Facts about Evinrude/Johnson racing outboards made my OMC

[Lake X Kid]

The fuel tanks in the boats were the same as the V-4's and V-6's. You must remember, fuel consumption is related to HP (among other things). Thus a 300 HP rotary would use more fuel that a 175HP V-4 if they had the same efficiency. However the rotary race engine was twice as fuel efficient as the V-4/6 when measured as BSFC; .68/.75 for a 2-stroke vs .35/38 for the rotary lbs. of fuel per HP- Hr.

The Rotary might be more fuel efficient than the V-4/6 engines, but didn't the Rotary spew out more oil and unburnt fuel out the exhaust chambers?

I recall reading were one of the race drivers didn't like trailing behind the OMC Rotary because of the exhaust plume.

[Rotary John]

The Rotary might be more fuel efficient than the V-4/6 engines, but didn't the Rotary spew out more oil and unburnt fuel out the exhaust chambers?

I recall reading were one of the race drivers didn't like trailing behind the OMC Rotary because of the exhaust plume.

You're an engineer. You should realize with a BSFC in the high to mid .3's, there isn't much excess coming out of the exhaust; especially compared to a 2-stroke. Add to that an exhaust temperature in excess of 1800 oF, most of the excess is burned up before it exits.
A secret about the rotary race engine I've never disclosed before, is there was a SS baffle a specific distance from the end of the exhaust tubes that reflected a positive pulse back up the tubes. This was the tuning feature that allowed for the diesel level BSFC. That baffle was only cooled by splash water injected into the horn after the baffle. What was coming out of the exhaust relief tubes was STEAM.

I suspect other drivers didn’t enjoy being stuck behind the rotary, since they kept getting passed again.

[Rotary John]

Great song...Choosing Texas with Ella Langley.



While Abilene, Texas, isn't a major powerboat racing hub, it has connections to boat racing history, especially through

Abilene Marine, a company that sponsored Formula 1 tunnel hull racers using Johnson Outboards in the 1980s, with drivers like Johnny Sanders and Tom Posey, featuring prominent teams that competed nationally. So, "Johnson Boat Racing" in Abilene links back to these specific teams from decades ago, rather than a current major scene.

That's Posey with the balding head. Alan Yaw was the power behind that team

[lars strom]

Pit crew for Tommy at this race was Jerry Gravesen (left) and Sam LaBanco (right), both of which have been APBA National Champions.

"Thanks for info my friend"

[Rotary John]

OMC Rotary Race Engine
I reflect back now; some 50+ yrs. later; on what I would have down differently to improve the engine durability and performance. The two major issues affecting durability were the thru bolt breakage and rotor bearing failure. We also saw an occasional premature apex seal wear. We had solved the broken thru bolt issue with the 4 pc. crank design. I had developed apex seal materials that showed no measurable wear after 100 hrs. continuous WOT. in addition, they cost less the $.05 each. A fraction of the cost of the Torrington supplied seals. I still have one in my desk drawer. The rotor bearing was always a potential problem. The engines were adjusted a rich as possible before losing HP and was run at 20:1 mix ratio. I had developed a unit cage design with INA bearing that consistently ran 100 Hrs. on the Snowmobile engine test cycle w/o failure. Never got a chance to run them in a race engine. Another significant improvement would have to add oil injection thru the crank. Rotor bearing failure was a result of heat generated between the cage and the outer race due to lubrication breakdown. According to SKF Research, failed bearings demonstrated outer race temps in excess or 1800 F. This was far in excess of the 458 F tempering temperature causing the race to shrink to the point is would seize on the crack and all hell broke loose. The failure always started on the downstream side of the bearing due the "C" section design's ability to get sufficient oil in that interface. Direct oil injection thru the crank along with the unit cage bearing design would have eliminated durability. problem #2.
Several areas to improve performance were on the list but never got fully explored. Titanium rotors would have reduce the rotor weight by about 50%; around 20 lbs. for all 4 allowing higher speeds w/o increased loads. The increase in Hp between 7000-9000 was in excess of 40HP. Titanium also has several thermal properties that are advantages over cast iron. I knew the rotor combustion pocket design had potential to affect power, fuel consumption and emissions. Previous development testing had shown an 8% power increase when a trailing spark plug was added; upping power 20/25 HP. Adding the trailing plug caused thermal cracking on the rotor housing and was never run on the race engine. We had just started to explore alcohol. Alcohol would lower the air temp going thru the rotor, improving the engine specific air consumption and helping the bearing issue.
Overall, my vision for the future of the race engine was 400HP at 9000RPM. When the 2L issue was being raised to run ON, I was all set to grind off a little on the housing and the rotor. OZ suddenly came back into vogue, so it became a mute issue. The last year of the program I was the only engineer working on the race engine with a part time designer so my too due list was overshadowed by fix the problem from the last race so we could go to the next race.
Strang had achieved his objective of beating Merc and was pushing V-6 development hard. He felt with 150 CI V-6 he could continue to do battle with the 2L Merc, so the rotary programs were but on the back burner and I was assigned various 2-stroke projects.