2 engines or 1

[cuttlefish]

I am tilting more towards petrol outboards at the moment. I won't go into why because that would take uo another thread and tons of space and discussion. In any case, the meritds of diesels and petrol have been discussed many times, albeit there's always something new around the corner.

[Channel Ribs]

Originally Posted by rupert

I am tilting more towards petrol outboards at the moment. I won't go into why because that would take uo another thread and tons of space and discussion. In any case, the meritds of diesels and petrol have been discussed many times, albeit there's always something new around the corner.

So to sumarise, a cabin RIB of 7.5 or more powered by a single outboard, probably a 225HP?

[cuttlefish]

Nice name yours = makes me think of Malted Milk (Clapton).

To recap:
7.5/8.0 rib, canopy (not cabin), 250/300 HP outboard (preferably not electronic, but this is not a big issue). Aux. engine (which is what we are discussing here).
Comfort or suspension seats. Probably not more than 4 in the cabin area.
Usual electronic aids: depth sound, VHF, GPS, radar would be useful (have been out in fog around Guernsey before...), safety features, etc.

[Channel Ribs]

Originally Posted by rupert

Nice name yours = makes me think of Malted Milk (Clapton).

It seems some beggar on eBay agrees, they have signed up using "Malthouse Motors and Marine". Why I outa.

Sorry, back on thread.... I would rate a RADAR as more important than an auxiliary motor, as you know 30kn fog is scary stuff! (And far more common than engine failure.)

[cuttlefish]

I agree totally. Radar is damned useful in those conditions.

Re. the second engine, it's not such a problem from Gsy to Sark, but rather the Dielette - Gsy/Sark route which concerns me if I have engine failure.

[9D280]

Cyp, apologies for jumping on yours rather than any other posts, but it was a useful list to make a comparison with.

Originally Posted by Cypman

Extra weight.

Tohatsu 2-Strokes. 60Hp - 115 Kg. 30Hp - 52Kg. 2x 52Kg = 104Kg, and that's before you add 20 odd Kg of aux......... That will alternate between bifg single & twins al lthe way up the horsepower range of any manufacturer.

Originally Posted by Cypman

loss of HP of around 25%,

errrr (Hp/2)*2 = Hp.

I assume you mean the effective horsepoewer drop, which is essentially down to HP lost by pushing more leg through the water, but I covered that already. (see my post above)

Originally Posted by Cypman

double servicing costs,

Can't argue with that!

Originally Posted by Cypman

extra drag,

See previous post - but it's all down to your speed & the frontal area of your engine leg. If you cruise at 20 odd knots it'll make a lot less divfference to your fuel consumption than if you cruise at 40. My Merc 60 has the same sized leg & prop as my Suz 25..... Two of them would be a lot les drag than 2 modern 60Hps that will share their leg with most engines up to 90Hp & are therfore Overkill for the smaller HPs

Originally Posted by Cypman

initial cost

Googled "Yamaha price list" - I'll go Big Hp 4-stroke this time to show it's not just a "small engine" phenomenon:
F100 - £8699; F200 £15,799; F9.9 (aux) £2699

2xF100 = £17398
F200 + F9.9 = £18,948



Mollers points out his performance on 1 engine is naff. Of course it is - you're only running on one! We're talking get out of jail here - not the optimal perofrmance between two boats one with half the hosepower. 20 knots on the "Aux"? I'm lucky if I can pull 2 Knots on mine! On a similar theme I have used a 5.4 Searider / Twin 30s that ran happily if sluggish 5 up with one engine dead.


What I'm trying to point out is that the usual "knee jerk" reactions to twin engines are not always true.

Rupert, if you have time, take your time, do the research, base your decision on data. You'd be surprised what you might find.........

[cuttlefish]

(d wrote: "Rupert, if you have time, take your time, do the research, base your decision on data. You'd be surprised what you might find........."

I'm doing my best. I have the time, but I am not sure that I have the brains!"

[willk]

Originally Posted by Mollers

My Redbay will plane at about 20kts on one motor at WOT (with the dead stick in the water). It IS overpropped for single engine use (19 pitch) and has to be coaxed out of the water and she isn't making her normal revs either. I wouldn't fancy trying to maintain plane in short lumpy water.



Surely that blows away one of the main planks of the twin argument?

