Petrol v. Diesel

Chris Murray · 24 May 2005, 00:01

I know that diesel is likely to go up to something approaching road prices but my 3 litre diesel car goes a jolly site further on a gallon of diesel than an equivalent car running petrol. Typically, its about 26 mpg diesel and I believe it is something like 17mpg petrol. It weighs about 2.25 tonnes.

With this in mind, has anyone experience of the MPG for a 240hp diesel Yamaha in an 8mtr or 8.5mtr boat? What is the performance like?

I would consider the 315 Yanmar (as opposed to Yamaha) but I understand that the Bravo 3's that they mate them with keep falling apart. Actually, an MPG for this would be good too. Just in case they find a sterndrive that works reliably with it!

Cheers!

Chris.

craig_c · 24 May 2005, 10:42

Hi, ive got the yamaha 165hp diesal in my 7.4 redbay and it does around 300miles for £60. it weighs 2 tons so i think thats pretty economical

JIY · 24 May 2005, 11:01

Hi Chris,

I've got the 250hp Yanmar coupled to the Bravo3X leg on my 8.5m Tornado. Fully fuelled (200 litres) and four on board, it weighs in at a little over 2 tonnes. I work my fuel calculations on 1 litre/nautical mile - that allows for rough water and some tacking round larger waves.

My usual consumption in reasonable conditions (wind force 3/4 or less over a large fetch) is about 5.5 gallons/hour cruising at 32 knots (thats at 3000 revs - max revs are 3700 which gives 42 knots, but burns about 7.5 gph).

I chose the 250 Yanmar, because it gave me the smooth 6 cylinder engine (the 240 is 4 cylinder), without going for the 300hp (now 315hp), which anecdotally seemed to be breaking the Bravo3 legs.

Hope this is useful info.

Jim

Alan · 24 May 2005, 12:51

Louise is clearly sleeping on the job so I will do this on her behalf

http://www.rib.net/forum/showthread.php?t=8996

Chris Murray · 27 May 2005, 18:29

Thanks everyone for your input.

One issue I read about somewhere (might have been the RYA site) is that when red diesel eventually goes, whether 31/12/06 or later, there could be a problem getting ordinary diesel alongside.

Worse, until the price changes, diesel engines are being sold at a premium in the UK. This means that I could pay over the odds for an engine, and then a year later find fuel difficult to locate. Mind you, as I shall be towing, I guess that this should not be too much of a problem.

If I knew that I could get red for say 5 more years, then I would have to seriously consider this type of engine. However, there doesn't seem much to choose from at the moment, with Yanmar routinely breaking Bravo 3 legs and no other suitable engine/drive option without buying Volvo, which probably work more reliably but are even more expensive!

Regards,

Chris.

Richard B · 27 May 2005, 19:41

The bigger problem with the Yanmar 300/315 24-valve engine is not the Bravo leg failures, but the engine block failure where one of the engine mounts is close to an internal oil gallery. Barrus themselves are confused about their own supplied modifications, but all the different "braces" which are supplied are a workaround rather than cure. I'm told that Mark Pascoe had a proper solution which involved re-locating some of the externally mounted components so that the engine mount could be fitted in the same position as the Yamaha 240 12-valve engine, which doesn't suffer from this problem.

If you're interested in a Volvo engined RIB, Paul Lemmer is brokering a superb 2-yr old Ocean 8.5m powered by a 300hp KAD42 duoprop, full electronics, radar, trailer, £45,000

gavin · 27 May 2005, 19:57

I dont drust diesel outdrives, unless they are Yamaha, Bravo failures are far too common, I respect not to the extent with 240hp, and we all agree its torque not hp, that kill them, but out at sea you must have reliability, ifts not Hydra drive its too risky.

jwalker · 27 May 2005, 20:07

Quote:

Originally Posted by Richard B

....If you're interested in a Volvo engined RIB, Paul Lemmer is brokering a superb 2-yr old Ocean 8.5m powered by a 300hp KAD42 duoprop, full electronics, radar, trailer, £45,000

Yeh, I noticed that too. Pity a KAD42 doesn't give anything like 300hp.

Richard B · 27 May 2005, 20:08

What's their output?

jwalker · 27 May 2005, 20:08

Quote:

Originally Posted by gavin

.... ifts not Hydra drive its too risky.

You can't 'arf talk some pish, Gav.

Richard B · 27 May 2005, 20:10

Quote:

Originally Posted by jwalker

You can't 'arf talk some pish, Gav.

