes 20 Hp for the 20H standard so the real answer is?

How did you come up with the speed figures? If they were read off a speedometer in the boat, then they are low because of the drag of the pitot tube. Wouldn't that effect the calculations? Also, how do you factor in propeller efficiency percentage, hydrodynamic drag, aerodynamic drag? This is not to say that a calculation from velocity is necessarily less accurate than various peoples' dyno readings, which notoriously differ from dyno to dyno (they shouldn't, but they do, and this seems to be true all over motorsports).

[zul8tr]

How did you come up with the speed figures? If they were read off a speedometer in the boat, then they are low because of the drag of the pitot tube. Wouldn't that effect the calculations? Also, how do you factor in propeller efficiency percentage, hydrodynamic drag, aerodynamic drag? This is not to say that a calculation from velocity is necessarily less accurate than various peoples' dyno readings, which notoriously differ from dyno to dyno (they shouldn't, but they do, and this seems to be true all over motorsports).

Speed is from my 20H days testing notes, the popper speed is from when I tested with a fellow racer that had one, most likely a Keller or similar pitot device . But it doesn't matter here because the simple basic physics relation is a Relative Comparison of Hp needed to achieve given speed increase all else being equal on set up except the speeds. Not comparing to dyno readings that may be just the power head or whatever. Don't make the relation any more complicated than that.

I have used this relation on many applications to figure what relative change in power is needed to achieve a change in speed, not just engines but drag vs speed, etc, seems to work fairly well but forget getting absolute answers just relative changes knowing any 3 of the 4 values to get the 4th. The accuracy is in the known values to get the unknown. BTW this is the same physics relation that Ken Warby's technical adviser used to estimate the Hp needed to overcome the total drag on Sprite of Australia when Ken set the water speed record of 317.6 mph in 1977, it worked quite well for him.

http://en.wikipedia.org/wiki/Ken_Warby

[champ20B]

Well, whatever a 20H conversion makes.......one thing that can be pointed out, being that a factory spec conversion is allowed in A-MOD, is that a factory spec OMC 22cid/25hp powerhead with closed exhaust (on a stock racing tower of various choice) and racing lower, can easily compete with the merc in this category. Again, that's a 25 hp unmodified powerhead.

Now being that the 15ss Hotrod is officially dynode at between 25 and 26 hp stock, that kind of denotes the point of running pipes or chambers on this engine since again, a 25hp OMC fishing powerhead mounted on the same mid and lower can compete. But maybe its the torque of the 25 that makes up for it if the 15 HR is making more hp with pipes. But the same may not be as prevalent comparing the 20H, so maybe it is about 26HP.

[champ20B]

Well, whatever a 20H conversion makes.......one thing that can be pointed out, being that a factory spec conversion is allowed in A-MOD, is that a factory spec OMC 22cid/25hp powerhead with closed exhaust (on a stock racing tower of various choice) and racing lower, can easily compete with the merc in this category. Again, that's a 25 hp unmodified powerhead.

Now being that the 15ss Hotrod is officially dynode at between 25 and 26 hp stock, that kind of denotes the point of running pipes or chambers on this engine since again, a 25hp OMC fishing powerhead mounted on the same mid and lower can compete. But maybe its the torque of the 25 that makes up for it if the 15 HR is making more hp with pipes. But the same may not be as prevalent comparing the 20H, so maybe it is about 26HP.

Basically what I mean is that if the 25OMC A-mod is 25hp, the 20H popper is 26hp, and the 15ssHotrod is 27+hp, the difference in torque on each motor is what evens them out.....

[DeanFHobart]

Dean I still have a un touched Kamic 48 - 23636 prop. My Dad bought it new in the 50's

Danny,

I still have one also...... Cool.

[DeanFHobart]

Do you have any pics of that Karelsen?

Yes I do..... However, they are stored away and not accessible at the moment. I only tested it once before going to Modesto, California for the Kilos. And just ran it two one way runs to break the record. Ed Karelsen sold the boat right after. I had no desire to do it again. The boat was definately fast in a straight line.
At the time, I had both the 1 - 2/3, 5 mile Competition and Kilo records..... The only records that were available at the time.

[rumleyfips]

All the speeds I quoted were dragging a Keller tube. I set it down as far as I could to get a steady needle. Over the years I bought and sold a bunch of Kellers to get one where the needle didn't wiggle. When trying different parts etc , a quarter of a mile was important and the speedometer had to show it. 4 I/4's was 1 mph.

In the 70's ASH was the only class that ran at it's full potential in competition. Racing speeds were close to kilo speeds. I never figured out why.

[DeanFHobart]

In the 70's ASH was the only class that ran at it's full potential in competition. Racing speeds were close to kilo speeds. I never figured out why.

It was because we ran "Jacked Up" even in competition... By the end of the KG4 / Mark 15 era, I was running between 1" and 1 - 1/8" above the bottom with a three blade all the time. Three blade propellers allowed us to do that.

[rumleyfips]

There were some good ASH's in Region 2 in the 70's; France,Marcell,Webster and more. I don't think I ever saw any of them run a 3 blade, but they all ran real high.