Box Design

We hope to make this one of the most interesting features of the web site, here we attempt to show our guests the design process for a cracker box boat. from design to finish we will attempt to break down our intricate and complex boats. Information about the design of the boat will be added soon!


50.1 Crackerbox class boats must measure in accordance with the specifications and limitations set out in these rules and in the official drawings which may be obtained from the American Power Boat Association, National Headquarters.

50.2 The total maximum displacement of motors used shall not exceed 275cu. in. There shall be no tolerance about this figure.

50.3 Competing boats shall be powered with one internal combustion motor of four-cycle type. Carburetors or fuel injection shall be permitted. Motors shall be equipped with an efficient starter. The ignition may be battery or magneto. The block must originate from an engine of cast iron, designed and built by a U.S. automobile manufacturer for use in passenger cars and trucks. The cylinder heads must be of OEM design, but after market parts may be used including aluminum heads. There shall not be more than two valves per cylinder.

50.4 There shall be no superchargers or overhead cams.

50.5 Alternate motor- Not to exceed 314 cu. in. Shall be limited to one 650 CFM Holley carburetor Model #4150, Part #4777, and all dash numbers; this carburetor is to remain as furnished by manufacturer. Any modification not written herein will not be permissible or allowed. The following dimensions not to exceed: Throttle bore of 1-11/16”, Primary venturi of 1-1/4” and secondary venturi of 1-5/16”. Booster venturi shall not be modified from original and must be mounted in the original location. A carburetor test gauge kit, 7864 for Holley 0-4777 series 650 CFM Carburetors is available from BLP Products, 1015 West Church St. Orlando, FL 32805; phone 800-624-1358. It will be permissible to use epoxy to keep the booster venturi in place. Metering blocks are to remain unchanged from original. Milling of chock horn is not allowed. The choke assembly may be removed as well as any linkages that are not used. Power valve may be blocked. Accelerator pump nozzles and inlet jets may be changed. Accelerator pump must remain stock at 30cc. Any fl oat may be used that fits in the fl oat bowl. Any device to prevent fuel sloshing may be used. Jet extenders are permitted. All other existing motor rules apply.

50.6 The Racing Crackerbox

2008 APBA RULES • Inboard Racing • 35

50.6.1 All offsets are measured to outside of planking. (See illustration)

50.6.2 Boat must be planked with minimum 1/4” thick plywood.

50.6.3 Cockpit must fall aft of stations 9. A minimum of 9 -1/2 inches must exist from transom to seat back for both driver and rider seats and these seats must be bolted in place.

50.6.4 Shaft angle and propeller location is optional but engine must be mounted forward of cockpit.

50.6.5 All dimensions in the table of offsets have a tolerance of one inch + except as noted below. PLEASE SEE CHART

Overall width Minimum Maximum

At transom - 55-1/2” 59-1/2”

At station 7 - 66” 70”

At station 4 - 56-3/4” 64”

Length 13.5” 15’6”

Measurement from base line to keel at stations 8 and 9 must be 1/16”

TABLE OF OFFSETS — measurements are in inches and sixteenths of inches

STATION 13 12 11 10 9 8 7 6 5 4 3 2 1 0


TO KEEL 0-10 0-6 0-4 0-2 0-1 0-1 0-4 0-8 1-0 0-15 3-12 6-12 11-0 22-10


TO CHINE 1-1 1-0 0-15 1-0 1-4 1-11 2-6 3-6 4-12 6-10 9-0 12-1 15-15 22-10


SHEER 15-0 16-11 18-7 19-12 20-12 21-8 22-0 22-6 22-10 22-13 22-14 22-12 22-12 22-10


DECK 18-2 19-11 21-1 22-12 23-11 24-5 24-10 24-13 24-13 24-12 24-6 23-15 23-8 22-10


CHINE 29-7 30-3 31-0 31-12 32-6 32-14 33-1 32-11 31-11 29-11 26-1 20-8 13-4 0-0


SHEER 27-7 28-11 30-1 31-3 32-3 32-14 33-5 33-7 33-0 31-8 28-10 23-9 16-0 0-0

Basic Box Design diagram


50.6.6 Vee drives or gear boxes shall not be permitted.

50.6.7 Boats shall be not more than 15 feet 6 inches long or less than 13 feet 6 inches measured from bow to transom. All offsets are measured to outside of planking. Allowable deviations not to exceed one inch from frame No. 4 to No. 13 inclusive. On all measurements shown forward of frame

No. 4, the bow may be altered to suit. All dimensions in the table of offsets have a tolerance of one inch (plus or minus) measurement from the base line to keel at station #8 and #9 must be 1/16th of an inch.

50.6.8 The space between stations 9 to 12 is to be utilized as the cockpit space and the engine shall be mounted ahead of station 9. The minimum distance from the transom to the tip of crankshaft is 53”.

50.6.9 The bottom shall not have longitudinal or transversal steps including relieved chine or concavity. The hull to be constructed of wood frames covered with plywood not less than 1/4 inch thick. Fiberglass hull must be built in accordance with the specifications and limitations set out, as are wooden hulls. Wooden frames will not be required. All frames and station numbers will be converted into inches to determine the same location of cockpit and engine as in the present design.

50.6.10 Boats to be raced with two persons on board — no exceptions.

50.6.11 Rudder assembly, prop shaft size and angle may be optional.

50.6.12 Adjustable plates mounted at the rear of the hulls will be allowed provided they are not adjustable while the boat is in motion and provided they do not intercept the bottom of the hull longitudinally or transversely by any form of break or step. In no case can this plate be considered in measuring length of boat.

50.6.13 Fuel shall be gasoline of a type available for automotive, marine and aviation use. For the 275 cubic inch displacement engine only, methanol fuel may be used.

50.7 Couplers between in and out boxes and propeller shaft for Cracker Box boats shall be a minimum of 3.5 inches long and utilize a minimum of 4 clamping bolts. Set screws shall be used in each end of the coupler. Each shaft shall be dimpled to receive set screws. A safety collar on the propeller shaft, within 0.5 inches of the leading end of the strut or a safety collar within 0.5 inches of the shaft log assembly is mandatory. Safety collars must be configured so they will prevent the shaft and propeller from sliding back and hitting the rudder. Safety collars in all classes shall be machined from bar stock, not pressed metal (sintered iron).


We would like to thank Suncoast Framing Company, Inc. for their previous sponsorship.
© 2007-2008 Cracker Box Racing Club