You can't talk to Gavin like that... the same bloke measured our boats, I'll have you know!

jwalker · 27 May 2005, 20:10

Quote:

Originally Posted by Richard B

What's their output?

Not dead sure but, from memory, about 200ish at the prop.

I've a feeling Volvo only now do the 41 & 43 in the 40 series but that may just be my flaky brain.

Richard B · 27 May 2005, 20:10

That's a bit different!

Richard B · 27 May 2005, 20:12

googled it, Fairline seem to reckon about 230hp?

jwalker · 27 May 2005, 20:16

Quote:

Originally Posted by Richard B

googled it, Fairline seem to reckon about 230hp?

Yeh, that's about right but it'll be the crank power. Volvo drives use up about 12-15hp.

Edit: Just pinched this from Volvo.

.....................prop ....crank ...rpm ...cyls ...capacity
AD41P/DP ......189 ......200 ....3800 ...6 ......3.6
KAD43P/DP .....218 .....230 ....3900 ...6 ......3.6
KAD300/DP-G ..272 .....285 ....3800 ...6 ......3.6

Edit,Edit; WTF! it wus all nicely in line when I wrote it....I think. Typical PC, I thinks it knows best. Anyway, me dots have tricked it.

Richard B · 27 May 2005, 20:19

Don't panic, Volvo's website mostly agrees with yer perfectly functional brain!

Rogue Wave · 27 May 2005, 20:25

It all depends on what you want!. If you want to cruise for long distances and have a smelly dirty noisy engine that runs on stuff that costs thirty pence a litre then it's gotta be diesel.

If you are looking for a speed fix then it's gotta be petrol.

You could consider having twin mercuser 120's or the VW 150's if you want diesel although the Yamaha is a very good lump. re drive's do the company sterndrive do something suitable for the Yamaha lump

gavin · 28 May 2005, 17:37

In Dublin a company operates Ribcrafts as passenger carring ribs, out into the bay for trips etc.They all run diesel outdrives , they are constantly replacing Bravo outrive units, constantly, we see some ribs with Yamaha hydra drive units, I dont hear any problems about them, these are virtually the only outdrives fitted by Redbay boats for example.I only know of one other boat apart from Jwalkers that run Volvo, In Ireland Volvo parts are very expensive, I never like the idea of a rubber bellows which if perished can lead to water flooding the engine bay, I also know it works and must be replaced or inspected periodically, I often wonder why Volvos arnt popular in Ireland, on Ribs, again I think mostly due to cost, spares etc.
I have heard nothing but positve feedback about Yamahas, I know you can do the searches and read how many were used by Alan Priddy, going around the world .Even with transom showers fitted, Bravos are failing, it gives me no confidence in them atall.With outdrives you can never trim them fully out, with boats on a mooring etc, this obviously causes more maintaince issues, anodes, as I mentioned bellows perishing, growth and weed fouling etc.
Diesel units are more expensive to start off with, if you get the hours up, it becomes viable to run diesel, and it may be an economical choice for the user.However with the problems we constantly see with Bravos, I would never fit one, I would also have to say I would have a lot more confidence in Volvo, but they are expensive units to buy.
I have always been impressed by Yamaha, motorcycles, outboards, and I like the Hydra drive concept.
I definately feel they recieve the best reviews, there has to be good reason for this, its the only outdrive I would fit, and if Volvo are a serious market leader, why arnt they on more ribs.

Solent Ranger · 29 May 2005, 07:19

Quote:

Originally Posted by Rogue Wave

if you want diesel although the Yamaha is a very good lump. re drive's do the company sterndrive do something suitable for the Yamaha lump

I have a Yamaha 370 sti in my boat. Outstanding 4 cylinder diesel that does not smoke or smell. The unit comes complete with sterndrive. A sterndrive that takes some beating! Silky smooth - no clunking and grinding like you get with Mercs or Volvo sterndrives. I love it! Best peopel to contact are MMS at Eastlands Boat Yard in Swanick & speak to Bill Brown.

tonka · 29 May 2005, 18:37

i have 2 240 hp yamahas with hydra drives they burn about 7 gallons a side cruising at about 28 knots good engines and drives only prob is having to service legs every 100 hours apart from that id pick it before yanmar with bravo leg, used too have volvo kad 42 with 290 dp leg was great engine and leg it was about 8 gallons an hour at 30 knots,