Petrol vs Diesel

[Suenoespanol]

Petrol vs diesel I’m looking at a boat 27ft sports cruiser with a 377 Mag Mercruiser 2014 low hrs and very nice at good price point. To be used in the Med pottering around occasional longer trips. Just wondering how good and efficient they are compared to an equivalent diesel. Iv always had outboards and boats up to 23ft. People talk about high maintenance for inboards ie risers,bellows gimble bearings etc. Opinions,advise all welcome. Many thanks in advance. Good idea or should I stick to outboards?

 

[Tranona]

Welcome

You will probably get more response if you post this on the motorboat forum

 

[William_H]

Modern 4 stroke outboards with fuel injection are really good on fuel consumption etc. There are no advantages and more disadvantages using an inboard petrol engine. However diesel has it's advantages of fuel fire safety and economy of fuel consumption. (resulting in vastly better resale value)
All this as I see it as a non mobo owner. Decision is up to OP based on cost of boat and general feeling. No we can't help him make a decision . ol'will

 

[Suenoespanol]

Petrol vs diesel I’m looking at a boat 27ft sports cruiser with a 377 Mag Mercruiser 2014 low hrs and very nice at good price point. To be used in the Med pottering around occasional longer trips. Just wondering how good and efficient they are compared to an equivalent diesel. Iv always had outboards and boats up to 23ft. People talk about high maintenance for inboards ie risers,bellows gimble bearings etc. Opinions,advise all welcome. Many thanks in advance. Good idea or should I stick to outboards?

 

[oldgit]

If we for the moment disregard the mechanical advantages/disadvantages between inboard and outboard propulsion systems ................
Only intend to to whizz round the Cala and back ? then petrol might well do the job , if you actually want to go anywhere in your boat , its diesel all the way.

In UK petrol boats larger than small speedboats are always considerably cheaper to buy, than their diesel counterparts and usually in much better condition, mainly due to lack of hours run, its all down to cost of petrol compared to marine diesel.
In the UK, a jealously guarded fiddle known as "Red Deisel" has long distorted the boating market, this is not available elsewhere .

 

[PlanB]

Apart from anything else, check out the availability of petrol in your local marinas, unless you intend to fill using cans.
There is a current thread elsewhere on here on petrol vs diesel.

 

[Canopy Locked]

For me personally, the safety implications of an inboard petrol engine would be enough for me to completely dismiss an inboard petrol boat. For petrol I'd always go outboard - but for a boat 27+ ft it'd be diesel all the way due to the fuel consumption.

 

[Suenoespanol]

Apart from anything else, check out the availability of petrol in your local marinas, unless you intend to fill using cans.
There is a current thread elsewhere on here on petrol vs diesel.

Other than lpg all available. Good point thanks.

 

[Grubble]

Apart from anything else, check out the availability of petrol in your local marinas, unless you intend to fill using cans.
There is a current thread elsewhere on here on petrol vs diesel.

Spanish marinas have petrol and lots of petrol boats. Unlike the UK, Spain never had red diesel, so the cost advantage of diesel over petrol is minimal when you take into account the higher initial purchase cost of a diesel engine versus petrol, unless you are going to be doing serious amounts of cruising.

If the OP just wants a day boat to zoom around in, petrol will be fine. If they want to go cruising then diesel will be the better option.

 

[PCUK]

Welcome

You will probably get more response if you post this on the motorboat forum

?

 

[Tranona]

?

It was originally on PBO, but has now been moved. OK?

 

[Moderator]

PBO and Mobo threads merged, here.

 

[Refueler]

I went through this decision state ... and in the end took the Inboard Petrol ... a 170HP Volvo Penta 6cyl job in a 24ft Primor. I basically looked at price differential and thought about how long to recover the money ..

I brought - home cleaned up and launched .... dreading the anticipated fuel bill. Figures of 25lt / hr were running round my head from what others had said ....
Well I was actually surprised at reality. Yes if I wanted to zoom around at 20kts plus .. I could burn over 20lt / hr. But settling at cruise speeds of 12 - 15kts .... I was down to 10 - 14lt / hr ..... in fact depending on how I throttled / trimmed etc. - I can expect the lower figure even at the 14 - 15kt mark.

Of course a diesel boat would be more economic to run - but there is also the sound factor ... the petrol engine I have - has sound insulation but its not that thick - engine sound is a steady purr ... but diesel boats I've looked at - needs more sound proofing to have cockpit conversation at normal level

 

[Suenoespanol]

I went through this decision state ... and in the end took the Inboard Petrol ... a 170HP Volvo Penta 6cyl job in a 24ft Primor. I basically looked at price differential and thought about how long to recover the money ..

I brought - home cleaned up and launched .... dreading the anticipated fuel bill. Figures of 25lt / hr were running round my head from what others had said ....
Well I was actually surprised at reality. Yes if I wanted to zoom around at 20kts plus .. I could burn over 20lt / hr. But settling at cruise speeds of 12 - 15kts .... I was down to 10 - 14lt / hr ..... in fact depending on how I throttled / trimmed etc. - I can expect the lower figure even at the 14 - 15kt mark.

