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nzjetboating.com Forums => Tech Library => Topic started by: Fuges on December 04, 2012, 21:35:48 PM

Title: Unit height for wee boats?
Post by: Fuges on December 04, 2012, 21:35:48 PM
A newbie here, about to build an intake unit for a 3m boat, I have noticed most people build the intake with around 100mm from the delta to the underside of the pump, where is on the jet ski the unit is mounted hard down close to the delta. How does this effect the handling of small boats and is there a reason for raising them up?
Title: Re: Unit height for wee boats?
Post by: Jeff B on December 04, 2012, 21:47:09 PM
I make mine about 50mm high from the bottom of the boat to the bottom of the unit. If its too low you will smash your nozzle off on rocks as the unit is usually stuck out the back of the wee boat. I doubt the unit height will affect handling. I don't think it affects performance much either although someone else will say different.
If using the ski engine you can mount the unit low but some car engines have deeper sumps hence raising the unit up.
Title: Re: Unit height for wee boats?
Post by: Fuges on December 04, 2012, 21:52:13 PM
Thanks Jeff, using a kwaka 900 ski engine and unit, just thought it may get to a point where it forces the nose of the boat down, but I guess this can be compensated with a wedge in the nozzle.
Title: Re: Unit height for wee boats?
Post by: Brizz on December 06, 2012, 16:41:03 PM
Whatever the crank center allows plus clearance from bottom of motor to hull, eg Kawasaki 15F is 130mm crank center to bottom of sump and I am allowing 40mm (for big dents) sump to hull so center of unit shaft to delta = 170mm. The height should have negligible impact on bow position only the tilt of unit.  Most jetski std are level.       2c