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Class Legality

UIM · Hull and handling

Aftermarket or prototype hull, UIM

The highest-stakes eligibility question, and UIM's answer is binary.

This page is UIM only, and the bodies do not agree. The same part under IHRA and IJSBA. Which one applies to you is decided by whoever sanctions the race you enter.


UIM's production threshold is 50 units against IJSBA's 500. A small-builder hull can clear UIM homologation and fail IJSBA's outright.

Where it stands, class by class

24 classes, grouped where the same rule gives the same 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 borrow another class’s rules and are marked below; for those, the link to the parent class is read from the categories table rather than stated in the rulebook. 8 publish no rule for this part and name no parent to borrow one from, and are grouped together at the end.

What each answer below means

Not legal
This comes off. The rules refuse it in this class.
Legal, with conditions
Keep it, but measure it: the rules permit this part only inside stated limits.
No rule published for this class
Unanswerable here. This class publishes no rule for the part and names no parent class to borrow one from, which is an absence in the rulebook and not a permission.

Not legal 11 classes

Homologated production craft only - 50 specimens, marketed, conformity certificate.

Legal, with conditions 3 classes

PROTOTYPES EXPRESSLY PERMITTED via a UIM-issued logbook, valid 4 years, presented at every event. GP2 and GP3 homologated craft are also eligible. · 500.02.02

Legal, with conditions 2 classes

Prototypes expressly permitted via the UIM logbook. The 50-specimen threshold does not apply. · 500.02.02, 502.04-08


Aftermarket or prototype hull: 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 · checks on parts the shop sells · how this site reads a rulebook.

Hull and handling · two and four stroke · legal in 5 of 16 answered, all with conditions

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