Horsepower-past-present

[TRADER]

I would be interested in hearing about the horsepower levels of OLD versus NEW in all the APBA and AOF and other classes of outboard racing.

What kind of realistic horse-power could you get out of 20cu.in-40cu.in.-60cu.in motor in race trim. Not B.S. figures, but genuine Dyno numbers... Then and Now...

What major innovations were responsible for the biggest power gains, and why...

Port timing

Large bore/short stroke. Small bore/long stroke.

Compression ratio's on gas and alcohol...what's deadly

Besides setup and prop selection, best motor and why...


...trader

[Raceman]

I doubt that you'll get the answers you're looking for, for several reasons. One of the biggest is, there were little or no dyno number "then".

In going all the way back to the earlier times, certainly the change to loop charging from the old crossflow designs would have to be considered among the most significant advances. After that time, port design more so than just timing itself has obviously made huge differences in output.

There's been a lot of speculation on what kind of HP older outboards put out. Nowdays we think of horsepower in terms of what's at the propshaft. In the older ratings, they were generally stated in gross, or crankshaft horsepower. This change, along with the marketing departments of the manufacturers playing games with the numbers contributes to the mystery.

One other thing that throws contrast in to the mix is the inconsistencies of presently available prop shaft dyno's. While they seem to be fine for measuring relativity (before and after mods, changing from one engine to another, etc, etc) many people feel that they're less than totally accurate in terms of accurately measuring horsepower.

[Oclassracer]

My MacMinerelli 125cc(7.5ci) engine came with a crank hp dyno sheet. 46 horse power at 13000 rpm on methanol and castor oil. The engine is very tractable and pushes an 11 foot hydro to a GPS indicated 80 mph. One advancement it has is the PVL brand of ignition that is always changing the advance for the specific engine rpm.

[Mark75H]

Thanks for the information on the Mac, Oclass!

Don't get me wrong, I would love to see this type of real information, but I agree with Raceman, I don't think we will ever see it. For example: what would we compare the 125cc Mac to? I can only think of two older 125cc racing outboards. One I seriously doubt we could get an owner to take one apart for a run on a crank dyno; the other I don't know of a single example running or not.

In the past the motor manufacturers did not release accurate figures or dyno charts. I can only think of 2 motors that I heard the actual hp quoted on......the X-115/GT-115 at 116.5 and the McCulloch 75 at 75.2. I know this is very different from cars, motorcycles, PWC's and snowmobiles, but it is just a fact we are stuck with. You could compare old speed records, but speed records are affected by boat, prop and set up as much as motor hp. Some speed record increases are due to rule changes allowing lighter boats or different boat construction.

Consider the enormity of recreating the data now: finding mutliple original versions of each old motor and a facility to do the testing. Doing the tests on more than one dyno kills the direct comparison. Doing tests on one motor only introduces the possibility of testing a dud or worn out motor. Even some famous motors have no running original example to test.

[TRADER]

I am astounded for the second time, on the output level on a little MAC. "6" horsepower per cu.in. is incredible. In a conversation, some time back, with Mike Striker, (Findley Ohio) former USAC Midget Champion, he told me that he could get 36 horsepower out of a pipe, on some of the little Macullough's he was running on the Indy speedway go carts he was building. I was impressed, as he is very modest, about making such statements.

I was surprised, about the lack of response to this question. Every day I have people walk into my shop and tell me how much horsepower they are making in their race car / street rod. I correct some and ignore others. But here........... I can't call you a liar, because I don't know any better. The people here seem to be more realistic about the facts, than people I normally deal with. I'm impressed by that... Thankyou...

However, there has to be some sort of generalization, about what can be expected from a particular motor, stock as compared to race trim. I find it difficult to believe that a stock outboard making 1+hp per cu.in, would only be capable of the same power output in racing form. I would at least expect 2hp per cu.in., if not more. Have I lost my grip on reality here? I'm just surprised... Maby too many limitations on modifications as opposed to just cubic (dollars) inches...

