Diesel good v petrol bad

[oldgit]

Ok.So let me get this straight after a visit to www.boatdiesel.com I now have got the idea that the only thing going for turbo diesels is that they are cheap to run and that is about it fitted to the average boat maybe up to 30 ish odd feet.Even then they are grief because they are not used as they should be.
They are noisy, smelly, vibrate like hell, heavy,generate vast amounts of heat and require servicing more frequently than petrol and at vastly greater cost when things go wrong
and please no comments about reliabilty or safety.The last boat fire I saw in the magazine involved a diesel boat.
So why apart from running costs have a oil burner ? when owners do what ? at most 0-200 hrs a year.
Apart from keeping pauls eng in caviar and rolls royces etc

<P ID="edit"><FONT SIZE=-1>Edited by oldgit on Sun Feb 10 20:52:04 2002 (server time).</FONT></P>

 

[coliholic]

But work out the fuel costs yourself

Kim gave some guidelines a week or so ago. Diesels consume 5 galls hr\100 HP and petrols 7 galls hr\100 HP at WOT, so the petrol uses 40% more fuel than the diesel.

Let's assume that your assumptions are right and Mr typical boat owner does 200 hours a year.

My twin diesel Mirage (2x115HP) actaully averages about 9 gallons an hour as against a petrol versions 12.6 galls\hr. So in a 200 hour year @ 30p litre it'll cost me £2,500 for diesel and the petrol version @ 75p litre would cost £8,600.

So I'm over £6K better off than a petrol boat.

Yes the diesel boat costs more to buy than the petrol, but it's worth more than a petrol boat when it comes to selling it too, so you can take that out of the equation. Though I suppose there's the loss of interest on the difference in purchase prices but with interest rates as they are I don't think that's a valid point anyway.

Am I going to spend an additional £6K a year on maintenance? And there's less to go wrong with a diesel. And how would you feel about filling up the tank? Mine holds 110 gallons so costs me about £150 to fill up. To fill same amount of petrol would be £375. Kind of spoiling a good day out? Always assuming you can find a miarina selling petrol of course.

 

[oldgit]

Crikey ever written the most wonderful reply ever to be posted ever and then watch it disappear as you are cut orf in full flow.anyway.
All details at WOT.So bit of red herring
No one ever goes anywhere for 200 hours on trot at full throttle(well maybe matts)and richard branson
Even if off to france etc in big fast boat Full throotle all way? and not slightest worry about mr volvos finest kit coming to pieces half way across.
Suspect lots of diesel boats would not know what salt water was if they were floating in it.
Therefore biggest adventure penton hook to pub at chertsy. creepy crawly speed all way.
Bet not so eco then.Just those mega bills when goes wrong.
Agree with comments about availability of petrol but what will happen when red diesel exception is withdrawn the cost advantage will narrow.

 

[coliholic]

But that's not what I said,. At WOT my total of 230HP should use according to "industry estimates" 11.5 galls hr but in reality mine averages 9, 'cos I don't run flat out all the time, hence the lower avge fuel consumption and cost. And I've used the same lower consumption basis for equivalent petrols. But there's no getting away from it, petrols use 40% more fuel for the same given output as diesels and are a heck of a lot more expensive to run.

And it's not just a question of "oh it's only a few quid". Well to me anyway an additonal £5 or £6K a year would make the difference between using the boat or not. You may be in a dfiferent position where the cost is not relevant, but I've got a sneaky feeling you're not.

So what's really behind your post? Have you seen a petrol boat you've fallen in love with and are now trying to justify it?

 

[BarryH]

I can understand what holic is saying, But 230horses from 2 engines, extra wieght mut have an effect on trim speed ect. Had some bad experiences with oil burners, mainly with fuel quality which i found varied quiet alot. To the average boater, i seen it qouted most boats only do around 50-70 hours a year, the cost difference will be negligable over the year. Still thats boating, nothings cheap in this world, and anyhow do what i do, claim it all against yer tax bill, then in reality it dos'nt coat anything, Now i'm off to fill up with £200 worht of petrol to have a quick trip round the bay.......

 

[rich]

a diesel will live a dar'n sight longer than a petrol. my last boat had 2 volvo aqd40s built 1979. never had any probs, power and torqe, cheeper to maintain than petrols JUST ADD {SOLTRON}

 

[boatone]

Re: \'Ere, \'ang on, this is getting personal....

