Hydrojet boats

[marcochi76]

Hello,
the topic regarding the AB Montecarlo 55 caught my curiosity regarding the Hydrojet propulsion, that seems to offer a lot of advantages:
-handling
-consumption
-maintenance: all critical parts (pumps, impellers) are located inside the boat and above the water line and thus easy of access.

So why it is almost impossible to find that propulsion on boats of 35-45 feets?
We can find it on some superyachts (Mangusta, ...) and small tenders. But nothing on the most usual size boats.
Would'n it be a wonderful alternative to our lovely DPH legs?

Thanks for your inputs.

 

[vas]

are you sure about the pros you are mentioning?
I've got a jetrib which unless I'm mistaken shares the same principles of operation (if not ignore!)
Experience says that handling at low speeds is atrocious (ie non existant unless you have some jetpumping water some direction) and I'm pretty sure that impeller (well propeller if you wish) is in the water.
Only clear advantage is that you cannot chop a swimmer to pieces (and the reason I got one in the first place tbh having small kids around at the time ).

V.

 

[Bouba]

I think midrange boats are heading to a different trend...outboard powered

 

[Portofino]

I think you have external steering rams on most jet drives which risks seals being compromised .
Also it’s difficult to clean the impeller .Apparently despite being in almost total darkness they do crud up and are even more sensitive to crud than Arnesons.At least with Arnies you can see them and lift them somewhat .

Commercial ferries running daily are better suited obviously. Crud is a none issue .

They pick up periodic horror bills maintenance wise .I noticed flicking around looking at the AB 55 one had just spent €6K on the jets alone .

As I said even though the AB manufacture’s design team made a deep V sea worthy hull with jets , with the others like Arno Leopards etc they tend to at the stern go the other way flatten out reduce the deadrise to get lift .
That might be ok with 50-60 tones and 80 ft , but no so ok with 15/ 18 tonnes and 45-50 ft in terms of slamming etc .

Those NZ Hamilton jet drive boats are famous for spinning about up rapids because they can due to the flattened aft .

As said on the other thread the AB guys done well with them .I think the speed benefits bigger boats to carry the fuel load .
Not sure if a 45 ft hull could carry enough fuel to run the motors within a inch of there life to reap the lower Nm / L benefit ?

 

[Portofino]

I think midrange boats are heading to a different trend...outboard powered

Maybe in the states , but in the EU with fuel bills etc I can’t see a future in triple or quad outboards…..sales taking off .
Diesel even VP IPS ( for newbies ) will be too tempting in this segment the 40-60 ftr .

As well as trad shafts of course.

 

[Bouba]

Maybe in the states , but in the EU with fuel bills etc I can’t see a future in triple or quad outboards…..sales taking off .
Diesel even VP IPS ( for newbies ) will be too tempting in this segment the 40-60 ftr .

As well as trad shafts of course.

I saw a RIB with a 300hp Cox diesel the other day....and I think the outboard trend is here as well...it’s so easy for manufacturers to make an outboard boat...and sell them real cheap (without mentioning the 90K for the engines on the sticker)...the super high capacity outboards are the game changers

 

[Greg2]

Low speed handling with twin jets is excellent - once you get the hang of them you can move the boat in virtually any direction although low speed tracking can require a bit of work on the helm.
Economy not so good - they use more fuel than other propulsion systems such as outdrives and shafts.
Maintenance - lift out required for big service.
Choosing them at the time of build / purchase is also expensive compared to other drive systems.

Just some thoughts based on experience with Hamilton waterjets