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Old 07 February 2003, 14:53   #51
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Dirk,What exactly is this breaki piece and have you any experience of them failing on a regular basis and on what sort of drive/ boat/engine/use.?



Anybody else got any imfo on the DPX drive?
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Old 07 February 2003, 17:32   #52
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Breaky Bit

Dirk,What exactly is this breaki piece and have you any experience of them failing on a regular basis and on what sort of drive/ boat/engine/use.?

have heard of this before, and has been used for ages, picture the scene---------- high revving, and put the engine in gear, given this, and all the mechanical stuff that is going on, the spline will break, is used as a safeguard, so as not to knacker the rest of the engine/gearbox etc ---- a weak link, shall we say, same applies to going in to fast, slamming it into reverse, this 'weak link' may break, only really ever heard of it going with someone who did not care much about their engine eg. they did not pay for it, 'supposedly' the EDC does not allow this to happen, and have not heard of one breaking with an EDC? true or not, do not know?

Pete F
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Old 07 February 2003, 18:22   #53
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The weak link is a splined sleeve that joins the upper and lower down shaft in a Volvo DPX drive, might be on a DP drive as well but I've never been inside one of those. Mercruiser also use them on the Bravo, but not as a "weak link".

This drive was fitted to a single 8.2 litre petrol sportsboat, fitted with twin lever controls. Engine was revving high, drive put into forward, resulting in broken link. No big deal, replaced part in a couple of hours.

As for not caring about engine, it wasn't done on purpose, purely an accident, what we would call operator error.
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Old 08 February 2003, 09:25   #54
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Volvo have said the DPX drive is designed for boats in exess of 50+knts?

As its design is only for Fast applications boats.

They have also said that its not as efficient at around 30+ knts running with a Kad as the new DPG? I cant understand that statement so I have asked for clarification?To asses what they mean?Maybe its to do with all up weight or torque?

I have asked for the Internals to be sent through as I dont understand how a drive designed for 50 + isnt as efficient low down around 30/40+.There words were that it will be less efficient arround the slower speed than the DPG Drive and for cruising around 30/40+knts then withought dought the DPG is there recomendation for efficiency and longevity?

Im interested as Im going to buy a 2nd drive as a spare.

It also sounds that this Breaki piece may be worth having as it may save on serious damage.And is what designers call a built in saftey protection device.

We will see whether the DPG drive has one built in or whether it is designed in a totaly different manner for the different Primary application.

As the Bravo 2x is a commercial drive and if I had to go Yanmar then that would be my preferd drive for cruising not there racing drive.

Im interested in Longevity and strength for a commercial application, outright speed is of lesser importance on a Designated offshore cruising boat that will be used in a commercial manner and in varying weather conditions which is what our application is.Therfore a realistic cruising speed of 30 to 40 knts will be more than adequate for us,I will be a very happy bunny if I achieve this on a regular basis,as most offshore boats achieve far less than this,unless they are blessed with those exeptional conditions that arnt that preverlant offshore in the Irish Sea all yr round.


Thanks Seafrisky and Dirk and JW will update on imfo.
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Old 08 February 2003, 19:25   #55
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Weakest link

My Volvo man tells me that all Volvo drives have had this protection device for many years. However, he also says that in 20 years he's only ever seen 2 of them break. I've asked him to get a spare since, now I know about it, sod's law will ensure it breaks if I don't have a spare. The user's manual, that is supplied with my new motor, clearly states that it will not allow the engagement of a gear until the revs have dropped to 1000rpm. The gear lever can be moved but the gear change will not take place until the revs fall.
DPX - the dpx is a high performance/ high speed drive and, as such, it is not burried as deeply onto the water. On a heavy boat that is essentially load carrying, it is likely that the drive is not going to be as suitable as the DPG drive may be. On the other hand, if one is cruising at speed, the deep drive is causing unnecessary drag. Unfortunately, unlike an outboard motor, it is not easy to adjust the height of the outdrive. It occurs to me that, since performance is dependent on the outdrive height, a selection of distance pieces to allow adjustment would be a good idea.
JW.
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Old 08 February 2003, 19:37   #56
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The weak link seems to be a benefit see.

Aquamatic sterndrive
The DPX drive is designed for speeds in excess of 50 knots with Duoprop’s well-known features incorporated into a hydrodynamic lower housing.

The DPX drive features: cone clutch for easy and smooth shifting, pattern-matched spiral bevel gears for optimum strength and minimum gear whine, a break-away shaft coupling to prevent costly drivetrain repairs, engine coolant water intake on the drive, exhaust through the propeller hub, cavitation plate and transom shield for maximum quietness and low power losses.

So athe next Question is Have I got a Breakaway shaft on the DPG and sods law is also that I may also need one as a spare.

It also seems we have made the correct decisions with regard to our drive trains and there respective applications.

So far So Good.



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Old 09 February 2003, 06:25   #57
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[QUOTE]Originally posted by crazyhorse
[
Im interested as Im going to buy a 2nd drive as a spare.

As the Bravo 2x is a commercial drive and if I had to go Yanmar then that would be my preferd drive for cruising not there racing drive.

