One engine or Two?

[BrendanS]

What hope have we got then Brendan.....if it grows in pure diesel it doesn't matter how many tanks we have!

It means you can select bugs that will grow on just about any waste compound. Once you have selected those bugs, you can put them back into the same contaminated area, and let them decontaminate the place. A fairly lengthy process, but very effective. That's the short summary, as you can imagine, it's a bit more complex than that

As to two tanks, do many boats have multiple fuel tanks that are completely isolated?

 

[SnaxMuppet]

There is almost always a crossfeed valve that can allow the sharing of fuel to both engines. If I had a twin with separate tanks I would leave the cross feed closed to isolate each side and only open it if needed. That would also give me a better idea of consumption on each engine. Also, if a leak developed then it wouldn't drain both tanks and leave me with no fuel at all!

 

[Kawasaki]

One engine for Me.
Clean fuel, no air and Bobs Yer Uncle.

Best trip this Year so far.
Involved in a Tug delivery.
She was built in 1964
The Engine was taller and fatter than Me!
Cruising revs 450 rpm
Prop revs 150!
'Kachunka Kachunka Kachunka'!
Nice.

Twice I,ve been on a twin eng boats that have conked out.
One cos of dirty fuel.
First the Port eng stopped and not much later the starboard stopped.
Mucky fuel the prob.
Tother one had fould props due to rope and fishy net all wrapped round.
Yep fould props is luck of the draw.

Yep I like one eng.
Keeps things simple.
I like simple, it suits Me!

Lots of Commercial vessels run and run for Years on 1 lump.
No reason why pleasure craft shouldn't

Yep 1 eng, bowthruster is nice but not nessecary, once the quirks of propwalk have been mastered.

My old boat (1984) has one engine, thank Christ.
Cos I,m always mending it!
Bloody green pile of [word removed] word removed] etc etc!!!

Hactually I would like 2 engines like mine.
So I could strip one for Spares
Bloody green lump of [word removed] again!

 

[AndieMac]

I'm not feeling the (Volvo) love here Kwacka.....

 

[Kawasaki]

I'm not feeling the (Volvo) love here Kwacka.....

My 'love' transends the Globe it seems

 

[oceanfroggie]

Depends really on the type of usage you are planing and the area you intend to boat in. Long offshore passages, or short day boating trips, and everything in between.

One well looked after engine might be better than two badly maintained crocks. Old used but well maintained engines may be better than a newer engine that's been abused.

Twin offers handling, speed and a degree of safety, but from a mooring perspective a single with a bow thruster is just as easy to handle and costs half to maintain. I'd choose based on your planned type of cruising and usage rather than handling. In larger vessels a single may mean displacement cruising speeds (ie 7kt), wheras a twin probably offers planing speeds of 16-30kt.

 

[SnaxMuppet]

Kwacka, dodgy fuel would have stopped a single engine boat too so having a single wouldn't have helped would it.

I agree that commercial fishing vessels mainly have just one but almost all RNLI vessels have 2... even the inshore ribs... so what does that tell you?

 

[gordmac]

When I was looking for a boat I put having two engines down as a disadvantage basically for the reasons given here. Having ended up with twin engines I would have to say I am impressed with how much more control you have over the boat using the engines (and it is fun!) and that together with the need for two to fail to stop you getting home (no seastart here!) would now make twins very much a plus for me. Having said that you obviously need to weigh up everything.

 

[PCUK]

I agree that commercial fishing vessels mainly have just one but almost all RNLI vessels have 2... even the inshore ribs... so what does that tell you?[/QUOTE]

That we pay for them!!!!

 

[oceanfroggie]

I agree that commercial fishing vessels mainly have just one but almost all RNLI vessels have 2... even the inshore ribs... so what does that tell you?

Tells us nothing - Different requirement. Think of the few measly hours we leisure boaters depend on our twins each year, say a mere 50 to 150hrs per annum, compared to a fishing vessel that clocks up between 2000 and 3000 hrs per annum in ALL weather and atrocious sea conditions, and sucessfully depend on one well maintained single engine.

Fuel contamination may kill two engines just as quickly as one, as will fuel starvation. There is no right or wrong answer. We've had both, but see no safety difference between single and twin, nor mooring benefits. The difference tends to be speed and therefore wider cruiser passage windows.

Twin = Speed = Longer one day passage window
Single = Economy = Fuel Range = Extended Cruising Range

With a bow thruster a single is no less maneuverable than a twin.

