Jet Drive for 10m tour boat - weed and shallow water solution needed

Hi Matt,

My current boats handle the weed pretty well and they are based on a life boat hull just like the one at this link - http://gcaptain.com/maritime/blog/maersk-alabama-lifeboat-faq?7817 only the prop is not protected and they have a classic rudder.

What I'm looking for now is a planning boat with shallow draught and ability to travel those weeded lakes at slower speed - hull speed 7-10km/h. I considered stern-drives but I hear only bad things about them and I look for a worry free solution so jet drives seemed like a good alternative. Now after having all this discussions and advice I am convinced the jet drives will not work for me.

As this is a tour boat - work boat that has to put up with a lot of things I have to study what system works best as I have no experience with fast boats. The Konrad drives seem nice but hard to get and expensive. Outboards are also an option but not economic when it comes to consumption and durability.

What else...

 

Richard, the man clearly is an expert. What he meant to say is: the props are well protected in the boot of a car while driving through a tunnel.

 

A jet will not work for you. The photo of the jet boat has a stomp grate on it they call it weedless but it fails.
Think of getting a drink out of a cup full of spinach and water the pump (straw) will clog and need cleaning.
I run small jet boats "Mokai" and weeds are a problem when it fills with weeds you need to throttle down and get to where you can clean it out.
I have seen a Hamilton suck up a dead rotting moose it was really bad, even the stomp grate did not help.
Seen a boat with a paddle wheel on the back that loved the weeds it just had no speed but weed were on problem.
There was a cavitation plate extender called Riffle Runner that allowed you to raise motor and keep water to prop it worked in the weeds too.
I think a mud buddy or surface drive would work.

 

A mud motor , tunneled and protected by a weed deflector skeg will work.

We used normal tunnels, weedless props in aperture, with a inspection port over the prop to lower a hand operated weed hook for bad fouling. We operated in intense vegetation.

Weed boats and harbour garbage boats are prop driven


Weed props

http://www.miwheel.com/Propellers/Industrial/Weedless.aspx

 

Yap Michael,

I know this things work as my current boats are just like that. The only problem is that now I need a boat that can go fast with low wake on main channels and than slow for the tourists to enjoy it on the small lakes ... that sometimes are full of weed and shallow.

 

Sure...they can go plenty fast. make the boat Long and thin with light displacement. take inspiration from these designs . notice how small the wake is.

http://www.rumerys.com/Seatrials.html


protecting the prop to deflect weeds and use an inspection hatch above the prop for cleaning when you do foul.



You might even be able to use a long axe bow boat to your advantage. Nice weed breaker forward on an axe bow. Ask a young naval architecture student to play with the design...weed blocking skeg....hollow tunnel aft to get the prop up high and parallel to water line....perhaps a planning board swim platform aft...anything to keep the boat riding on its lines at say 12 to 15 knots. perhaps use a sail drive type underwater unit ? or a simple outboard motor set forward in a well

uffa fox design

 

Opps...forgot

http://www.boat-links.com/Atkinco/Photos/RescueMinor/index.html

 

Pretty obvious Cornelis! We should listen to him, he even knows "mud motor´s". A alternative to Diesel maybe?

Jodani,

I am quite familiar with the Delta.

The SPJ 22 is 380 kg and accepts 150 hp in C rating, which would be the right rating for such purpose. Two of them are capable to propel a 10 meter boat at around 20 knots. I thought that would be in your ballpark.
Apart from Hovercraft the only solution I am aware of, and Hovercraft are not what one needs in such environment, far too loud.

Regards
Richard

 

Here is a plan idea I was able to draw with my limited skills of what I had in mind.

As it is a tour boat the structure is based on a catamaran type so I wonder if it would be possible to use two hulls like the ones Michael showed http://www.boat-links.com/Atkinco/Photos/RescueMinor/index.html

- what would be the max speed of that and what power will be needed to achieve it when loaded with 15 people. The boat will be build of aluminium.... any estimates would be welcomed

- Would that hull in a single form be stable enough to be configured like the attached design?