Crazyhorse,
A spare drive really is an unnecessary expense, especialy if I'm right in thinking that you are considering a DPX. The DPX & DPG are not interchangeable, the transom assemblies are completely different, the dpx benefitting from external hydraulic steering.

As for the Bravo 2 being a commercial drive, hmm. I don't know why people think that. There isn't really much difference between a Bravo 1 & 2, the main one being the 2's ability to swing a larger diameter prop. The original intended application for the drive was large heavy cruisers. Infact in the States this drive is often fitted to 28-35' sportscruisers with single or twin petrol V8's.

JW,
you can get spacers for both Bravo & DPX drives, allowing you to vary the X height. The only problem is you have to start with a high drive height and space it down. I don't know much about the Volvo ones, other than I've seen them used on several Sunseeker's, whilst I do have some for Bravo's and have experimented with them myself.
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Old 09 February 2003, 08:12   #58
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Based on the imformation here we have a good chance of having the right drive DPG for our intended use.Its obvious after speaking to volvo that they would not recommend the DPX drive for our application and predicted use and speed.If it also doesnt fit the transome shield then Im know re inventa so that puts the lid on that idea.It is a good drive and for the right application I would personaly run with a DPX in preference to a Bravo.

As far as getting a spare goes it is something we have considered as it will be taken into stock,for the long term and if we end up somewhere we cant get a spare then we can ship it out,should we need it.At todays cost,not at 5yrs time costs.

Im not sure about the main difference in the main being Bravo 1/2 is that you can swing a larger prop only.There are other differences i.e Below the waterline casing sizes and substantial drag.If your saying thats about all there is with regards to significant differences between Bravo 1/2 ,eg no heavy duty bearings or gearing sizes ,then seeing as I dont own one ,I will take your word for it.

Not sure what this spacing thing is,can you explain?Is it important on a cruising rib weighing 3.5 ton? or are we talking about setting the leg height for the optimum performance in sea trials.?Which will be taken care of bye the Builders at the time of commisioning. Or is it something else that needs doing on a regular basis,or for different expected conditions?
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Old 13 February 2003, 18:58   #59
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Dirk & CrazyH

I looked into the spacers for the DP series of drives. For the DPG and the DPX there are spacers of 1" (There're listed in inches rather than millimeters). No other sizes are supplied. For the other DP drives they are available in both 1" & 4" thickness. But, the 4" is not to be used on the KAD 42, 43, 44 or 300's. Increases the leverage on the transom plate to unacceptable levels, the Volvo man said.
The kit includes: replacement seals, a spacer plate, a stub splined shaft, an internally splined coupling and longer cap screws.

Moving on. The transom template for the DPX has the drive mounted fairly high and there is a comment about higher mounting possibly damaging the props. I'm not sure what this damage may be. A ventilating prop producing enough turbulence to cause a cavitating situation is the only thing I can think of, but it seems unlikely. Any clues on this Dirk? I'll need to take care to get the height about right since there is only the option of spacing it down by 1". It's interesting that the man at Volvo suggested an anti-ventilation plate height of 25mm below the hull at the transom. High performance normally has the plate up above the hull bottom and, indeed, the template with the DPX has the plate up about 40mm. One need's to take care that the folk who give advise are familiar with the situation in question. It would seem that he is not.
JW.
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Old 13 February 2003, 19:37   #60
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JW

Been doing some homework on the DPX and DPG and the KAD300,

There is no contest at the present time IMHO that these engines are the way to go, with these respective drives,if you got the weight advantage then go DPX if your a heavy lump then its DPG.

The Kad is quieter than the Yanmar and passes the RCD Future proposed standardes for noise output,it will burn on full tilt a measly 59ltrs an hour,and will diagnose those problems and shut down the revs before you have a problem.They are both improvements on the established respected DPE drive in that the top knuckle joint has been increased to take more power.The output at the prop is very efficient.It is faster from a standared start cos the fuel is kept at a controlled temperature therfore giving more power for less fuel burn.

The torque curve goes from around 1500 revs ,so no turbo shoot as it is more controlled and works better down below so is easier to control in a big sea.

Its to soon to say on realiability but we pitched our money on the right engine and drives I think.

People will say OOH what about Electronicks as you aint got them on a Yanmar/Yamaha, yes that is true but when Yanmar/yamaha sell there existing stock, they will in my opinion go Electronic. If they are instaled properly then I dont see it as much of a problem.

In My Humbe Opinion I am recomending to anybody who is buying a new diesl engine for a Offshore RIB look real hard at the KAD300 Before you go elswhere as on paper it is the way to go for the present time.

JW on the spacer thingy will that be sorted at time of engine instalation in and then left at the optimum position for the life of the boat?

PS If I was looking new Diesel around 260hp I think I would go same drives DPX for light boat and DPG fo heavey as the less hp will maybe make these drives even more reliable.IMHO

The one thing to be carefull of on a smaller rib less than 8mtrs in length is freeboard,if it to be used for recreational use and you feel you want to conform to rcd fro leasure boats.

The weight of these engines can make it almost impossible for a less than 8mtr rib it to have the stipulated freeboard requirment of aprox 3.5 inches in height for them to comply with rcd cat B certification at a later date.

The freeboard is measured from the waterline to the cocpit sole height/floor.Not the top of the tube,So be carfull out there.
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