Mazda Powered Inboard

[Tomtall]

This boat is posted on E-Bay. Does any of our Inboard historians know anything about this hull?

Can read about it at http://cgi.ebay.com/Vintage-Hydroplane-Boat-Engine-Complete-Workshop-NR_W0QQitemZ230029942389QQihZ013QQcategoryZ423QQrd Z1QQcmdZViewItem

[Tomtall]

http://contact.ebay.com/ws/eBayISAPI.dll?ShowAllQuestions&requested=jlayne13&iid=230029942389&frm=284&redirect=0&ShowASQAlways=1&SSPageName=PageAskSellerQuestion_VI

[John Howe]

There was some discussion about this boat over on the vintage hydroplane website earlier this week. I`m pretty certain that the rotary Mazda motor was not legal for that class, so I think that the rotary concept was an experiment by the owner.

[David Weaver]

There was some discussion about this boat over on the vintage hydroplane website earlier this week. I`m pretty certain that the rotary Mazda motor was not legal for that class, so I think that the rotary concept was an experiment by the owner.

There were some engines pulled from RX-7's used in this class. Would these have been rotary valves? I also remember a Porsche engine and some Datsuns. A great calsss then and I assume now.

[John Howe]

Years ago I worked with a guy that had a Mazada, with a rotary, and he took me for a drive in it. That little car could move! I do remember some discussion about allowing the rotary motor, but I understand that there was negative feed back from inspectors, and competitpors, because they were so un-familiar on how to inspect it. It seems that the "A" class inboards (modified 2.5 litre) are struggling now due to the high cost of a competitive motor. Some of the "top dogs" in the class are using engines designed strictly for racing. I`ve heard it mentioned that Larry Lauterbach`s 2.5 engine, made by Eslinger Engines, costs in excess of $40,000. In Hampton this year there were 6 "A" boats in the pits. After 4 heats of racing, only 2 remained running, with one of the two really struggling.

Here`s a link to the basic concept of how a rotary engine works.

http://www.keveney.com/Wankel.html

I can understand why inspectors, and competitors, might have been "cool" on the rotary idea back then.

[John Howe]

Yeah, I understand that they do run rotary/Mazda motors in a few drag classes. However, it`s in bracket drag racing classes, which is not full "heads up" racing. By "heads up" I mean the first one to the finish line wins. In bracket racing you tell the officials the time your going to run, but if you get the finish line to quick, your eliminated.

[will350]

There was some discussion about this boat over on the vintage hydroplane website earlier this week. I`m pretty certain that the rotary Mazda motor was not legal for that class, so I think that the rotary concept was an experiment by the owner.

I doubt that rotary Mazdas were ever a "legal" motor in inboards.
They came in 3 sizes,60ci(10a),70ci(12a)and 80ci(13b). the difference between them was length,The 12a was 5/8" longer than the 10a,the 13b was 5/8" longer than the 12a. They can make huge HP for the displacement depending on the modifications(mostly porting,intake-exhaust)and they'll turn up to scary rpm(a 10a would go to 12 and live,15 if you didn't mind replacing it every 6 months or so) A 12a would do 10-11,a 13b would run 9-10 with a "reasonable" TBO for those kinds of rpm. They make a tremendous amount of exhaust heat(I had one that would turn the headers red to 3' behind the motor.I could see it becuase there wasn't a boot for the shift stick).They are INCREDIBLY LOUD when unmuffled and there is enough unburned fuel that a short stack setup resembles an F-14 on afterburner.One of the folks that used to be around here made a "hot saw"(2 man chain saw) out of one.It would go through a 36" log in 3 seconds + or - a few hundredths and shoot a 4' flame out the stack.I've heard accounts of having the headers break on the front stretch at Pacific Raceway and the driver going temporarily blind because the noise does such a number on the auditory nerve.
The lates ones are injected with an intercooled turbo.One of my friends has an RX3 with that setup in it that he runs in SCCA.Scary fast.
Will

[John Howe]

Hey Will350, thanks for your input, ...good read. I`ve wondered from time to time about the rotary motor. After I went that ride, somewhere back in the mid 80`s, my buddy opened the hood and I was surprised by: 1) the small size of the motor, and; 2) the large 4 barrel carb on to top of the intake. I understand, at least back then, that they had emission control (pollution) problems and that the rotor seals didn`t last long. Still, I understand why it would attract racer types, being small and thus light weight,...and very powerful.

