7 Distinct "Thunder
on the Chain" Classes:
Lake
Racer Outboard
Pro
Modified Outboard
Lake
Racer Inboard
Single Carbureted
Multiple
Carbureted
Open Class
Blown
Alcohol Class
General
Boat Race Guidelines
Lake Racer Outboard
1. General Rules:
a. Hulls: Any open cockpit, full interior production hull
manufactured with minimum of seating for 3 people.
b. Engines: Only OEM outboard motor
components from like manufacturer may be used unless specifically
noted. No nitrous or any
other type bottle pressure injection. No bottles in boat,
solenoids disconnected. Powerheads and components must
be available to the public via a traditional dealer or
manufacturer
high performance division.
c. Block: Max of .030" overbore
allowed on Nikasil motors. Max of .060" overbore allowed
on steel sleeve motors. If metal has been removed from
deck, thick head gaskets
must be used. No dual plug heads. Yamaha and OMC may
run aftermarket
single plug heads.
d. Pistons: Must be forged or cast
aluminum. Keystone or Flat rings only. Pistons must be
OEM or approved
aftermarket pistons
(includes Wiseco, ProMarine, Vertex and Wizard).
e. Reeds: Aftermarket composite reeds
allowed. Any OEM reed cage allowed.
f. Ignition/ECU: Rev limiters may
be removed. No devices that enable the adjustment of timing,
ignition or
fuel curve
of the engine (mechanical or electronic) are allowed.
Driver may manually adjust overall lean/rich from
driver’s
seat. Brucato PCU and ACU are allowed. ECU modification
services must be available to all racers. OMC/Suzuki/Yamaha
may use
aftermarket Ignition/fuel injection including aftermarket
injectors, fuel rails and necessary bosses. Must
maintain OEM front half, intake and throttle bodies.
g. Fuel/Oil System: Multi fuel pump
setups must be wired in series and one switch must start
both pumps. Aftermarket
adjustable fuel regulators allowed. Carburetor
may be bored. After market velocity stacks used, OEM air
boxes removed.
Carburetor stuffers allowed. Oil injection may
be removed.
h. Gearcases: No small gear cases.
Must have forward-neutral-reverse shiftable from the driver’s
seat. After market nosecones allowed.
i. Flywheels: Flywheels on engines
running “260
style” ignitions
may be lightened using only OEM components
from like manufacturer. All other engines
may use
aftermarket lightweight flywheels.
All flywheels must maintain OEM magnets.
j. Exhaust: Aftermarket and modified
OEM tuners and exhaust adapter plates allowed. Modifications
to OEM exhaust adapter
plate allowed.
k. Midsections: Minimum mid section
length is 15”.
OEM midsection and clamp brackets may
be shortened. Aftermarket housing may
be used
with modified
OEM clamp bracket.
Liners
may be removed and housings drilled for
exhaust relief. No Champ midsections
allowed.
l. Cowls: After market stock appearing
lightweight cowls allowed.
2. Stock Engine Rules/Exceptions:
a. No metal removal or any
internal cylinder block mods allowed. No porting, polishing,
feathering. No piston, rod, reed cage, wrist pin, sealing
ring or crankshaft modifications. No lightning, balancing
or blue printing. Welding on cylinder block allowed for repair
only and must be machined back to stock configuration and
shape. All components must retain stock factory configuration
from the adapter plate up except as noted.
b. Compression values based on 12 volt starting subject to ± 3#
(pound) variance.
3. Weights and Brand Specific
Rules for STOCK Engines:
Mercury Outboards
a. 2.5 ProMax/Lazer EFI: Any OEM bolt
on and SVS allowed with 150# max compression – 1525
lbs.
b. 3.0 liter engines: Any OEM bolt on and SVS allowed with
130# max compression – 1550 lbs.
c. 3.2 liter 300XS – 1550 lbs.
d. 2.5EFI 260 (w/140# of compression on 12v starting max)
1600 lbs.
e. 2.5EFI 280 (w/260 Electronics and 145# max compression)
1625 lbs.
f. 2.5EFI 280 (w/280 Electronics and 145# max compression)
1575 lbs. (Alternator belt to remain functional while in
competition)
g. SVS allowed on 260/280 with 15 pound weight addition
OMC/BRP Motors
a. 3.0 liter motors may run 40cc heads, all others must run
stock heads.
b. 3.0 Liter Looper Carb – 1500 lbs
c. 3.0 Liter Looper EFI – 1550 lbs
d. 3.3 Liter Aftermarket EFI/E-Tec – 1575 lbs
e. 3.4 Liter Aftermarket EFI/E-Tec – 1650 lbs
4. Weights and Brand Specific Rules for MODIFIED Engines:
a. Engine modifications allowed. OEM outboard motor components
from like manufacturer must be used unless specifically
noted.
b. NO lightened crankshafts. Metal may be used to balance,
but not removed. Stock stroke only.
c. NO dual plug heads. Yamaha, OMC, and Suzuki may use after
market single plug heads
d. Stuffing allowed on all motors, block and front half only.
Mercury Outboards
MERCURY 2.5 EFI – SVS Allowed with 25# Weight Addition
a. 2.5 Liter 1400 Modified Production 1,775 lbs.
b. 2.5 Fabricated Z port motors 1,800 lbs.
c. 2.5 Bridgeport motors 1,800 lbs.
d. 2.4 Liter 1,600 lbs.
e. No welding or fabrication on plenum, 3.50” Max butterfly.
f. Fuel system must utilize OEM fuel rail, injectors, temp
sensor and ECU.
MERCURY 3.0 EFI
a. With stock fuel injection 1750 lbs.
OMC/BRP Outboards
Carb – 1700 lbs.
EFI – 1775 lbs.
Yamaha Outboards
a. 2.6 Liter (OEM Carb) – 1,700 lbs.
b. 2.6 Liter (OEM EFI) – 1,725 lbs.
Blarney Island would
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