UIM · Driveline
Legal in every class, but diameter is the constraint below GP2.
For every class below GP2, publish the impeller diameter next to the OEM diameter. That one number decides legality.
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. 8 of them publish no component rules of their own and are marked below; for those, the link to the parent class is read from the categories table rather than stated in the rulebook.
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.
Governed by the parent class 8 classes
No component rules are published for this class and no single parent class is named, so this part cannot be answered for it. That is an absence in the rulebook, not a permission.
Legal, within limits 7 classes
Original diameter maintained.
Legal, within limits 2 classes
Modified or aftermarket impeller provided THE ORIGINAL DIAMETER IS MAINTAINED. · 501.01.06.01
Legal 1 class
502.03.09
Legal 1 class
Diameter constraint lifted for two-stroke; impeller, housing, stator, plate and shoe all modifiable. · 501.03.09
No rule, this is an open class 3 classes
No driveline article.
No rule, this is an open class 2 classes
No article covering this part. Free under the open-list reading of · GP1.
Aftermarket impeller: 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 UIM class · where the rulebooks differ · signed checks on parts the shop sells.
Driveline · two and four stroke · legal outright in 11 of 24