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Thread: Crescent 500 specs

  1. #21
    modifiedoutboard OUTBOARDER's Avatar
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    Default cresent port specs

    Quote Originally Posted by Frank Volker View Post
    I recall a C-Hydro race at St Joseph, MO (1966/67 ?) in which Bill Seebold was driving a Crescent. It sounded like it was having fuel problems, but about 1/2 way through the race it cleaned out and looked like it had 5 mph and a ton of acceleration on everyone. I don't recall where he finished or if he finished at all, but when it was running it was in a class by itself.

    Here's what I recall about the alky Crescent:
    1. Pure piston-port intake with no reeds.
    2. Central combustion chamber.
    3. Slightly domed pistons. One ring(?).
    4. The compression was very high.
    5. The bottom exhaust passage was angled upstream slightly.
    6. The exhaust inside the housing was a straight pipe and short (6" or so) megaphone.
    7. The entire engine assembly with housing and lower unit was very light.
    8. The cylinder walls were chrome plated (I think).

    Overall, I thought it was a very impressive engine, but then I've always been a fan of 3-cylinder engines. The only possible show stopper for me would be the chromed cylinders.

    Frank

    anyone know actual Port Specs ????
    ANTHONY McCULLOCH
    modifiedoutboard@hotmail.com

    Some things never change!

    They Want it cheap..............

  2. #22
    Sam Cullis Mark75H's Avatar
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    Quote Originally Posted by Per View Post
    Nope, AFAIK there are no relationship between the SAAB and Crescent engine. I will speak to a couple of knowledgeable people and see what I come up with...
    Per is correct, there is no direct relationship. In truth, they are radically different motors, only sharing the 3 cylinder inline, 2 stroke commonality
    Since 1925, about 150 different racing outboards have been made.


  3. #23
    Sam Cullis Mark75H's Avatar
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    Here are the NOA specs of the Crescent Alky

    If you are looking for a port map with the widths and contours, you will probably have to purchase a motor and disassemble it.
    Attached Images Attached Images  
    Since 1925, about 150 different racing outboards have been made.


  4. #24
    Sam Cullis Mark75H's Avatar
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    Quote Originally Posted by Frank Volker View Post
    I recall a C-Hydro race at St Joseph, MO (1966/67 ?) in which Bill Seebold was driving a Crescent. It sounded like it was having fuel problems, but about 1/2 way through the race it cleaned out and looked like it had 5 mph and a ton of acceleration on everyone. I don't recall where he finished or if he finished at all, but when it was running it was in a class by itself.

    Here's what I recall about the alky Crescent:
    1. Pure piston-port intake with no reeds.
    2. Central combustion chamber.
    3. Slightly domed pistons. One ring(?).
    4. The compression was very high.
    5. The bottom exhaust passage was angled upstream slightly.
    6. The exhaust inside the housing was a straight pipe and short (6" or so) megaphone.
    7. The entire engine assembly with housing and lower unit was very light.
    8. The cylinder walls were chrome plated (I think).

    Overall, I thought it was a very impressive engine, but then I've always been a fan of 3-cylinder engines. The only possible show stopper for me would be the chromed cylinders.

    Frank
    Frank is correct, piston port intake with a rear wall transfer port complementing the side transfers. The cylinders were chrome directly on aluminum, so they were not repairable in that era.

    There was no interchangeable tuner.

    It was not related to the Archimedes Monark triples either.

    The reason it was abandoned was the cylinder spacing was so tight there was no room to alter the porting or make any other changes to the design ... the power had been surpassed by the 1966/67 Konig VC design motor and was obsolete without a complete redesign from the ground up. The cylinders lay together slightly tilted so the port passages of the center cylinder interlay between those of the top and bottom cylinders. Tight, compact, light and - stuck as a design build.
    Since 1925, about 150 different racing outboards have been made.


  5. #25
    Sam Cullis Mark75H's Avatar
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    Had to look thru a couple hundred pages of archives ... rpm range around 8,000
    Since 1925, about 150 different racing outboards have been made.