 

[mainshiptom]

I would have two every time allthough I do think that 3 would be ideal where the two ouside ones would be large and middle one a get me home and slow cruising, would be Great..


Tom

 

[Chris_d]

Loads of arguments for and againest single or twin, I would go for single personely next time if i was buying a 30footer.
However I would definately not reccomend twin AD31's, horrible vibratory things at slow speed and noisy at high speed, and underpowered. Seem to be worse in a twin installation as they set up a terrible resonance.

 

[gjgm]

Cant recall the exact details, but I think based on the number of call outs, RNLI stats dont immediately suggest twins is any "safer".
Of course, running out of fuel seems a popular cause...
With twins, power steering is usually only on one engine, so you might have power, but only to go in circles!! And not all installation on twins are twin tank.
30ft with a b/thruster, I reckon one engine, some fuel filters, and good maintenance would be a pretty OK route to go.

 

[[2068]]

you might have power, but only to go in circles!!

It's perfectly possible to run on the engine that doesn't drive the power steering: you just need big muscles

At the 30ft, the single/twin debate really comes down to personal preference. imho, the main upside of twins is manoeuvrability. There is some benefit in the redundancy of powerplants if you're going offshore, but there is twice as much chance of something going wrong, twice the service costs, increased fuel consumption... etc. Having said all that, I like the warm fuzzy feeling of running with two engines

 

[Tidnock]

I think my old boat was a marginally underpowered, however, I once tried running on one engine, from memory there did not seem to be a massive difference, would this be correct or has my memory failed me?

 

[Kawasaki]

Kwacka, dodgy fuel would have stopped a single engine boat too so having a single wouldn't have helped would it.

Thats what I mean.
Doesn't matter how many engines!!

One engine to maintain.
Maintained properly.
IE, make sure the fuel is clean plus its container!
No air present etc.
It has to be easier to maintain one lump.

Plus having one, makes one more likely to keep on top of checks and servicing.
Shouldn't do but it does.
Physchologically peeps are more inclined to keep an eye on one lump.

Well thats the feedback I get!

 

[Corky]

One Engine or 2 - Interesting further info.

Thanks to everyone who's contributed to the debate.

The boats I viewed are Hardy Seawings 305. I tried out the 2002 single engine Mercruiser 250HP diesel engine and it seemed a bit slow. The dealer offered to check it out and the previous owner said he's never had more than 15Knots our of her. Does that sound right? The twin AD31's with 2x130 hp claim 22kts cruising 28kts max. According to the broker the single does have the right prop and has confirmed with their engineer she's in good order.

The older (twin) boat is like new but the attraction of a 2002 boat for a similar price is attractive.

 

[msimms]

We had a pair of AD31s in our first boat, 32 footer. The vibration/resonance at low speed was an annoyance particulary as we had a 50 minute slow run out to the Solent. I discovered that setting one engine about 200rpm higher than the other (may be a bit more or less) resolved the issue completely. Once on the plane there wasn't any problems at all running in synch.

Can't say I thought they were especially noisy either, maybe we had good sound proofing.

 

[silver_boy]

Thanks to everyone who's contributed to the debate.

The boats I viewed are Hardy Seawings 305. I tried out the 2002 single engine Mercruiser 250HP diesel engine and it seemed a bit slow. The dealer offered to check it out and the previous owner said he's never had more than 15Knots our of her. Does that sound right? The twin AD31's with 2x130 hp claim 22kts cruising 28kts max. According to the broker the single does have the right prop and has confirmed with their engineer she's in good order.

The older (twin) boat is like new but the attraction of a 2002 boat for a similar price is attractive.

15knots does sound a bit slow. Our S28 with the single 220hp version of that engine will do 26knots when clean.

Sounds like the Hardy is just struggling to get over the hump. Is it doing full revs at that speed (3600 or 3800) or round about 3000rpm instead? It may benefit from a pair of doelfins just to get the back end to lift that little bit more and get fully on to the plane.

Also our s28 can get stuck at that speed when it has dirty filters (remains of diesel bug) and can't quite get enough fuel through to give it the power to plane fully. Might be worth checking this out.

Cheers

 

[Corky]

250 horses - how fast?

Thanks for your thoughts on the subject. My 30ft Bayliner has a 260 petrol and will achieve 28 knots with a clean bottom which is why I thought to ask you guys. I would expect a 250 Mercruiser diesel to take this to a similar level. Maybe it's a long-standing fuel issue as you say.