wasnotwas
Well-Known Member
Hi was just wondering could you guys give me your views on the pros and cons of single engine opposed to twin thanks for your help...
1 screw or 2?
- Thread starter wasnotwas
- Start date
neale
Well-Known Member
Single
Better fuel economy
Easier access to engine for Servicing and maintenance
Half price servicing and maintenance
Higher speed for same HP or same speed for lower HP
Twin
Spare engine in case one breaks (but not always if problem is fuel related)
Easier manoeuvring
Are you thinking Shafts or Drives?
Better fuel economy
Easier access to engine for Servicing and maintenance
Half price servicing and maintenance
Higher speed for same HP or same speed for lower HP
Twin
Spare engine in case one breaks (but not always if problem is fuel related)
Easier manoeuvring
Are you thinking Shafts or Drives?
wasnotwas
Well-Known Member
sorry forgot to mention they would be single or twin shaft drives i was asking about
Firefly625
Well-Known Member
shafts, the only way to go.... as far as single or twin.... nothing to add to Neale above
mlthomas
Well-Known Member
Depends what you want to do, size of the boat and general sea state where you are going to be based.
omega2
Well-Known Member
one or two??
Always wanted two, following a miserable time with a single on a leg, now got two on shafts, but with the cost of fuel these days a reckon single is probably the way to go, but it must be shafts, even though the legs are a bit more frugal.
Always wanted two, following a miserable time with a single on a leg, now got two on shafts, but with the cost of fuel these days a reckon single is probably the way to go, but it must be shafts, even though the legs are a bit more frugal.
powerskipper
Well-Known Member
my 2 pennys worth
A single shaft is not an easy boat to learn on, a twin shaft is much much easer and you have normally at least one working if something goes wrong so can often at least get yourself some where, if you go for the single , put a wing engine or back up out board on her for safety.
A single shaft is not an easy boat to learn on, a twin shaft is much much easer and you have normally at least one working if something goes wrong so can often at least get yourself some where, if you go for the single , put a wing engine or back up out board on her for safety.
Jim@sea
Well-Known Member
When I started boating in the early 60's I was told " Twin engines,halve your problems"
I would never dream of going offshore without either twin engines or a single inboard with an outboard which would give 6 knots.
Once one of my propellers got caught with an unmarked lobster pot line and stopped, fortunately I had my other one. There is no AA or RAC out there. Would you buy a plane without buying a parachute, because the parachute gives you the second method of landing.
I would never dream of going offshore without either twin engines or a single inboard with an outboard which would give 6 knots.
Once one of my propellers got caught with an unmarked lobster pot line and stopped, fortunately I had my other one. There is no AA or RAC out there. Would you buy a plane without buying a parachute, because the parachute gives you the second method of landing.
pheran
Well-Known Member
Hmmm.....I wonder where they keep the parachutes on commercial aircraft. I always get the location of the life-jacket pointed out to me but never the parachute!!
neale
Well-Known Member
You could equally say "Two engines, twice as much to go wrong"
I am not saying either is best, just that they both have advantages and disadvantages. I have been cross channel many times in single and twin engine boats.
oceanfroggie
Well-Known Member
Depends on what you want to do.
Singles good for economic displacement cruising, for inland shallows as shaft and prop protected by keel and skeg. Single with bowthruster as easy to handle as a twin
Twin good for planing, depending on sea state higher speeds can be more comforteable in swell (ie less rolling). Slight safety advantage, but one well maintained engine is better than two dodgey ones.
As to fuel contamination most twins have completely separate fuel tanks and system for each engine to cross contamination should not occur (requirement for BSS btw). Rope cutters for shafts recommended. A bow thruster is a great help on singles over 35ft.
neale
Well-Known Member
While I agree entirely with that comment, you mustn't forget that fuel tanks are nearly always filled from the same source so although cross contamination is unlikely, but not always impossible, it is possible that contamination will be introduced to both tanks at the same time anyway.
Defo agree about bow thruster comments. On a twin it is a nice addition, on a single it makes handling soooooo much easier it is almost a requirement. (dons tin hat and waits for HLB
)
Philiz
Well-Known Member
Defo agree about bow thruster comments. On a twin it is a nice addition, on a single it makes handling soooooo much easier it is almost a requirement. (dons tin hat and waits for HLB
Nah, you're safe, I reckon HLB will agree with that. FWIW I agree totally.
David_J
Well-Known Member
Cannot actually disagree but we learnt on a shaft single (with bow thruster) and it was ok, in fact kept that boat for five years without problem. No breakdowns no ropes on the prop. The engine was regularly well serviced though. We particularly wanted a single shaft for the economy and simplicity. Most of the fishing boats out there are single engine, so are a lot of larger commercial vessels. There is a lot of irrational fear around single engines in the pleasure boat world. I think the main problem comes from minimal use and less than the best maintenance!!!
