IHRA · Engine

Engine block substitution

IHRA answers this part for 24 of its classes. 2 of those answers are permissions, with or without limits attached, and 22 are not. 21 are inferred from how the class is written rather than quoted from a rule naming this part.

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This is one body's answer, not the sport's. You are bound by whichever body sanctions the event you enter, and where both govern you, you are held to the stricter of the two. The differences are set out in the rulebook comparison.

Where it stands, class by class

24 classes, grouped by the answer rather than listed one by one, because an answer that holds for a class usually holds for every class that borrows its rules.

Not permitted, not listed in the rules Our reading, not a rule we can quote at you. This class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list.

No rule, this is an open class Our reading, not a rule we can quote at you. This class carries no stock clause at all, so anything unlisted appears to be open. The rulebook does not say so in terms.

OEM part required 1 class

Must remain OEM. Four-stroke entries: Internal modifications allowed. · V.4.5

• Sport GP

Not permitted, not listed in the rules 18 classes

On a closed list an unlisted modification is not permitted. · A.2.2, J.1

• Runabout Endurance
• Runabout Lites
• Four-Stroke Ski Lites
• Runabout GP2
• Runabout GP3
• Ski GP2
• Drag, Sea-Doo vs Sea-Doo
• Drag, Yamaha Pro Stock
• Drag, Sea-Doo Pro Stock
• Drag, Yamaha Spec
• Ski 1100 Modified
• Ski 1500 Modified
• Ski GP3
• Ski Limited
• Drag, Sea-Doo Spec
• Runabout Limited
• Drag, Super Stock
• Drag, Turbo No Nitrous

Legal, within limits 1 class

1101cc+: blocks interchangeable across any OEM manufacturer EXCEPT the 1500cc Kawasaki SX-R which must use the manufacturer's block. 1100cc and below (K.3.6): donor block must be 1100cc or less. · K.2.6

• Ski GP

Legal, within limits 1 class

Must originate from a production runabout watercraft. Only limitation is the cc limit. Interchanging top decks and engines permitted. · X.2.7

• Runabout GP

No rule, this is an open class 2 classes

The class states only what it bans and calls itself run what you brung, against a section DD preamble that says anything unlisted is illegal.

• Drag, Stand Up Unlimited · DD.10
• Drag, Unlimited · DD.6

No rule, this is an open class 1 class

No restriction in section CC, and CC.1 permits any modification it does not restrict.

• Freestyle · CC

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Engine block substitution: if the rule your class applies reads differently to you, or the rulebook has changed since this was read, ask. We answer with the section we read it from, or that we have not read it. Ask a rules question.

Every IHRA class · where the rulebooks differ · signed checks on parts the shop sells.