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Jet Powered Tuffy

Posted: Thu May 31, 2012 6:59 pm
by ettiwd
I am planning to build my third GlennL boat. The first was a Malahini (great boat) and the second was stripper canoe. I want to build a jet boat by graffing a Sea-Doo XP 1996 787 cc. I understand all boats would need modification. I have selected the Tuffy. I wonder if anyone can tell me the disadvantages of this selection. I wanted 6 foot at beam and like it's looks.
dnw

Re: Jet Powered Tuffy

Posted: Sun Jun 03, 2012 7:02 pm
by steve crawford
It is twice as heavy as the TNT.....

Re: Jet Powered Tuffy

Posted: Mon Jun 04, 2012 9:34 pm
by Caber-Feidh
Allot more to building a successful jet than hanging a pump on any of various assorted hulls.

Going to have to agree with Steve... as short and to the point as he is, his opinion is spot on. An overpowered pump with a relatively small intake area on a hull not moving fast enough to, or designed to feed the pump a clean water stream is going to be an eternal PITB that will end in cavitation damaged impellers, and a generally disappointing result.

*A jet pump MUST have a hull that keeps the foot in the water.
*A jet MUST have a design that keeps a positive pressure on the "suction" piece at all times, including cornering, flat out running.
*The intake must be deep enough to not have problems with parasitic cavitation under sudden acceleration.
*The hull has to provide a clean, uninterrupted flow column to the intake, and be able to do so through the entire expected speed range.

In the case of an overly flat hull around the intake, the surface boundary layer creates a condition in which the pump will begin to cavitate. The hull isn't applying enough pressure to the surface of the water and the intake is too close to the surface of the water, or the pump is drawing more water than is found in the column directly in front of the pump's intake, the laminar flow becomes turbulent, Simply put, (very much over-simplified) the water next to the hull is moving as fast as it can, the pump needs more, a vacuum develops, and your impeller dissolves amid a bazillion micro-vacuums, result - your boat basically just sucks... literally. Just grafting a PWC hull designed to feed the pump properly through a given operational envelope to a hull unable to operate within a parameter near that envelope is an exceptionally bad idea.

Could a jet tuffy be done? Definitely. But don't expect it to be as simple as hacking a 60 mph performance PWC off at the waterline, and gluing it to a hull that is much heavier, flatter, and designed for an outboard.

Just my 2 cents worth.

Re: Jet Powered Tuffy

Posted: Tue Jun 05, 2012 6:05 pm
by ettiwd
Thankyou both for your imput, points well taken. I have more research to do.

Re: Jet Powered Tuffy

Posted: Tue Jun 05, 2012 10:08 pm
by steve crawford
My TNT... I Veed the transom and it never starved out for water no matter how tight I turned....
You would need the 1200 Yamaha we just sold for that boat and V the hull al the way back to the transom....It would fly then....


WaveRunner specs....
Length 115.4"

Height 40.2"

Width 45.3"

Weight 673 lbs.

Engine 1176cc, 3-Cylinder, 2-Stroke

Horsepower 155hp @ 7000rpm

Seating 1, or 2 person/352 lbs.