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[TomHugill]

Hey folks, I've just bought a graupner moonraker and want to improve the performance. I've already got 4s packs to run it on. So I've been told the graupner impeller is rubbish, so has anyone tried to use the kmb 28mm jet impeller in the 28mm graupner jets?

I know I could get the kmb jets, however this would be costly and necessitate rebuilding the rear of the boat to fit them.

[Robert Davies]

May be worth asking at Snikwah's model jet boat forum:

http://modeljetboat.com/forum/index.php

[Time Bandit]

Kehrer Impeller will not work in Graupner jet units.
the distance between impeller and stator will not fit amd this is one of the most important things regarding efficiency.

Better would be to improve the jet units since most of them are build like s....
make all edges round especially the intake.
check the inner surface of the jet units.
everything must be smooth an without edges.
If built good Graupner jets have the same power as Kehrers.

And finally check the hull. The edge of the hull must be sharp also the edge before the trim tabs. Dont make anything round here.

Which motors do you use?
I have been using the Kehrer Neodymium 700s at 4S Lipo.
This gave a speed of around 30km/h.