Diesel v Petrol (AGAIN!)

[Mike C]

OK, so with all the talk about diesel inboard engines versus petrol outboards on this forum, plus Tony Lee-Elliot's comments in 'you know what' mag this month, we've all come to a decision about which we prefer.

I am now quite convinced that a diesel engine will be cheaper to run and go on forever.... BUT!

Does anyone have any experience of the reliability of the Stern Drives attached to them? These seem to require more servicing than the engine... and are they really tough enough for RIBS?

Anybody got any words of advice, particularly regarding the Alpha Stern Drive attached to the Mercruiser 1.7.... and does that engine really only drink 8 to 10 litres per hour at cruise?

Yours,
Perplexed of Iver

[Brian]

Mike
There is a previous thread on this forum entitled
MerCruiser D1.7L TDI
I could not believe the fuel consumption either, but read this thread for a lot more good info.

[Alan]

and this is where I come out! (and I stress that these are the arguments as they apply to me not to anyone else. I offer them for comment on my thought processes such as they are and that they might interest anyone else!)

First question - Can you afford the purchase price?

Diesel boats have a price premium over petrol boats. Example I have is 6.3 Humber with 140 Suzuki 4 stroke - 17k (basic spec 1 man console + trailer) vs £22k for the same boat with the 1.7 Mercruiser diesel. Data from Humbers own spec sheet or my recall of it! Similar or larger differentials probably exist on whatever boat you buy - Ribcraft, Scorpion etc etc.

Putting aside the running cost issue for a sec. Do you have the wherewithal to afford a diesel boat? That may be not just do you have a large pile of cash sitting around but can you afford the requisite loans, mortgage or selling the kids for medical research!
If you can (you lucky chap) then the argument essential goes down to the fundamental - low tax diesel @ 30p p l vs fully taxed petrol @ 74p+ (£1 in a marina) p l. A relatively easy calculation of number of hours you will use it vs fuel savings will tell you whether its a good deal or not. Point I would bear in mind is that a cheaper to run boat (per hour) may well encourage more frequent useage! The flip side is that there are only so many weekends in a year!

Where life gets a bit more complicated front is if you try and rationalise a larger loan say on reduced annual costs. (i.e. it may cost me another £x per month for the loan but I will save £y per month in running costs.) Its about this point I either get scared about the size of a the loan or work out that I really can't afford any kind of boat and end up in a sulk! (Or get nervous that the EU will force the imposition of full tax on marine diesel and the benefit will fly out of the window the day after I buy a diesel RIB!)

So thats the money issue. The other is inboard/outdrive vs outboard. Pro's for outboards are "designed for the environment they are in", easy(ier) to service, take up less room etc etc. Cons are of course the fuel consumption and availability of fuel afloat. Inboard/Outdrive Diesel - pro - fuel consumption, torque much improved availability of fuel & entertaining turbo whistle!. Cons - takes up lots of room in the boat, not so easy to service, maybe not designed for the environment its in (the mercruiser 1.7 being a vauxhall Astra diesel iirc) and increased servicing costs. And outdrives are expensive things when they go wrong I think that much is pretty clear!

So to go back to your original questions Mike, no personal experience of the Mercruiser (but there is a chap who posts here who has one in a 7m humber I think.). I do have some data from Humber that is pretty impressive which I can fax to you if you are interested.

Would I buy a diesel? Yes if I was in the market for a "Twister" or similar. (8.75 Scorpion / Yanmar 300) but until my lottery numbers come up I'm not. Would I buy a smaller diesel RIB vs a petrol........................................the honest answer is Dunno but thinking about it!

Alan W

[Charles]

As in computers, and much else in this world, the APPLICATION surely is one of the most important aspects of this debate. Long range cruising where you end up miles from your port or marina, where the type of fuel available is important is a very strong argument for diesel inboards. If, however, you are a Ribster who zooms around fishing, skiing and other general boating activities, close to your neighbourhood petrol bowser, then surely this would impact on your decision. For the sake of continuing this interesting subject, let me sketch a predicament I find myself in: I have a Fairline Targa which is about 34ft LOA. It is powered by two Volvo Penta 4.3l GI/DP 205hp petrol engines. Brand new, this boat will set you back approximately £109,000.00. Add approximately 18K to this for the diesel option. The boat is currently on the market for around £68K. The same boat with the same spec and vintage as mine sells for about £92K. The argument I am using is that for roughly £24,000.00, how far can you go with this amount of petrol? In 3/4 years you would be opting for a slightly larger Targa (or whatever else) and you have effectively saved a bundle. This argument is is extremely well thought out in the latest MBY (Motor Boat and Yachting). If you are keen on analysing this any further do yourself a favour and go to your nearset newstand and get this months copy.
PS anyone want a Fairline Targa so I can order my new RIB?

[Alan]

the whole equation changes if you live in the Channel Islands where petrol is 50% the price of the mainland!!

The solution to your Ribbing needs is easy ..... Scorpion 8.75m with a 500hp petrol engine

[Charles]

You are dead right!!
Now, about that Targa Alan......

