That old chestnut again!

pettal · 01 July 2005, 09:34

Hi all,

I know this has probably been answered before but as I hadn't heard anything for a while I wondered whether there had been any technological advance in marine diesel engines.......more importantly size and weight.

I notice XS-Ribs are going to start doing a 7.5m, 8.5m and 9.5m range and it got me thinking about what the best size diesel engine for a 9.5m rib would be.....based on cruising at 35knts(ish).

I'm looking for a lightweight engine or something that can at least compare with a twin outboard installation on weight and power.

What do people reckon is this realistic or how close can I get??

Jono · 01 July 2005, 09:46

Yer just too late........

pettal · 01 July 2005, 09:59

Nice!

All we need now is the freighter it came out of and stick some toobs on it!

Andy Gee · 01 July 2005, 12:03

I personally would go for the Yamaha. Its robust, reliable and good value. I think they are now putting out about 260-280hp, which gives it good PtW ratio.
The largest buyer of these engines in the UK is the Army/Navy for the new rigid raider I think, then of course Redbay

. The other option is this Rolls Royce V12 with only 42hrs, c/w free 500Kva Geni

All in my humble opinion of course

Andy

ps see Redbays new website at www.redbayboats.com

pettal · 01 July 2005, 12:06

Thanks Andy!

Anyone have an idea of prices for these or where I can get hold of a price list?? I seem to remember that Yamaha don't publish their prices on the internet which is a little unhelpful, but if anyone can get me a price it would be very much appreciated.

Ta

P

Andy Gee · 01 July 2005, 12:11

Try Bill Brown at BBMS 01489580250. I have allways found him to be very helpfull, in fact now I order any spares direct from him as he seems to be the only Yamie dealer that keeps anything for the inboards in stock

.
Andy

pettal · 01 July 2005, 12:17

Thanks Andy!

Daniel · 01 July 2005, 13:51

Would you be so kind as to report your findings RE pricing back here so "onlookers" like me can get an idea. Thanks.

pettal · 01 July 2005, 15:54

For the on-lookers:

Price for the ME421 STi works out at around £14,500 +VAT and kicks out 243hp @ 3800RPM

Now that's pretty good considering a new Verado is approx £16-18k (inc vat) so why is it that as soon as you mention sticking a diesel into a rib does the price suddenly rocket!?

Surely it's not £5k's worth of more difficult sticking a diesel engine and stern drive into a rib than it is chucking an outboard on the back!?

Jono · 01 July 2005, 15:58

Quote:

Originally Posted by pettal

Surely it's not £5k's worth of more difficult sticking a diesel engine and stern drive into a rib than it is chucking an outboard on the back!?

Perhaps they charge by the Lbs............

Scary Des · 01 July 2005, 16:27

Look at this Might be interesting

Des

JIY · 01 July 2005, 17:02

Hi Pettal,

The problem with diesels will always be the engine legs - Yanmars are great engines but the Mercruiser Bravo legs (their standard counterpart) can certainly be troublesome.

I went for the 250hp Yanmar coupled to the Bravo 3X leg, because at the time (late 2002) the 300hp Yanmars appeared to be blowing even the 3X legs. The leg has now done 330 trouble-free hours. The engine and transom installation have completed 620 hours. The leg was replaced at 290 hours because I discovered that Barrus hadn't given Barnet Marine the 3X leg - I had the "bog-standard" 3 installed. (By the way, Laurence Lock was most attentive in resolving this problem, as ever). The steering pin in the helmet now needs replacing (the helmet has completed 620 hours), but apparently that is fairly common in RIB/diesel installations.

There are huge advantages to diesel - availability, price, economy, safety etc. But there are some downsides - servicing is more expensive (leg every 100 hours, engine every 120 hours, about £500 inc VAT in total). And you don't get the same accelaration "off the mark", although once you are in the turbo range (about 18 knts+) throttle response is pretty rapid. You also need a reasonable waterline length to offset the weight of the diesel engine, but I'm sure Laurence will have already given you good advice about this. He was the one that talked me into the Tornado 8.5 and I have to say it performs even better than he suggested. The rough water handling isn't limited by the boat, only my fear!

I'm not sure about the reliability of the new Volvos yet (D3/D6 etc) - Jeff Walker would probably be able to give good advice on the D6.

Waterjet drives seem to be more reliable, but the handling in rough water can be compromised.

I know that there were problems with the early Yamaha Hydradrives (search previous threads on this forum), but Tom MacLaughlin (Redbay boats) says that he wouldn't fit anything else, so I guess that speaks loads.

Good luck with your decision - I can assure you that it's a minefield and one that I've walked every inch of!

codprawn · 01 July 2005, 19:43

http://boatdiesel.com/index.cfm?S=DM...EYR&Engine=256

Have a look at this - brilliant site with spec on most engines - saves going to all the different makers sites!!!

Brambles · 01 July 2005, 20:27

As always, this is a very interesting debate. I wonder weather it really boils down to factors other than money at the end of the day?

For example a large rib encourages longer passages, which means the availability of fuel at ports becomes more important. You can always get diesel but petrol? Forget it even at some large ports such as Weymouth.

Also, I am informed, that a diesel rib runs “flatter” in the water than an outboard equivalent. Effectively it goes through most of the waves rather than flying over them, and therefore provides a more comfortable ride?

As a counterpoint however, I heard an interesting conversation at Ribex recently, between a customer and a manufacturer. The guy already has a 10m cruiser with twin Yanmars, but is considering outboard petrol units for his soon to be ordered new cruiser, because of the uncertainty over fuel duty and the increased cost of buying, installing and servicing the diesel units.

Finally, I have always wondered about surface drives. It seems to me that the problem with inboard legs is the number of joints in the legs and the amount of power being transmitted through them. So why aren’t surface drives more common? Is it cost, steering problems, or perhaps trimming issues in rough water?

Any thoughts on this?

Regards.

Ian.

Andy Gee · 02 July 2005, 10:26

Quote:

Originally Posted by pettal

For the on-lookers:
Surely it's not £5k's worth of more difficult sticking a diesel engine and stern drive into a rib than it is chucking an outboard on the back!?

If you were to cost out things like engine bearers, engine covers etc etc that would be about right.
Andy

pettal · 05 July 2005, 14:21

Thanks for all your comments/help/suggestions!

I'm still not 100% on going either way as you've all said there are up's and downs to both.

I'll have to sit doen and work out exactly how much fuel etc I'm using as I seem to be filling up the 170ltr tank every other week and although Guernsey is roughly half the price of UK petrol it still stings a bit.

On another point I'm suprised at the amount of servicing the legs need. I had another boat that had a bravo leg on it which got used every week. The boat got serviced once a year with no problems!?!? Am I just lucky???