We now have a twin shaft. Last year the VP D4 engines had less than 100 hours on and one of them stopped at sea three times. Then a few months later same engine got ropes and netting round the prop which overwhelmed the rope cutters. We got to be pretty good at mooring on one engine so the time with the single shaft was good experience and a two engine set up rather useful.
So its fairly easy to make a case either way really. Been there and dun both.
I like having two engines to play with and it is comforting but it is double the maintenance costs. I think I could be happy with a single shaft again but on the bigger boats a wing engine or outboard is often not practical. Beneteau have been selling the 34 trawler like crazy over the last year and thats a single shaft. In fact there are three of them on the pontoon in Brighton.
ian38_39
Well-Known Member
David _J, What would have happened if you had changed your boat to one with a single D4 and the single had been the one that let you down 3 times and then got ropes round it. on all occasions you would have been calling out for help.
We all know that one engine is never identical to the next, even in cars, so the comfort at having two goes at getting one right is a big pull for 2 lumps.
We all know that one engine is never identical to the next, even in cars, so the comfort at having two goes at getting one right is a big pull for 2 lumps.
neale
Well-Known Member
I doubt anyone will say that having a second engine is a bad idea for reliability and emergency backup, it's a no brainer really. When I wrote my list of pros at the beginning I though others would chip in with more that I didn't think of immediately. As it happens we are left with just 2 Pros for a twin engine. One of them in manoeuvrability, which can easily be matched with a bow thruster, so that just leaves this one important feature.
It is then up to individuals as to whether the benefits of a single, and I forgot to add the large financial saving when buying the boat, is worth the increased risk of being stranded if things go wrong.
To show my hand, I own a single (with a bowthruster) but I clock up more hours each year on a twin.
Because my single engined boat is small, 25ft, I get around the problem with an aux outboard, so I actually manage to hopefully have all the pros for both types. Admittedly if we are looking at bigger boats where a 10hp outboard is going to be as useful as a chocolate teapot, the decision may be a little harder to make and ultimately may come down to money, both in purchasing costs and the significantly reduced running costs.
You pays yer money...........
ian38_39
Well-Known Member
I suppose the question to ask is, of the twin owners, How many here have been forced to come home on one engine at some point?
I haven't so far so I guess you could say that is a reason to buy a single.
I haven't so far so I guess you could say that is a reason to buy a single.
neale
Well-Known Member
Or just as importantly how many times have you had to accept a tow, to both single and twin owners.
In my professional capacity I have had to tow a few twin engineed boats into harbour with things such as a double wrap on the props, not as uncommon as you might think, double fuel contamination, steering failure or in more than one case, the single engine that is still running does not control the power steering and the owner has simply found driving it almost impossible.
As a twin with only 1 engine will become a displacement boat, it is also susceptible to the waves and I have seen one occasion where the skipper became incapacitated by seasickness after loosing 1 engine and required outside assistance for that reason.
It is fair to say though that I have seen many more cases where the twin was able to limp into port on a single engine, I have done it myself at least once, so it is definitely beneficial to have 2, but not necessarily a clear cut decision where money is concerned.
A well maintained single is better than a pair of neglected engines, and if access, money and the thought of loosing your only means of propulsion make you take better care of a single, then so much the better.
BGW
Well-Known Member
I have had to rely on one engine on my old boat (diesel bug in one of the tanks.) but I agree, with correct maintenance the reliability issue is a moot point.
I am not sure it can be said that a bowthruster will match a second engine for maneuverability - the action is very different (and I don't necessarily mean it's worse).
Unless an overpowered (by normal calculations) thruster is fitted, it can struggle in strong winds with a high windage boat - and the batteries (and motor) will only last so long - the second engine will run as long as the fuel lasts.
For another plus, I can run at the same speed as a single engine craft (of the same design) with much lower revs, so it is more quiet and comfortable on longer passages.
I do my own servicing, so the extra cost is negligible for the security of the second engine. The design of my boat would not lend itself to fitting an auxiliary engine.
pheran
Well-Known Member
The trick here is to fit a stern-thruster as well. Our boat, 13 metres and 13 tonnes, has both and we can be moored up and having a drink while the twin-engined skipper is still fiddling with his throttles!
We have had several twin-engined boats in the past but 'thruster power' definitely has quite a considerable edge. And its not a question of fitting 'overpowered' thrusters. Its a question of matching them to the vessel. I suspect too many owners have tried to economise by fitting one that are too small.The secret with a single-engined boat is the right sort of motor. The last thing you want is the loaded with electronic controls, over-developed, over-stressed lumps offered by so many manufactures today. Higher capacity, slower revving, are a much better bet in the reliability and longevity stakes albeit at the cost a little (but not a lot) extra space and weight. Iveco are a good example of what I mean. Tend to run quieter too.