Why aren't more boats propelled through tunnel drive?

Aren’t they restricted to catamaran hulls, and therefore considerably more expensive?

The balance of all the variables is pretty tough to meet. As the boat gains speed, it also wants to get lift because of the aerodynamic design. But the boat has to be built such that it won’t launch and flip over throughout a range of speeds. I imagine the engineering is quite complex and therefore much more expensive to put into practical use.

@stanleybmanly -No. Penn Yan makes them and I believe some cruise ships have them.

A regular outboard if a prop hits something you can simply replace the shear pin and prop and you’re off. A jet boat will need lengthy repairs.

@seawulf575 Penn Yan has been making them since the late’20’s, I believe.

@ARE_you_kidding_me -Tunnel drive is not a jet boat. The props are protected within the tunnel or tunnels.

The hull has to be made for a tunnel drive.

@lucillelucillelucille Yeah, Penn Yan makes them, but you asked why more boats weren’t made with them. Penn Yan has probably worked out all the kinks whereas another company would have to recreate the wheel, so to speak.

I want to get this straight. I understand that the tunnel hulls are great for shallow drafting, but I thought they required twin counter rotating screws installed in twin hulls, and are thus considerably more expensive and impractical for smaller boats.

@Tropical_Willie -Right, but why don’t they manufacture more of these types of boat?

@seawulf575 -I’m sure they have.
It seems that if one builds a better mouse trap.it doesn’t necessarily mean they’ll beat a path to your door.

@stanleybmanly – They’ve also made them in single screws for a long time.

Penn Yan’s patent for hull.

@Tropical_Willie -I read it through a few times and saw that it said expired. (jk! I just saw expired) :)
They don’t have a lock on that idea though as I have seen it on cruise ships.