  6. #26
    modifiedoutboard OUTBOARDER's Avatar
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    Quote Originally Posted by Mark75H View Post
    Here are the NOA specs of the Crescent Alky

    If you are looking for a port map with the widths and contours, you will probably have to purchase a motor and disassemble it.
    these numbers make sense, exh opens at about 87 deg atdc and trans at about 114 deg atdc (like omc 49)
    thx Sam
    ANTHONY McCULLOCH
    modifiedoutboard@hotmail.com

    Some things never change!

    They Want it cheap..............

  7. #27
    Team Member BRIAN HENDRICK's Avatar
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    Quote Originally Posted by seacow View Post
    "The Crescent was built by Monarch Crescent, they also built bicycles and mopeds. Some of the same engineers may have been consulted. Most of the powerhead main components were made in Germany. M.C. was later purchased by Volvo Penta.
    -Dick O'Dea"


    No more to add to the info re: the 500cc o/b, but I did own a MONARK motorcycle for a time back in the late 50s.
    It was a 350cc 2 cylinder, 2 cycle, 3rd port motor.
    For that era, it was ahead of the Brit bikes.
    Also this brochure on a MONARK 250cc twin . Note this motor is a JLO.
    a well known German maker of 2 strokes.
    All to say they were well capable of producing a 3 cyl o/b.

    Name:  Monark 250.jpg
Views: 497
Size:  140.7 KBName:  MONARK BH.jpg
Views: 410
Size:  68.3 KB

  8. #28
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    Default Changeable tuners

    Quote Originally Posted by Mark75H View Post
    Frank is correct, piston port intake with a rear wall transfer port complementing the side transfers. The cylinders were chrome directly on aluminum, so they were not repairable in that era.

    There was no interchangeable tuner.

    It was not related to the Archimedes Monark triples either.

    The reason it was abandoned was the cylinder spacing was so tight there was no room to alter the porting or make any other changes to the design ... the power had been surpassed by the 1966/67 Konig VC design motor and was obsolete without a complete redesign from the ground up. The cylinders lay together slightly tilted so the port passages of the center cylinder interlay between those of the top and bottom cylinders. Tight, compact, light and - stuck as a design build.
    Might better double check that info about the tuner.......It did have two different length internal pipes. One was for long run coarse and one for short. They were easily changed out according to historian and collector, Mark Suter. This engine was very similar to the Archimedes 45 hp and was actually close in horsepower output. The Cresent was likely the same as any other manufactured race outboard as to be derived from an existing domestic version engine with only few changes and castings. It is doubtful to me as a former machinist, that a production company would tool up just to make one special race engine totally separate from any other components they make for other use, in such little quantity. It is likely that with a little research, one could interchange some parts to build a Cresent engine from an Archimedes or Volvo the same as a Sweet 16 champion can be used to build a 6MMHR hotrod... or.....a Merc200-250 to make a 25SS. There's probably nothing outstanding to it at all. This engine could probably be built as a COPO. That could be a good idea to possibly consider, building a good historical race engine for anyone who would like to have one of these.

  9. #29
    Sam Cullis Mark75H's Avatar
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    Doubtful or not they did. It is a unique project. Unlike OMC, Mercury and Champion, they did not build the C off of any of their production parts.

    If you read Swedish and German there is a bounty of documentation of the development of the project. The tuner was not an option thing, like the super long nose cone on the record motor, it was a one off piece. Probably only 1 or 2 made, its not like you could order one - more like the factory made ONE for themselves to use. I don't consider that a regularly available part to say "They made this and that and the other." Do you follow me? Its like the Merc dual torpedo SuperSpeedmaster unit.

    There is a guy in England building such a replica, but it is very different from a true Crescent C racer; essentially NO C racer parts are on his replica other than the orange paint.

    No COPO here.
    Last edited by Mark75H; 06-09-2014 at 06:39 PM.
    Since 1925, about 150 different racing outboards have been made.


  10. #30
    Team Member BRIAN HENDRICK's Avatar
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    Quote Originally Posted by Mark75H View Post
    ,,No COPO here.
    OK, I will bite, what is a COPO ?

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