Quote "Therefore biggest adventure penton hook to pub at chertsy" -unquote.
You're treading on my territory here and I'm not 'aving any of it, do yer hear!!!
No way can Penton Hook to pub at Chertsey (note capital letters, 'e' in Chertsey etc etc) be regarded as an adventure. Now, getting out of Bates Marina this week to get to the Pub at Chertsey..........THAT could have been a little bit of an adventure......(Old Father Thames just a little bit angry at the mo' )

TonyR
boatone@boatsontheweb.com
www.boatsonthethames.co.uk

 

[PGD]

Why does everyone slag VP diesels – there seems to be very mixed opinion here. As you may be aware I’ve just re-engineed my Fairline with a AD31P 150hp turbo diesel after loosing my V6 petrol to frost damage – there are prone to it I’m told. My decision was based on running cost / future resale value / original design of the boat. No point putting some 50 hp engine in a boat designed to do 25 - 30kts.

Anyway – it’s a bit heavier and a bit noisier so installed sound insulation and turned up the music a bit The cost inc. heating, hot water and labour and VAT was 14K, boat just valued at 18K –20K – one sold 2 years ago at that price. So I have about £5k to recoup and based on your figures and would do this in a year – I’ve said 4 years to my self.

So with that said have I done the wrong thing, petrol B*** expensive up my end of the Thames nearly £1.00 a litre and disappearing fast, diesel about 26p at Shepperton. True the turbo doesn’t get much use so I try to kick it in when turning around in a weir pool.

So is this new engine about to fall apart when I go salt water ?

Peter

 

[tcm]

don't think everyone does slag vp engines- but since they have so much of the market, the qty of moans is large, but it could be (relatively) small?

 

[PGD]

True people only complain and hardly ever compliment.

Sounds like one of these government statistics things, for example that Jags have less accidents than minis – thats cos there aren’t as many jags on the road !! )

 

[Guest]

Re: Diesel Mirage

Interesting you have a twin diesel Mirage. I had a 1984 Mirage (one of the last built I think) from 87 to about 91. She had twin AQ 125hp petrols and apart from the lack of waterside petrol on the Clyde and having to refuel via 5 gal cans, the performance of the boat was bit wanting. One or two up, I could get about 21 knts flat out but she had a hump speed of about 14knts and if I had more than half a dozen people on board it could be difficult to get her up on the plane. I fitted elltrim tabs and that improve things a fair bit, but basically I always felt the boat was under powered and the more common AQ145's installation would have been better.

So basic question - what sort of diesels do you have and what sort of performance do you get?

I liked the layout of the Mirage and she was a practical family boat (my kids were kids at the time) but she was very prone to slamming and would do so in anything above the slightest ripple and often this necessitated coming home at displacement speeds for the sake of comfort and not feeling she was imminently going to break up.

Nick

 

[mtb]

Diesel for me please ,
I deal in carburetters so am aware of the maintenance required .Example once you get wear in a throttle spindle your carburetter will use ever increasing amounts of fuel ,and as for the diaphragms.
If I ever get a boat that has a petrol lump in then out it goes straight away.
Diesel engines used on road vehicles go for well in excess of 100 k and as long as you change the oil / filters on a regular basis then you should have a lot more life from them.
Injector service at 100k
Carburetter service at 35k ,
plus the ignition system to constantly worry about .
Agreed the latest petrol fuel injection and fuel management systems are far superior to carburetters.Diesel to have improved fuel and emissions systems to comply with emissions and pollution legislation
Also and I expect a bit of stick for this, there are not many marine fitters who can adjust a modern and very complicated carburetter or fuel system,I don't deal in modern carburetters and the ones I do have ,I can tell you the adjustments are critical to both keep the tuning at it's peek and fuel economy at the right level .It's not that the engineer is incapable it's just a fine art and unless they have the correct tuning equipment and data sheets available and know how to use them ,the task gets harder .
Petrol engines do run faster but don't have the raw power like a diesel
And as for fire risk ,I'd much rather have a fire on board with a diesel tank 10 ft away as apposed to a tank full of petrol.The constant high safety risk issues with petrol compared to diesel.
Still need more convincing
RNLI all inboards are diesel harbour craft such as pilot boats tugs and so on ,diesel engines . Yesterday out on the wash it was very wet and had I had a petrol engine chances are water would have caused problems re the ignition system.Where as the diesel didn't miss a beat.
As for costs most of it has already been said but what about the actual life of a petrol engine compared to a diesel .
You will have to rebuild a petrol engine long before a diesel .
One last thing your quite right about most boats not being used apart from just a status symbol and so in those types of craft, does it matter because they rarely leave the jetty.
Mick

http://homepage.ntlworld.com/boats
I want a big steel ex trawler / tug v/cheep or swap for tug

 

[cngarrod]

Re: Diesel Mirage

Nick,

Got yourself another boat yet?

Craig.

 

[Guest]

Sorry oldgit but can,t agree with you there as I do petrol engines as well!, and I dont like caviar, think thats how you spell it.....is it matt?
One sobering thought to make you change your mind aq 171 has to have new cam belts every year as the pulleys rust and the belt snaps, also an exhaust manifold costs about a grand and they eat these, you have been warned!.

