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Old 01 May 2004, 07:39   #1
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Yanmars

I have been raking over the coals of the cheap yanmars thread below,

http://www.rib.net/forum/showthread.php?t=4324

I am still puzzled over some items. If yanmars suffer from cracked blocks, and the yanmar block is the same as the yamaha block, which is the same as the toyota landcruiser. Then why dont yamaha suffer the same problem?
Also, I have heard no bad comments about the yamaha leg. Is it better than the bravo's? Can it be bought separately?
I must admit the bravo legs seem a real liability. I dont know how much warning you get before it fails completely, or if it is a sudden failure.
Its a shame there is not more choice in this area.
Nick.
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Old 01 May 2004, 14:09   #2
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From what I can gather it is more the application that causes the problem - a Yanmar in a Sunseeker has a much easier life than in a Rib - also the Yamaha units are lower hp so don't stress the drives as much - but I am NOT speaking from experience so take with a pinch of salt!
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Old 01 May 2004, 15:01   #3
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Nick,

I just spoke with another Yanmar owner who's suffered a cracked block this week. He's done some investigation into the problem and found that they all(?) crack in the same place - near an engine mounting. The mounting in question uses three bolts, whereas the mounting on the other side uses four bolts. Also, he tell's me that there are internal oil colling galleries running close to this point. Apparently four bolts could have been used, but Yanmar have mounted some of the external components close by. I don't know if Yamaha do the same. He also tells me that builders such as Mark Pasco move these components and modify the mounting.

Yamaha drive legs do go - just read Alan Priddy's book to find out how many he broke going around the world. Also leisure users have suffered drive failures. Jim Mackintosh (BIBOA secretary) would be a good source of information.

All 2nd hand info, but HTH.
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Old 01 May 2004, 16:51   #4
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Alan Priddy

To be fair Alan got excellent life from his outdrives at least one of his problems were collision related, look at the mileage he done, its not a fair comparrison
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Old 01 May 2004, 17:51   #5
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What's not a fair comparrison, Gavin? If you read Alan's book you'll be able to work out the MTBF for the outdrive legs. You'll also be able to find out Alan's analysis for the reason of the failures. You could also ring up Jim and I'm sure he'd be happy to give you his view on the situation from a leisure point of view as well.

The Yamaha Hydradrive is very nicely engineered, but if you think it's perfect, then you're looking through either rose tinted glasses or beer goggles!
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Old 02 May 2004, 04:25   #6
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What's not a fair comparrison, Gavin? If you read Alan's book you'll be able to work out the MTBF for the outdrive legs. You'll also be able to find out Alan's analysis for the reason of the failures. You could also ring up Jim and I'm sure he'd be happy to give you his view on the situation from a leisure point of view as well.

The Yamaha Hydradrive is very nicely engineered, but if you think it's perfect, then you're looking through either rose tinted glasses or beer goggles!
I like Hydradrive legs as they are very smooth. I can't comment on the reliability however.

The Yanmar/Yamaha block is Toyota Landcruiser 4.2 block. In it's road form it produces around 130 hp The Yamaha engine produces around 240/280 and the Yanmar in excess of 300hp. I personally believe this might have something to do with engine reliability. If the engine is light and has a high horsepower then it'd likely to be low on torque. If you put it into a high torque application like pushing a big cabin cruiser ...wouldn't that cause a problem ?

re legs my understanding is that Mark Wildey has a Bravo three with a shower attachment and I think that's worked well for a while? I don't think Hydradrives can handle much power over 280.
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Old 02 May 2004, 04:42   #7
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Interesting discussion, given that I'm awaiting repair of my Bravo 3 (see Bravo 3 thread).

Does anyone have info on the reliability of Volvo engines and legs? Perhaps the new D3s will offer more in terms of reliability on RIBs?
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Old 02 May 2004, 04:47   #8
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Toyota Landcruiser 4.2 block. In it's road form it produces around 130 hp
Bit more, actually Stuart. The 4.2 does 201hp, (the 4.7 v8 does 235hp).
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Old 02 May 2004, 05:26   #9
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It's the D6 you'd need, Jim. The 300hp one. It looks good but it weighs 380lbs more that the KAD 300. There's always a catch.
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Old 02 May 2004, 16:08   #10
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Bit more, actually Stuart. The 4.2 does 201hp, (the 4.7 v8 does 235hp).