Of course a diesel boat would be more economic to run - but there is also the sound factor ... the petrol engine I have - has sound insulation but its not that thick - engine sound is a steady purr ... but diesel boats I've looked at - needs more sound proofing to have cockpit conversation at normal level

Thank you for your info based on personal experience. The one I’m considering is a V8 Mag 377, 320 hp 27ft. I guess it’s all about usage and how heavy you go on the throttle weather, trim etc. hopefully a calm med (not always )will help.

 

[Momac]

....... there is also the sound factor ... the petrol engine I have - has sound insulation but its not that thick - engine sound is a steady purr ... but diesel boats I've looked at - needs more sound proofing to have cockpit conversation at normal level

Noise is a consideration. I know someone who sold an otherwise good boat due to the noise levels. It was great on the river but unbearable at fast speeds.
I have diesels but thankfully the flybridge helm is remote enough from them to make the noise acceptable.

If petrol was much cheaper than diesel it would be more popular than diesel.
In some areas the availability of fuel (or the lack of it) at the waterside is also a consideration in favour of diesel.

 

[kawasake]

Get a diesel with shafts
Or
A petrol with outboards
Outdrives driven by diesel or petrol?
No
Not in my experience of owning all types
Over the last 40 or something years
25 of which have been either as an Instructor or a commercial skipper delivering motor boats , mending motorboats or just faffing about with motorboats!

 

[ontheplane]

I had a 26ft Rinker with a 5.7V8 petrol and the fuel cost was unbearable (for me).

At a moderate cruise (say 15-20kts) it would burn around 20 gal an hour (say 90 litrs) so a trip of 40 miles say would burn about 180 litres of fuel - which at todays marina prices in UK would be about £380 it meant I never used it for what it was for, and just pottered out to the bay swam off it and came back.

If you want a speedboat then fine - if you want to cruise anywhere it's got to be diesel - I hear that the modern outboards are good - and I guess they are, but even they will still burn a lot of fuel - I see boats with twin 300 hp motors and dread to think what they must burn at half throttle.....

I think the cut-off for me is about 20-22 ft - under that, Outboards, or a modern MPi inboard petrol is probably ok

Over that, the sheer weight of the boat and power needed to move it makes it diesel only....

Just imho obviously.

 

[julians]

I used to have a 22 foot sea ray with a 5.0 mpi mercruiser inboard engine, it would burn about 50 litres per hour at cruising speed of about 25 knots.

Then I swapped to a 25 foot windy with a volvo penta d4 diesel, that burned about 30 litres per hour, so lot less fuel was used, but the boat itself cost a lot more to buy in the first place, and volvo penta parts prices are eye watering compared to mercruiser. I think overall the diesel windy cost more to run per hour than the sea ray with petrol inboard

Now I have an axopar 28 with 300hp mercury petrol outboard, and I'm back at 50 litres per hour at cruise speed, but much lower per hour overall running cost due to much lower servicing costs of the outboard.

I'm in the med, I'd say petrol would be fine for what you want, but I'd try and go for outboard over in boards. I think these days most boats in my marina under 30 feet use petrol, and even in the 30 foot to 40 foot sector there's a fair proportion using petrol.

Other factors that differentiate between petrol and diesel are

- noise, petrol is quieter
- smoothness, petrol is smoother
- fire risk, higher risk of fire with petrol, but you need to balance this against the sheer number of petrol boats in use in the world without problem.
- fuel availability, varies by area, apparently a bit of an issue getting petrol in UK, not an issue at all in the med hot spots

 

[Refueler]

Lets look at other aspects :

Inboard shaft drive ... many are diesel ... and then you have to lift out for any inspection of prop etc. Manoeuvrability is good but all depends on placement of rudder and size. Engines are usually car engines marinised.

Inboard with z drive - as I see it - about 60-40 split petrol vs diesel. Prop can be casually inspected by raising leg .. manoeuvrability is generally better than shaft drive as the thrust is directed rather than deflected by rudder. Maintenance of bellows etc. But servicing is split and legs are lighter than Outboard to remove ... engines are usually car engines marinised.

Outboard - near all petrol with very few today as diesel. Manoeuvrability as with z drive - better than shaft. Heavy lump to lift / service.

Fuel Consumption .... even with todays 4str Ourboards - they tend to be thirsty beasts .. talking to owners - I have been told the inboards are better on fuel economy.
Outboards - can be noisy ...
Diesels are noisy with a harsh sound.

For manoeuvrability and servicing (leaving aside costs) - I went for Z drive.
So far I am happy .. just had leg serviced and 'rubbers' replaced - 1 day job by yard ... 250 euros + parts .. total 310 euros.

 

[oldgit]

In conclusion ?
For most of us , that careful thoughtful "plan" regards boat buying has all the lasting power of a chocolate teapot.
The first boat that catches our eye, however impractical....................and all that "good" advice goes out the porthole.
Have always admired those with the cash to have a spreadsheet logical approach to boat purchase and the ability to buy the boat they want.
For most, its what you can beg borrow or steal and then end always somehow spending twice that amount.
Then follows a few decades of poverty stricken chaos, buying slightly less and less unsuitable boats as you go along until you finally learn you can never afford the boat of your dreams and actually already probably have the boat that best fulfills your needs.

Enjoyment and pain of this little adventure is priceless. ?

You know you have reached the end of the journey, when being forced to moor next to some enourmous shiney brand new rocket ship gin palace , your first thought is actually sympathy , knowing all the things that can and will go wrong with it.