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Old 30 December 2002, 12:54   #11
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Well done Dirk.
OK, I apologise for casting nistersions then.
I was suspicious of your accusation initially as I have not been too keen on the tone of some of the comments on this forum recently, and would hate it to be somewhere where people make unfounded accusations.
I am sorry if I doubted you in this instance and well done for broadcasting something that might effect more people (me included!).
Chris, who races, does have something of a reputation for driving his boat really hard. Let us hope that it doesn't happen to too many of us.
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Old 30 December 2002, 13:33   #12
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Is it not also fair to say that the bravo 3x drive is not a good long term proposition and weather the Bravo 1x drive is any better is uknown at this stage?.

This is what I have heard and that the Bravo 2x is indeed a far more heavy duty drive leg.
Just you get Torque steer if it isnt set up properley as its a single prop.?

Becouse there are so few out thereThe Bravo2 is still a little uknown,

Surley the hull flexing will couse the engine block to crack and the drive iis down to the engine makers.?
Am I wrong here with my maths,and if not why did nobody say something earlier,and stop there friends making the same mistakes,with Drives and engines?

Crazyhorse?
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Old 30 December 2002, 13:44   #13
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When I first bought my Yanmar and Bravo 3 it was on the advice of Scorpion and their engine/leg supplier.
When I started to have problems I looked round at the alternatives and could not see anything with a better reputation.
That, of course was two years ago.
I have to say, my engine has been faultless-but what is one to do?
Even today. Would anyone recommend a better and more reliable combination or is what we are doing with ribs, just pushing engine/leg technology to it's limits?
If the later is the case then we must live with it or take up growing corn. That's pretty unexciting.
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Old 30 December 2002, 13:57   #14
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Brian your right,

But lets not fool ourselves Here.

The block will crack if the hull/engine mounts are not designed properley and the stress comes from the hull with its continual twisting of the engine/s,and the leg will go, if the gearing or shafts arnt designed correctley for there intended use.

Thats my take on this,at present?
As you say,We quite rightley make the best decision at the time.
In my case,They already brought out another gearbox that retro fits onto a kad 44.My engine only been out 12 months.?

Crazyhorse
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Old 30 December 2002, 16:47   #15
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Hi folks

The Bravo drive saga will I think never be resolved.

Some people swear by them some swear at them.

I was fortunate to spend some time on holiday with a few commercial RIB operators is south wales, a great bunch.

To sum up there comments,

Typical Ribs 9M with Yanmar 300's

Typical use, 12 hours a day, 7 days a week during the summer months.

Bravo 3X multiple failures they dont think this is suitable for commercial work loads
Bravo 1X, never tried
Bravo 2X, now using and to date much better.

However they said they would look for alternatives to the Bravos for future RIB's.

Anyway based on this I have gone Bravo 2 for my new RIB.
While I know is not as quick as the Bravo 3 it does appear to me more reliable.

It would also be interesting if people know if adding showers makes outdrives any more reliable.

Regards Gary
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Old 30 December 2002, 17:21   #16
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Garygee

is your Yanmar a 4 or 6 cylinder.
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Old 30 December 2002, 18:17   #17
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Yanmars

If you need any info on a good brace to fit `get in touch with DAVE CRAWFORD MARINE.
I have just got my 300 Yanmar from them and they will make the braces for you, and they seem to know what they are on about.
You can contact them on 01590 671251 Fax 01590 678380
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Old 30 December 2002, 20:44   #18
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Engine Block Strength

Anyone know of a broken block on a KAD?

JW.
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Old 31 December 2002, 02:55   #19
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The Bravo 2X that came with my Yanmar 300 was spec'd on the advice of Barus. There is no appreciable torque steer that I am aware of.

Any heel always appears to be the result of water conditions and is easily corrected with a few degrees of opposite side trim tab.

Because I only fitted the new engine right at the end of the summer I have only got 50 hours on the clock. It is probabaly too early to tell whether or not I've got - or am gonna have - the problem we are discussing here.

However, if I do it will be bad news for those of you that have the same engine and like to throw your boat about in the manner of a rallycross 4x4 while driving flat out. I use Magellan Alpha rather more like an old Bedford truck than a Subaru Impreza!
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Old 31 December 2002, 04:05   #20
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The sad and sorry story is " There is no such thing as a good gearbox"
I know this from experiance as it has been my day job for 33 years and if they didnt go wrong I would be out of a job!
This simple fact is, a stern drive unit has so many moving parts that it is impossible for them not to break. I undertook a three year test programe with Yamaha to establish why the Hydradrive was failing on certain boats. Our findings where a mixture of bad fitting practices and a problem with the lower gears. Once the gears had been modified Yamaha had very few failures with the exception of certain boat owners who beat the living daylights out of the boat everywhere they went.

I belive that Stern Power in concunction with Mercury make a unit that can take a 1000 hp but this needs a gearbox in front of it and weighs in at a massive 300kgs.

Most boat builders are looking to save space and it is a source of consant amayzment that they try to re-invent the wheel instead of looking at what works.
If I was building another boat I would look at putting the engine in backwards and running a shaft through a "V drive" and rudder. In test's this system gives the longest hours with a 30 foot fast fisher doing over 5000hours without any problems.
Altenativly I would run a jet directly from the flywheel and use the bucket as the gearbox. Of course I would have to fit a bloody big self righting bag to turn it over when it broached in a big following sea and lost drive !

As for the engine mounts breaking on Yanmars all the beefing in the world will not stop this. Again it is a simple case of maths ie.
Downward force over upward force must be equel. If the engine has a heavier G Force at the point of impact with the wave, it is the block that cracks. The Yanmar engine is only a truck based unit and was never designed to take the kind of shocks that are being generated in a boat. the only way round this is to mount the engine in a different way. Again there is a wealth of experiance out there it just isnt being used because the builders of the boat are to proud to ask and rely on the customer to develop the boat. Alternativly, Dont jump waves, If you want to fly buy an aeroplane. Boats float Planes fly. If anyone needs any further information contact me by private mail. Alan P
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