[Alan]

I'd be delighted to buy your Targa off you but would refer you to my comments about my lottery numbers needing to come up!! (in which case I'd buy the Techno 40 RIB on the for sale pages )

Alan

PS Are you coming to Cardiff by Fairline then?

[Charles]

Cannot find a trailer big enough, Alan!

[Alan]

you'd be coming by sea!!

[matiboy]

coming 2007 I heard ? That's the date I believe the UK has obtained a ' stay of execution ' from the EU.

If it does come imagine the effect it will have on the boating industry......

[GraemeCooper]

So Mike

Either pull your finger out, get that diesel boat on the water and get the miles in now,

or save the cash outlay, get a good 4 stroke on the blunt end

and also save the money on ear plugs!

[jools]

OK - just to throw a spanner in the works

What about other fuels - OK a steam powered rib probably isn't a good idea, but I've seen an increase in Marine LPG being pushed at boat shows. At the LBS they even had a converted outboard

Conversion would be about £2500 per engine but marine LPG is about 32p/l as opposed to 70p - £1 /l you can do your maths.

Again as with the Diesel comments I'm not sure the extra cost for the engine would make sence for a "day" boat - but for Stealth's monster it might be an idea!! - He would have to go to Gernsey to refuel though!!

Anyway...... Here's the website http://www.lpg-boats.co.uk/

BTW as mentioned on another thread my Freelander V6 has been converted to LPG - I reckon that in the first year I will have saved the cost of conversion - and after that I will be saving £2000+ a year on fuel costs. - I don't have a company fuel card

[Alan]

a RIB lpg conversion has long been intriguing me. Up til now my think has been - need to find a RIB with an inboard petrol (rare) and convert. Not impossible but not so easy. But if someone is really doing 4 stroke outboards that a whole different kettle of worms (to mix my metaphors!). I know honda were looking at it a couple of years ago but had heard nothing more.

Other big question I guess is where to put the LPG tank? Assume that it couldn't go under the floor as per the petrol tank on a RIB as it needs to be able to vent to the air. But may well be wrong.

LPG availability isn't a problem on the East Coast or South Coast.
Hmmmmmmm better check out that website!

Alan

[Mike C]

Mmmmmmmmmm, Thanks guys. I take your point about the extra costs. At £18,000 difference I wouldn’t even consider the diesel option, but at the £4,000 extra, and that's about the difference Humber quoted me too, (Still waiting for Ribcraft to get things together - evening Mark & Jason!), it may well be worth considering. OK, £4,000 is a lot of money to use on petrol but then that equation only works if you throw the boat away when you've finished with it. Presumably a diesel boat should have a higher re-sale value, so all the £4,000 won't go! Availability is a big issue, (which is what puts me off LPG..... (and the pressurised tank!). My main worry at the moment is the reliability of the outdrive, (and that applies to petrol inboards too). Still like the idea of cheap cross channel trips! Anyone want to buy my current Ribcraft 5.85? Then I will really have to get down to the decision making!

[Charles]

Ok, Mike...let's do a swap, I'll give you my Targa and in return you give me your Ribcraft plus 60K.. deal?

[Jono Garton]

Is the 60k the for delivery costs ie petrol?

[Mike C]

Stealth,

Yeah, great idea. Trouble is, it wouldn't fit in the front garden. I get enough stick from the wife about the RIB being there as it is Maybe if you find someone else to buy your Targa, they could buy my RIB as a tender? I'd never launch it down the Dover slip either!

Mike C

[Alan]

I mailed LPG Marine & asked them about LPG conversions for outboards and where tanks could/should be located.

Response was.........

1. We have converted a 100hp 4 stroke to dual fuel, a quadruple carb set up. Development of this concept is in its early stages, so the kit is all hand built, CNC'ed etc and the craft must still comply to the COP 18, LPGA regulations. The kit to build by hand as you would expect is quite expensivei.e. £2,000.00. We are looking to go into the EFi market as this is where the manufactures are going.

2. LPG tanks can be mounted under the cockpit, seats or under the decking. All the tanks need to be fixed into place as a permanent fixture and all need the be vented via a skin fitting over the side / rear of the boat.

The rib would required all the safety systems, fittings, fitted under
the LPGA's code of practice 18. You may look at putting an inboard in, if that is an option! That has been done by us.

Interesting stuff eh!

[Mike C]

Did they mention if you need a left-handed gerzerbalsplat or the new ambidextrous fitting. Also, I hear tell that the rear venting can be omitted with the use of an oral inhaler, (obviously to ISO spec 7864679076580, sub section D, paragraph 4). The technique is to fit the inhaler into the LPG tank, ensuring that the attached tube is fed under the pod seat, through the cushion and up your arse.

Seriously, I was under the influence, sorry impression, that LPG needed to be stored in a pressurised tank. That does not sound very healthy to me in a RIB! Also, I have yet to see any figures that tell me how far you can go on a litre of LPG. OK, it’s cheaper per litre but is it as efficient? If it only takes you half the distance????

Maybe the best idea is to use that oral inhaler after attaching as described above, connect the other end to the engine and eat a lot of beans!

[Alan]

the LPG marine people respond to emails. Whereas RIB Manufacturers and brokerage services with websites seem somewhat reluctant to do so