Jets and trannys

[Hows Hatt]

Saw an outboard motor with a water jet in place of the prop this weekend and it made me wonder why are there not more jet drives on Hatt-type boats? And while I was wondering about propulsion systems, I also wondered why boat trannys don't have multiple gears like cars and trucks? Yeah, I don't know much, but I'll bet others have wondered also. Thanks. Howard in west Michigan

 

[Genesis]

Jet drives are not as efficient as standard props. As such you need more mustangs for the same throughput.

They become better at higher speeds.......

As for gears, there is no point. There ARE some two-speed ZF gearboxes, which a few boats have used that idle at unacceptably-high speeds otherwise.....

 

[Jaxfishgyd]

Jet drives are great........ If you're running the Colorado River.

The amount of extra HP needed to get the same amout of push isn't effective on boats of ours size.

 

[Passages]

I'm basing my comments on a couple hours on my buddy's 16' jet boat.

Low speed manuerving is dicey and while you don't have props & strut to damage, fouling your intake or impeller with a stick or plastic bag will bring a sudden stop to your fun. That's exactly how our afternoon ended - a 1/2" stick fouled the impeller. Fortunately, happened at the boat ramp getting ready to haul out.

I've seen some 40' boats with jet drives. They looks great underway, but I can't imagine backing into a slip....

 

[Passages]

Let me amend my comment above. I was on a jet boat that was impressive. The High Speed ferry between Maine & Nova Scotia. 4 huge jets kicking out and incredible 100,000 gps (yep per SECOND).

Cruised at 50 mph. Tied up without a problem using side thrusters. Way cool ride

See link:
http://www.catferry.com/the_ship/

 

[spartonboat1]

I store outside with a large ferry operation. I like to gab with both one of the owners and also their yard manager. At one time they ran jet drives and also jet (read turbine) engines on one of their big catamarans. Yes they were fast, but consumed prodigeous, i.e. prohibitive amounts of fuel, so I was told; and that was before the big runup in fuel prices.

The cost of operation related to fuel consumption quickly brought that prototype to a quick end. They now run Cat C-18's (sorry, I have forgotten exact model #), but are one size down from the largest CG cutter on the Great Lakes.

 

[SKYCHENEY]

Hey Spartonboat. Is that Sheplers or Arnold you are talking about?