Please be advised that we have been requested to vacate the premises from the end of March 2020, with the last race meeting being 7 March 2020.

  • La Farge Mining SA (LMSA) have a huge mining contract and will be mining in the quarry from the end of March.

  • Please be advised that on the instruction of LMSA no-one will be allowed on the property after the 7 March.

  • Anyone entering or trying to enter will be dealt with by the security company and LMSA.

  • CMBC cannot and will not be held liable for anyone attempting to enter and disregarding our communication.

  • We trust that we will find temporary premises to accommodate us for this period of time.

Section 2

Classes and Class Registration

Classes by engine type and capacity

  • F1

    • 3.5 Nitro - Maximum engine capacity: 3.5cc (Nitro)

    • 7.5 Nitro - Maximum engine capacity: 7.5cc (Nitro)

    • Gas Outboard & Inboard - Maximum engine capacity: 35.0cc (Spark ignition)


  • Offshore Modified engines

    • Offshore Sport - Maximum engine capacity: 4.2cc (Nitro)

    • Gas offshore Mono - Maximum engine capacity: 35.0cc (Spark ignition)

    • Gas offshore Catamaran - Maximum engine capacity: 35.0cc (Spark ignition)

    • Gas Inboard & Outboard Tunnels - Maximum engine capacity: 35.0cc (Spark ignition)


  • Gas offshore Stock (Unmodified) engines

    • Stock Mono - Only this one engine / capacity: 25.4cc Zenoah G260 PUM

    • Stock Catamaran - Only this one engine / capacity: 25.4cc Zenoah G260 PUM


  • Hydroplane/Outrigger modified engine classes

    • 3.5cc Nitro - Maximum engine capacity: 3.5cc (Nitro)

    • Gas - Maximum engine capacity: 35.0cc (Spark ignition)


NOTE ! All mono, catamaran and F1 boats must have a robust carrying handle/s to facilitate launching and lifting of the boat from the water by the rescue-boat crew.


Class Registration

  • There is no requirement to ‘register’ any of the seven current classes below. However starting up any other class would require a request to, and approval by, the club committee.

  • Classes currently being raced at CMBC are as follows

    • Formula-1 Gas Inboard (Modified spark-ignition engines, 35 cc Max.)

    • Formula-1 Nitro Outboard (Modified engines, 7.5cc Max.)

    • Offshore Gas STOCK Mono or Catamaran hulls. (Stock spark-ignition Zenoah G260PUM 25.4cc)

    • Offshore Gas MODIFIED Mono or Catamaran hulls. (Modified spark-ignition engines, 35cc Max.)

    • Gas Sport-Hydro/Rigger (Modified spark-ignition engines, 35cc Max.)


  • Classes that were previously raced at CMBC but have not been raced for at least the last season are:

    • Formula-1 Gas Outboard (Modified spark-ignition engines, 35cc Max.)

    • Formula-1 Nitro Outboard (Modified engines, 3.5cc Max.)

    • Offshore-Sport Nitro Mono or Catamaran (Modified engines, 4.2cc Max.)

    • Nitro Sport-Hydro/Rigger (Modified engines, 3.5cc Max.)

Gas Stock Class Engine Specification Rules

  • In general, the following rules apply: (Some exceptions follow below)

    • This class shall only use the Zenoah G260PUM motor and no other.

    • The motor must remain stock as is supplied by the manufacturer and may not be modified in any way. No component material may be removed or added in any way.

    • All parts on the motor must be as supplied by the Zenoah Company.


  • Carburetion exceptions

    • Only the Walbro 644 and 257 carbs may be used. These may have the choke butterfly removed (644) and bolt-on velocity stack removed. No other modifications may be made to the internals and flow path of the carburetor.

    • NOTE! ‘Butterfly’/shaft units of the above carburetors may be replaced with aftermarket parts of exactly the same shape and dimensions as the original part.


  • Base gasket

    • Only the blue base gasket as supplied by Zenoah may be used. No aftermarket (compression enhancing) gaskets may be fitted.


  • Piston

    • Piston shall be the manufacturer supplied piston only. No lightening or relieving of piston is allowed.


  • Ignition Coil exceptions

    • The grey ignition coil may be relocated at the pilot’s discretion.

    • The following aftermarket coils may be used in place of the original coils. Details may be obtained from the committee.

    • (See photos below of the two aftermarket coils that are permitted!)


  • Bearings

    • Any off the shelf, metal cage 6001 bearing maybe used with the necessary chamfering done to it to ensure the needed crank float.

    • No fiber cage bearings with ceramic balls will be allowed.

    • No metal cage bearings with ceramic bearings will be allowed.


  • Seals

    • OEM Zenoah seals, as well as locally available aftermarket seals may be fitted. Seal retaining springs may not be removed.

    • No aftermarket zero drag (Metal) seals may be fitted.


  • Spark Plug

    • Spark plug may be replaced by an NGK of the same specifications as the Champion supplied with motor. No Iridium plugs allowed.


  • Pull Starter

    • The original pull start unit may be replaced with a OE easy start or an aftermarket easy start/pull start unit.

    • Addition of a ‘Geezer Wheel’ behind the collet chuck is permitted but a complete pull start unit must remain in place and be in working order. Boats may be started with the rope pull start, or with a belt on the ‘Geezer Wheel’ using an electric starter.


  • Exhaust/Tune Pipe System

    • Header Tube:

      • A header with OD (outside diameter) of no more or less than 22mm or 7/8” (22.23mm) must be used. This header diameter must run all the way until the start of the diversion cone. No progressive (increasing diameter) headers or integrated headers would be allowed. For clarity, this eliminates the legal use of a Quickdraw header as its diameter increases towards the rear.

      • See definitions from the English dictionary of the words ‘PROGRESSIVE’ and ‘INTEGRATED’ below.

PROGRESSIVE (Adjective):

Favoring or advocating progress, change, improvement, or reform, as opposed to wishing to maintain things as they are

INTEGRATED (Adjective):

Combining or coordinating separate elements so as to provide an interrelated whole

    • Tuned Pipe

      • The tuned pipe may be any available pipe (commercially or custom made) but may not have more than 2 diversion cones and 1 conversion cone. Any parallel band width (fattest part of pipe) pipe may be used. All pipes must be muffled to meet the 95dB limit set as per the noise regulation.


  • Scrutinizing

    • Race control is entitled to decide on an engine scrutiny of any stock class participant’s boat at the end of any race day. Such scrutiny will be carried out in the presence of race control, and 2 other members appointed by the committee.

    • At this motor inspection the club would supply a new blue base gasket to replace the one on the scrutinized motor if the member request it. If at any time the scrutiny officials decide that an engine has been modified, the member would lose all his/her points for the season to that date. On the second offence by such a member, he would be brought before the committee where he may be suspended from the club indefinitely. (i.e., membership terminated!)