What I was expecting to hear, was horse power level differences, say between a Mark75, and an OMC, both running FEH. I know which one sounds sweeter.....

The same differences in other classes as well....

I have a long way to go, and such a short time to get there.........trader......

[Mark75H]

In FE we have some nice equalizing rules.

First we are restricted to gasoline for fuel. The MacMinerelli runs in PRO where you can run alcohol.

The 3 cylinder OMC's have to run carbs they came with. The rule says "that motor's service carburators"

The 6 cylinder Mk75 Mercs use the ancient "deflector" piston/porting/cylinder head.

These two things stop us pretty tight at a little over 80 hp in FE.

Back in 1960 Burt Ross set a record with a 60ci 6 cylinder Merc at 115 mph. I think that motor was 90 hp or so on alcohol and nitromethane. We just know that because the OMC guys got ahold of one just like it to dyno and figure out how much power they would need to increase the record (they did, to 122 mph). I think their motor was about 105 hp, but it ran on pump gas at 5,500 rpm or so and was 89ci.

In PRO we might be able to track the power increases along the claims from Dieter König in the late 50's and early 60's, but it isn't like he bought ads in major magazines each year. I haven't even came across as much as a flier with hp claims after about 1962.

In the stock classes we take what we get only hoping for motors equal to what has been existing in each class to keep the speeds the same. There were a lot of bad feelings when the KG7's were obsoleted by the Mk20H's. Another wave came thru when you had to convert your Mk20H to the Tillotson and toilet bowl around 1960 in order to stay competitive.

[Oclassracer]

I believe hp is usually a direct link to how effiecient the "pump" is. The Mac has a bore of 56mm and a 39mm carburetor, so I think it moves a lot of air..fast. Before producing powerheads for international "O classes" they produced engines for karting. I believe the dyno sheet to be true, but you never know....engine builders may be a little prone to a story, but I would think it has to be within 5 hp.

Sam, I have a 1975 Konig 125 we can compare it to. It should produce about 25hp

[TRADER]

OClass, I don't dispute your declaration. I agree that engine builders, can embellish on the figures somewhat, as they try to "dyno" in the most ideal of circumstances. It is designed to give a baseline, to adjust from, under different field conditions. For that, I feel they are invaluable, to the tuner. They are also the best tool for checking for losses or gains, for changes, made against a baseline configuration. None the less, there is still a "big dick" ego, associated with the results...that is both difficult to confirm/dispute...

At the time I talked to Striker (1989-90), he told me, they were getting somewhere between 4.25 to 4.5hp per cu.in., 16.00:1 compression, 120 octane fuel, at around 10,000rpms. He calculated about 30hp @ rear sproket. He was so closely associated with Earl Gearte, in Indiana, and like I said, very modest about his abilities/skills...

Sam, about the only inequality I viewed between the OMC's and a single MK75, at a race in Trinity Tx, this past spring, was the obvious dynamics involved in the turns. High roll center, and yes, it did roll!...trader...

[Mark75H]

The 6 you are most likely to see in Texas belongs to Cleaburn Phelps and is one of the original factory Mark75H's.

One thing we are allowed to do in Mod is make custom short mid sections. Mr Phelps' Mark75H is only 1/2" shorter than a 55H; basically made for a 15" transom. I use a 6 1/2" mid exactly half as tall as a 55H type mid on my 9" transom. On top of that I set mine up (with help from Dave S) to be 1 1/2" shorter above the swivel pin as well. This brings my powerhead to 8 inches shorter than if I used a regular 55H type mid. It corners like it's on rails and I can easily and safely increase or decrease the radius of a turn in mid turn under full throttle.

An OMC triple block and base adapter are 17" tall, my block is 19" tall and sits right on the tower. An OMC has to be on a 8 1/2" tower to be as short as mine is.

My 6 1/2" mid is not the shortest I have ever seen on a 6 . . . Bill Fales had one that was only 4" tall back in the 60's.