[Sunburnt]

Here is a link to a couple of videos of a twin Turbo Rotary Water Ski Race Boat. Very cool stuff. They are from Australia..

1962cc, 800Hp @ 9500RPM. WOW!

http://www.xtremerotaries.com.

http://www.xtremerotaries.com/main2/Quicksilver/60-102mph.wmv watch for the ending..

http://www.xtremerotaries.com/main2/Quicksilver/In%20boat%20footage.wmv


Jeff

[will350]

Hey Will350, thanks for your input, ...good read. I`ve wondered from time to time about the rotary motor. After I went that ride, somewhere back in the mid 80`s, my buddy opened the hood and I was surprised by: 1) the small size of the motor, and; 2) the large 4 barrel carb on to top of the intake. I understand, at least back then, that they had emission control (pollution) problems and that the rotor seals didn`t last long. Still, I understand why it would attract racer types, being small and thus light weight,...and very powerful.

These use a LOT of air per turn.A 13b will pull the same amount as a 327.
The one I had was "bridge ported" 12a(70ci) in an R100.The motor came out of a CMC(C modified compact) that ran in the high 12s with a 750 Holley in an RX3.The R100 was about the same size and weight as a VW bug.At 55mph(2500 or so rpm),it got about 20mpg.At 4500rpm it would get 27mpg but there weren't many places where you could rocket along at at 90mph without some attention from the constabulary.
The emission issues were all about the "idea" that the ci rating was so small that they "couldn't" produce the emissions they did.They use twice as much air per revolution as they're ci displacement VS a "normal" piston engine(a 260 V8=130ci of intake per 1 revolution,a 70ci rotary=140ci of intake per revolution)so from an emission stand point,I think it was difficult for the "emission folks "to understand.
The seal issues were mainly due to running them really hard when they were cold or overheating. They're bolted together from end to end at 25lbs or so,torque wise.If you ran them hard cold,the rotor housing would "vibrate"
and if you overheated them,you got the same effect,the seal would go south in the combustion area on the rotor housing.Tip(apex)seals weren't much of a problem until many,many hours of thrashing the fool out of them.
I had wads of "fun" with my little unit.Shifting into 4th gear as you passed a big block anything at 115-120 was always good for a look of "what the .....".
Will

[Master Oil Racing Team]

What put the big hurt on the rotaries was mine and Skoontz' most favorite and thoughtful agencies:rolleyes: ---the EPA. After the first gas shortage in 1973 and after EPA was first formed, they decided to test cars and post milage figures. They did all of this on a treadmill, with about a 20 minute or so run. They measured an exact amount of gasoline before and after the run as well as tailpipe emissions to measure the amount of unburnt fuel that passed through. The treadmill was designed as a stop and start trip on the way to a store and maybe a little highway driving---say 45 mph. From this they calculated what the fuel milages were.

The Mazda rotary valve engine was 15 or more years ahead of the pollution standards of the time. As Will 350 stated, the exhaust was very hot. This was because the motor was designed to incinerate pollutants. It did this by pumping small amounts of fuel into a thermal reactor that heats up to 1600 degrees F. You don't want to park a Mazda in a field of tall grass with the motor running.;) And that's what threw the EPA figures off. Until the motor is warmed up, that excess fuel was picked up by the monitors. It takes 3 to 4 minutes for the thermal reactor to be at its operating temperature. So there is a huge amount of fuel compared to 4 cycle engines coming out the tailpipe for 20 to 25% of the test, thus giving a false result as compared to actual milages that could be achieved.