Did you know that or look it up?
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Old 02 May 2004, 17:00   #11
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I had to look it up of course! I'm not full of that much useless information. I thought 130 was a bit low, so checked it out...
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Old 03 May 2004, 09:51   #12
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Thanks for the replies chaps, I am a bit clearer about this issue.
As Jim asks, what about volvo legs? are they better?
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Old 03 May 2004, 14:39   #13
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Yamahas

Yes Yamahas do go, however you cant make a comparison bassed on a round the world trip with a Yamaha outdrive, pushing a boat loaded with, was it 4 tonnes of Diesel, Alan used 3 outdrives, to be fair one failure was the result of a collision with an unmarked fish farm,it may have done it on two outdrives apart from that incident.Look at the variables involved, fuel quality not always as good as it should be, invaribly you have to run the motor harder to get the preformance, huge fuel weight and heavy boat, long periods at sea, endless running time, the paint on the top of the hydra drives melted with the heat, these were extreme circumstances, I would be quite happy to use two or three on a round the world trip.I definatley like the concept of the hydraulic drive system and I do hear of much more Bravo failures than Yamaha ones.No Yamaha drives arnt infalible, however when you see aftermarket modifications to reduce heat on outdrive units ie showers, you have to wonder

quote

The Bravo 3x drive, well, well, well, after 800 hours and 3 legs I decided it was time to sell the boat, the leg and engine (300 hp yanmar )was serviced as required by the manufacturers, I have just heard that the 3rd leg has now got problems.......thank god its not mine anymore....installing Yamahas in the new 11m, wish me luck!
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Old 03 May 2004, 17:10   #14
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Quote:
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...installing Yamahas in the new 11m, wish me luck!
To which drives, Gav?
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Old 04 May 2004, 11:43   #15
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drives

Not sure which drives he is going to fit,
http://www.rib.net/forum/showthread.php?t=4725&page=2
Have you had any bother with the volvo drives
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Old 04 May 2004, 12:10   #16
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Rouge Wave

You are correct that I have the shower unit fitted. I think this piece of equipment is a must for all outdrives. Use the search facility on RibNet and look for old posts as I seem to remember a thread that had a URL for a US web site selling the shower for $150 ( ish ). Much cheaper than the one I had fitted !!

Cheers

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Old 04 May 2004, 15:37   #17
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Have you had any bother with the volvo drives....
None at all.

It's not been in the water yet.
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Old 04 May 2004, 15:41   #18
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Quote:
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Rouge Wave

You are correct that I have the shower unit fitted.
Agreed, quite shocked to find even the Stern Power one on my Pacific was warm after half an hour of high speed (comparatively) running and this has a separate exhaust.

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Old 05 May 2004, 16:52   #19
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Are anyone here familiar with fnm engines, lightweight diesels with saltwater cooling?

Where I live (in Norway) Yanmar is known to be one of the most reliable engines.And they are quite light in weight compared to several others.

But I will always keep a button on Cummins engines, as I think they are as reliable as anything, although they tend to be a bit on the heavy side, but cheaper than Yanmar.

Reliability I think often has a little bit to do with cubes to hp.
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Old 06 May 2004, 05:27   #20
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Cracked Blocks

I have a friend who works for a commercial RIB builder and has some experience of cracked yanmar blocks on military RIBs - apparently they don't like being thrown out of the back of aeroplanes!

Their way of reducing the incidence of block failures is to fit a substantial stainless steel saddle beneath the engine. This is bolted to the engine between the block and the engine mounts. This, apparently, reduces the twisting force that the mount puts into the block thus reducing the tendency for the mount to tear out the side of the block.

I have not seen this myself but it sounds like a good idea.

The more I hear about failed sterndrives and engine blocks the less I mind the cost of petrol for my (very reliable) outboard!

Duncan
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