Aparently there has been some debate about the ability of our club being able to uphold the rules
as written by IMPBA. I am posting the IMPBA sport tunnel rules, for those who have entered and may not be familiar. These engines will be teched by the CMB club before the race, and the top three will also be teched after everyheat, just like we do at the internats. We will be using the Go-No Go gauges after the heats. Please NOTE: If you are found to be out of compliance with the rules, you will be disqualified. Now is the time to make sure your stuff is ready and legal. If you have questions, now is the time. The entire IMPBA rulebook can be viewed online at
www.impba.net
~James
Sport Outboard Tunnel Rules
Engine and Hull Specifications
1. There shall be one engine class, Class B.
2. The Sport outboard class shall use tunnel boats only.
3. The Sport outboard tunnel class shall not lock down the engine or use any
auxiliary steering system.
4. Original carb bore and exhaust configuration will be retained as
manufactured. No modification to the carb bore or exhaust outlets will be
allowed.
5. No high performance exhaust systems (tuned pipes) will be allowed, even if
they are offered by the manufacturer of the engine. Clarification: the two
outlet exhaust / muffler chambers offered by K&B and O.S. are not
considered tuned pipes and will be allowed in the Sport outboard tunnel class.
Engine Specifications
1. Engines must be standard factory production with a minimum of 100 units
available for sale to the general public. To be eligible for the International
Regatta the engines must have been offered for sale to the general public not
less than ninety (90) days prior to that year's International Regatta.
2. The powerhead and lower unit must be of the same manufacturer and model.
3. The engine external parts shall remain as originally manufactured within
series except as shown in Part 4. Clarification: No water-cooled engine parts
shall be used with air-cooled engine parts. Common engine parts that are used
on both engines models may be interchanged. Slide valve exhaust adapters
may not be used with carburetor equipped engines.
4. The following exceptions will be allowed in the Sport Outboard Tunnel
specifications.
a. Adhesives (loctite), set screws and jam nuts.
b. Any carb linkage arms.
c. Any motor mount.
d. Any glow plug, fuel brand and mixture.
e. Any type steering arm.
f. Any flywheel nut.
g. The lower unit below the cavitation plate may be trimmed, sharpened
or polished. No material shall be added to the lower unit.
h. Adjustable mixture controls will be allowed, however the original
needle valve must remain in its original position.
Sport tunnel engine inspection procedures
The maximum carb bore and exhaust outlet bore size shall not exceed 0.320 inches. These
may be checked with a 'GO, NO-GO' gage or dial calipers. Note: It will be the contestant’s
responsibility to check and verify carb bore and exhaust outlet bores prior to the contest. Any
infraction concerning the carb or exhaust bore sizes will result in immediate disqualification from the contest
. TB
