No, that's right. 317 shp at 35,000 power turbine rpm. It's only an itty bitty helicopter engine out of a Jet Ranger after all!
You can hear what one sounds like here
Actually it's not as daft as it may seem. There's even a conversion kit available for marine use. Have a look here
for another C18-powered boat project.
The engine weighs just over one tenth of a 300hp six cylinder turbo diesel. Should be a lot of fun