Thanks and hope I'm not tiring you with idiotic questions...

 

I am happy you are familiar with the Delta so you know what I'm talking about. The SPJ 22 would be ok but there's still the weight problem as:

SPJ 22 x 2 = 380kgx2 = 760kg
Yanmar 160hp x 2 = 320x2 = 640kg
Total equipment weight - 1300kg ... how would this weight influence draught and performance on a planing hull?

 

First,
forget about the Atkin boat, thats a floating weed eater. And too small on top of that. So much about Michaels recommendations.

The cat idea sounds nice, but isn´t. these craft get stuck too easily in the conditions you have there. A more or less flat bottomed boat with these PJ´s would be the better performer and carry more weight. Cheaper on top of that.

look here


This one is a rather heavy boat, and does well with 2x 130 kW. You should contact Schottel and ask them for similar craft built!
Of course the top range of speed you will never achieve with these heavy pump jets, but you will be able to go deep into all of the smallest channels, you could never explore with a speed optimized vessel.

Regards
Richard

 

jet drive for 10 m tour boat

Why not stay with simple tried and proven propulsion..with added advantages and any reasonable engineer should be able to make one to suit your needs,or even home handyman. It is mechanicaly the same as a conventional inboard shaft drive..except that it can be lifted up ( to clear weeds) or droped down. You can use surface propulsion technology if you want. It can be built from cheap material or stabalised stailless steel. Two unit would be great for your purpose and woul cost less that a sophisticated expensive drive. heavy diesels would be no problem and the drive can be kept simple to stop weeds clinging. All parts are conventional and readily available most places. Incorporate your own ideas. The unit makes the hull stronger where you need it,at the transom.

There is no u/v joints in the water and the motor does not move with the shaft as it lifts. All mechanical parts are safe from the water inside of the hull.
It uses the same parts as a standard inboard drive and has many more advantages than a fixed inboard drive.

 

Yah Tom, go simple...thats how the mud motors work. They are indestructible with steel props and they can chop thru anything. The important part of any rig is simplicity and fabricated locally from available materials. The cat idea is great for a tour boat. Problem with cats is they are expensive to build.

A cat could be make into a "weed eater" trimaran . Not a true tri but a cat with a center pod. The outside hulls would carry your cruising power. Conventional skeg protected props. The centerhull would carry your weed motor. The weed motor would be cheap to custom build since it would be very low power....just for chugging thru the weeds with tourists bird watching....then once clear...main propulsion for cruising upriver.

Mud motors are simple...the props are home made steel screw type.

 

Hi Richard,

I found this boat for sale http://www.schravenbv.com/sc-alg-body.php?tc=en&ve=m&hf=1&pa=14&su=0 using this propulsion but I still don't understand how is this different from a normal jet and why would this be impervious to weed?

If the pump encounters a mat of weed that will be sucked into the greed and eventually block it. How do you clean the impeller inside that drive? In a jet "seams easyer" to clean but in that you will be forced to take the boat out. I think you can't reverse that impeller either.

Will ask Schottel about this and see what reply I get fro them. The idea of having that system is appealing and practical.

@Tom and Michael

I was thinking about that drive system but I don't think it would do well for long hours of usage as that joint there is not so efficient and I had problems with them on my current boats. I have found this:
http://au.alibaba.com/product/330029879-MSD250-Surface-drive-propeller-for-speed.html
http://www.nauticexpo.de/prod/msa-m...ive-antriebssystem-fur-boote-24647-96379.html

That seem to be the same principle just like the Arnesons but I don't know how hard it is to get them to work properly under different boat loads. Could you use ordinary props with them instead of surface drives? And could such systems work completely submerged by eliminating the steering part and just using the trim?

I think Richard has a good point by recommending a flat bottom as this will give a shallow draught and good stability (not as good as a trimaran but close).

...well confusion sets... when in the hole stop digging...

 

You can also use an outboard (s ) mouted high on the transom with a surface drive prop.