Designed originally as an entry-level class, these small model powerboats provide large amounts of fun and spirited racing. They fall into two types:
Standard Z: 0 - 2.10cc (0.129 cu in) non-spark ignition glow engine, submerged drive only and no gearbox.

Modified Z: 0 - 2.10cc (0.129 cu in) non-spark ignition glow engine. Drive systems can be direct, geared, submerged or surface.

Not much bigger in size than a Z Class boat, these are a little faster, having a bigger engine. The smaller hull size is better suited to flatter water but can be used on the sea too.
0 - 3.50cc (0.21 cu in)      
Non spark ignition glow engine

A step up from the AA Class with glow/nitro engines from 3.51 to 7.5cc. These are fast boats with some modern hull designs being used to great effect. Spectacular racing on either fresh or salt water.

3.51 - 7.50cc (0.46 cu in) 
Non spark ignition glow engine
(All .46 size engines are approved for this class)

B Class boats are proper little powerboats and can take nitro engines between 7.51 and 11cc. They are not much smaller than some of the spark ignition boats and are proportionately fast.

7.51 - 11.0cc (0.67 cu in) Non spark ignition glow engine

Probably the fastest class in OMRA although this is now being challenged by some of the big petrols, C Class boats are big, powerful and very, very fast!   At home in rough conditions, these powerboats use big glow engines to great effect and they really are small versions of the real thing.
11.01 - 50cc (3.05 cu in) Non spark ignition glow engine

A petrol class aimed at those wanting to run a standard engine* or perhaps who are new to the sport.  RTR Boats of the requisite sized engine are also eligible to enter this class too, providing there is a fail safe and silencer fitted. Often supplied with a radio set, this really is cheap racing for all!
0 - 26cc (1.586cu in) Standard petrol engine Spark ignition only.

*Refer to the RULES section for full class specs.

E Class is OMRA's Evolution class and features some real monsters. Now perhaps as fast as the C Class boats, E Class boats are all petrol powered and so are [relatively] cheap to run and build.  The sound of these big engines coupled with big hulls makes for spectacular racing, especially in the rough stuff!

0 - 50.8cc (3.099cu in) Spark ignition only