So did any of these supersmart know-it-all Captain Planets and their superiors ever actually drive one? Or ask somebody who did? Or believe the manufacturer? No....if they say it....it has to be true. So according to the EPA a rotary valve got 10-11 mpg. My RX2 got 18 to 22 mph depending on how hard I ran it. And it would do it with the cheapest gas around. The Toyotas and Datsuns of the day had to run on the most expensive--Premium. When those figures were published, it almost killed the company, they did struggle back and later made the RX7, but the rotary never gained back the momentum.

[Jeff Akers]

My firts car was a 1973 Mazda rx3 coupe:D ....If I remember corectly, my grandad bought it new in 73...drove it to church and back on sunday;) ..some time after that they had a factory recall...they replaced the entire engine for some reson:confused: ...it was then given to my dad..who then past it on to me in about 1980?...
I had a blast with that little car.It would eat up any other car of it's size in the 1/4 mile...and on the twisties:eek: The thing was unbeleivable.....
Just reading this thread makes me :) ....I hated to get rid of it but...I traded it in for a Datsun pickup to hall my dirtbike in:D

Edit: Sorry for the (off boat topic) . couldn't help it.

[Master Oil Racing Team]

....the engine was a rotary;) When I went to Africa in 1975, I left my Mazda at the man's house I was going to see. His kids raced everyone within a three block area and won. After I got back, I had a water leak from the water jacket into the rotar chamber. It had 90,000 miles on it. I went to overhaul it and I took these pics two weeks before I stuffed my hydro on Memorial Day. I had the block all back together right before the race, but after my crash, it was a year before I could get back on it. In the meantime, it gummed up inside so I had to tear it down and clean the parts back up before I put it together.

[John Howe]

Thanks for posting the pics, Master Oil. Also, thanks Sunburnt for providing the web links. I think it would be cool if the rotary could find it`s way into inboard boat racing!

[Master Oil Racing Team]

Thanks John. And as to your question on the longevity of the rotor seals, I miked (?mic'd? I know it's can't be miced:D )the apex seals of mine at 90,000 miles and projected they had another 20 to 30 thousand miles of life left. There are also two bands of seals kind of like a section of piston rings on the side of each of the triangular lobe on both sides, and a small cylindrical seal with a keyway cut for the apex seal that fits in each tip of the rotor.

The key for long life of a rotary is to let it warm up before you get on it. The basis motor is a cast iron cap on each end with a cast iron section in the middle and aluminum rotary housings sandwiched in between. Unlike a reciprocating engine (as the moving illustration shows) the intake, compression, firing and exhaust takes place in a different spot rather than in the same cylinder. When you just fire up a rotary and get on the power hard, that exhaust section of the aluminum rotary housing will really start to expand and move. The cast iron will take longer. The intake sections will not stabilize until the coolant has circulated enough to warm that section up.

When the aluminum is heated up so rapidly, it expands outward against both sides of the cast iron, and across the cast iron. That will break the seal of the water jacket and you will get water in the rotor housing. I drove mine that way for several thousand miles before I got the parts in. Fortunately, the spark plugs were easy to get to. If I was parked longer than 30 minutes, I had to pull the plugs, crank the engine over to pump the water out, then put the plugs back in and be on my way. Takes only a few minutes. You notice there are two spark plugs per rotor chamber.

The close up is the section near the exhaust port of the rotor housing where the leak occurred on both of my rotor housings. I'm guessing that this is where all or most of the failures are.

[Skoontz]

OMC ran a 20" wide track snowmobile in the early 70's that was rotary powered we called "The Hog"

Cool thing about it was the smooth flow of power from even the lowest RPM, and for the sleds of the day, there were no 20" tracks that could hit 60, let alone the 70 that the Hogs would run. Out of the hole that 20" of belt grabbed hard and there was no power band to deal with that the 2 stroke engines of the day used.

I always wanted to run a rotary engine in a Go Cart, but could never find a trashed Hog to yank one out. For a small inboard engine, that would have been great, but I could see where an air cooled rotor would heat up fast in hot weather.