[TRADER]

I was a guest at his trailer that day. I believe that it was a 1 mile course. His regular driver, Earl Mitchell, was there, but not as a driver. He had what they thought was a stroke, sometime earlier, and was now a spectator, with the rest of his family. He died later this summer of Parkingston's disease. Had been misdiagnoised? Any way Cleburn's son in law, Chuck Doane, took the seat for the very first time in Phelp's hydro. He has experience in/own's a lay down SEH, W/3/OMC, and was nervous about not having any time in this rig. (daddy in law you know) He does an outstanding job, non the less, coming from behind, to pass all but the lead boat, and got caught in some back washer's mistake, and fliped/rolled. We laughed, that he wouldn't have to wonder what that felt like anymore. A very fast, hard hitting, sweet sounding rig.

It was heartwarming to watch Earl, driving in proxie, from his chair on shore, as his wife chanted, " Listen to your baby sing, Daddy"..............

Cleburn had two boat's there. A Pughe 12'+ FEH and a DeSilva runabout. Had Mark 75's on both, and a spare powerhead. The Pughe had a shorter (than 15") transom, and I believe Albert said it had a 38" bottom, to handle the extra weight of the motor. Both Mark 75's, had Sid Bass towers, the FEH being a 8" unit. I'm not sure about the one for the runabout, and both had Sid Bass gear cases.

Perhap's he has upgraded, since you last saw... That was the first, and only, outboard race I have attended... I met a lot of fine people there, and carried away some fond memories....trader

[Mark75H]

Yeah, I have one of the boats (a 12' DeSilva tunnel hull) they considered before Phelps had the wide Pugh built. The boat I usually run is a std Pugh 350 alky hydro 36" wide. More than wide enough with a short tower and big enough turn fin. Going to a 6 X 6 fin and dialing in the angle made as much difference as the short tower . . . but both are neccessary. "Farmer" John Runne is building 2 wide boats for FEH this winter . . . I don't know how wide, but he keeps building them wider and wider . . . I guess he will find the limit after while.

They must have moved the 75H foot to back up status when it got a crack in it a couple years back (it's been fixed since). I think they ran it every season for 42 years before it cracked.

I wasn't aware Bass made a tower that short, I thought his were all std height.

Sorry to hear Earl passed away.:(

[David_L6]

The drawing of the Bass tower that I have gives a measurement of 8.5" from top to bottom of tower. This isn't counting powerhead and lower unit adapter plates; those will add ~1".

[MODIFIEDOUTBOARD]

Here we go again.

Modern "production" high performance two-strokes are now making well over 2hp/ci on pump gas. Production watercraft engines are an example. No they are not "peaky" but make 2hp/ci at 7,000 rpm or so and still make more power than outboards(of the same displacement) do every where in their rpm range.

If you can accept the above than it would not be hard to understand that a "properly" modified Looper like 45ci OMC twin will easily make 90hp@7,000rpm or an all out 49.7ci OMC triple "properly" modified will make over 100 hp with the carbs it came with.

A prevelent approach to making a mod outboard race engine that I see after talking to racers is try one thing at a time and if does not do improve performance do not try it ever again on anything else. Many of the mods that I have found beificial are said not to help "cause I tried it" .

Example: (Raising compression on a 45 ) The majority of the 45's I have seen do not have high compression and the people I have talked to said "it does not work". They do not under stand why it slowed their boat down. On the 45 with the chamber a racer put a stock powerhead w/High comp head on a mid-section with the chamber and picked up 600 rpms on the stock test wheel and the 13' Sorenson finally lifted coming out of the turn instead of at the end of the straight. Later in the summer the same racer ran a mod powerhead on the same tower and saw 8,000rpm on the stock test wheel. He beat the triple next day at the races.

Cross flows are a different story and the technoligy has been well developed by racers over the years. Do not see them going much faster on gasoline in the future.