Paul js.

 

[oldgit]

Arrgh now where was that advert for that rowing boat.

 

[coliholic]

Re: Diesel Mirage

Ours is an 85 with two turbo AQAD30's (115HP each I think) and duoprops. Most we've had on board was four on the sea and we managed 23knots flat out, but that was with a nice clean freshly antifouled bottom. Cruised comfortably at 18-19 (3,000rpm) and that with a dinghy on the back too, though four adults on board and with the dinghy on it's certainly stern heavy and need to work the trim tabs.

We've got the Bennet ones and I think they're pretty good though never tried any others. When we did the cross channel last year there was just two of us on board and it was OK, getting on to the plane at about 12-14kts, but once there could drop down to about 11 before it dropped off all of a sudden, can take you bit by surprise then.

We came back from Belgium in a good F5 into wind over tide and it did slam a bit, but slowed down to displacement speed ('cos the Princess 38 we were with found it a bit too rough) and was actually then even more uncomfortable.

I think the 115's are just that bit underpowered, could really do with the 6 cylinder 41's but then don't know if the weight penalty would outweigh the advantages. We've got the soft top version and it's a nice practical boat, and even when it was rough never thought the boat couldn't take it or might break or anything. As you say well laid out inside and perfect for the river where we do most of our boating.

I suppose everyone always wants more power. Never heard anyone say, "my boat's overpowered and too fast"

 

[longjohnsilver]

Funny that.......

I've always said my boat is overpowered and too fast!! <BG>

There you go, you've heard it here first!!!

 

[oldgit]

Re:More myths ?

100k in a industrial truck/generator used day in day out yes.But found only one boat with more than 2500 hrs on clock and that was 24 years old.Most has 800-1400.ie most 100hrs per year on a well used boat, on average hours seem to be 70 hrs per year?
Ok so your oil engine will never get the chance to show what it is best at ,long life.
most fail I suspect because of lack of use or poor maintaince due to cost.
Total me up two bills for a low time but oldish engine that needs the fuel/exhaust system sorting out ie.what you will find in most pleasure craft.
a,Petrol-replacement rebuilt carb 4 or 6 spark plugs set of points/new cap and maybe new filter.replacement exhaust riser .
b,Oil burner-replacement fuel pump,injectors filters and exhaust riser
c,Work out -the different labour costs inc.time taken for both jobs to be carried out and the level and cost of wages of the skill needed by the person carring out the job.
Ooooh and I now this is a bit unfair but I want you buy the bits for the petrol job from Sierra using pattern items.This a low use fun boat but we will pay someone else to fit the stuff.I suspect that some owners could easily fit carb/plugs but diesel bits I doubt.lol.

 

[Guest]

Re: Diesel Mirage

The reason I was asking about the diesels is that they are generally heavier than the petrol equivalents and the relatively narrow stern sections of the Mirage mean that engine weight is pretty critical. I don't think therefore she would handle the weight of 41's which would be substantially more than you have at present.

Re structural integrity, I never had any real problem with mine but the interior moulding did start to part company with the hull on the port side under the forward dinette cushion. It was evidenced by quite hard to see cracks when at rest in the marina but I noticed it by chance when retrieving something whilst under way. Flexing showed it fairly clearly then and it was easily fixed by just glassing it in again. You might do well therefore, to check your own.

As I say, overall, I liked the Mirage and no one seems to make that sort of boat any more which is a pity. The Princess 32 was a similar design but, again has gone to the great design shop in the sky. If I was looking at a similar but start from scratch design, I would

a) move the engines to where the fuel tank is at present and use V drives to give a shaft driven boat. In fact it might not need V drives as the aft cabin river version of the boat had a single diesel sat exactly where I describe. My 280 outdrives left me with a pathological dislike of the whole concept of outdrives so one way or another it would have to be shafts.

b) I would reposition the fuel tanks outboard down both sides all the way to the stern. I think there is room for twin tanks of about 70-80gals each. If a holding tank was required, it could somewhere in the lazarette. ditto the calorifier
c) I would incorporate a decent chain locker/electric winch
d) I would increase the V of the hull and give it rounder sections to minimise slamming although I suspect moving the engines forward would help substantially.

I think configured that way, the boat could take more power, such as some of the modern relatively light weight/high power diesels and that 30knts would be attainable.

Any boat builders out there listening?

Nick

 

[Guest]

Re: Diesel Mirage

Nope, not yet. And it may be a while yet as it looks as though my plans to be a kept man are evaporating as my missus is about to be made redundant and she's too old now to hang a red lamp on the door.

So, where my early retirement package was previously allowing my new business ventures to take their time coming to fruition, I have a bit more urgency in terms of turning them into money.

So boats, whilst not exactly the last thing on my mind, will have to wait for a bit.

Nick