Originally Posted by 9D280

Mollers points out his performance on 1 engine is naff. Of course it is - you're only running on one!

I think his problem might be that Redbay of his...

[Mollers]

Originally Posted by 9D280

Mollers points out his performance on 1 engine is naff. Of course it is - you're only running on one! We're talking get out of jail here - not the optimal perofrmance between two boats one with half the hosepower. 20 knots on the "Aux"? I'm lucky if I can pull 2 Knots on mine!

Of Course!! Try buying a decent auxillary not a w**ked out Moulinex.

[9D280]

Originally Posted by Mollers

Of Course!! Try buying a decent auxillary not a w**ked out Moulinex.

Can't argue with that!

Still doesn't alter the fact that with my theoretical max displacement hull speed even if I bought a nice shiny new fuel injected 6 horse 4 - stroke I'd still be able to walk faster.........

Difference is your one engine can get you on the plane.

[Mollers]

Originally Posted by 9D280

Can't argue with that!

Still doesn't alter the fact that with my theoretical max displacement hull speed even if I bought a nice shiny new fuel injected 6 horse 4 - stroke I'd still be able to walk faster.........

Difference is your one engine can get you on the plane.

Yeah, the Kenwood needs to be in the 10-15hp region.

[9D280]

Which I don't have space or transom weight capacity for.......

Maybe I should fit it with doel fins?

[cuttlefish]

but still on the engine theme.
What difference in price am I looking t with diesel and petrol engines?
The question is general and not limited to any particular model or boatbuilder, but as an example, most of you reading this thread know that I have been looking at Redbays, they offer sterndrive diesel engines and Suzuki outboards. Presuming the equivalent power unit, what price difference is there, and can this be justified in terms of maintenance, cusmption, etc?

[Poly]

Originally Posted by rupert

but still on the engine theme.
What difference in price am I looking t with diesel and petrol engines?
The question is general and not limited to any particular model or boatbuilder, but as an example, most of you reading this thread know that I have been looking at Redbays, they offer sterndrive diesel engines and Suzuki outboards. Presuming the equivalent power unit, what price difference is there, and can this be justified in terms of maintenance, cusmption, etc?

I've never heard anyone claim that inboard diesels with sterndrive legs were cheaper to service than outboards. Perhaps somepeople used to feel outboards were not as reliable, and diesels very simple/robust? But I'm not sure that applies - modern outboards are very good and modern marine diesels are increasingly sophisticated with electricarry to make them work.

When considering economy you'll need to bear in mind that dockside fuel prices in the CI (and France) may be quite different from the UK. Even when red diesel was avaialble essentially duty free to leisure boats in the UK there weren't many people who believed that the extra cost of a diesel would payback in fuel costs for a typical pleasure user. One of the drivers for diesel - is availability of fuel on the water; I'm not sure how much that will apply in your planned area of use. e.g. if you were planning to cruise parts of ireland and the west of scotland that may tip your decision towards diesel. Alternatively if you have petrol available at your home port it might just encourage you to spec a bigger tank.

[cuttlefish]

However, what would be the diff. in price for the same boat with a sterndrive diesel and an outboard?

[Poly]

Originally Posted by rupert

However, what would be the diff. in price for the same boat with a sterndrive diesel and an outboard?

By way of example, from the 2007 Redbay price list a given boat is quoted as:

165 HP Yam Diesel -- £44.2k
240 HP Yam Diesel -- £49.2k

200 HP Suz 4/ -- £37.1k
175 HP Etec -- £36.9k
225 HP Etec -- £ 38.8k

Hope that helps - prices are obviously out of date.

[cuttlefish]

we could be looking to pay up £10k more for the diesel. That is fair whack to be justifed by fuel prices.

[Andre]

Interesting thread and more interesting will be the conclusion.

don't forget that the price difference is not just the difference between both engines but there is much more work involved when fitting a stern drive then an outboard.

[Poly]

Originally Posted by rupert

we could be looking to pay up £10k more for the diesel. That is fair whack to be justifed by fuel prices.

Yes - and what I didn't very elegantly manage to say is you probably won't justify it on that basis (alone) - but if getting 200 L of petrol to the boat for a weekend of fun is going to be a much bigger PITA than filling with diesel in the harbour then you might feel it justifies it.

[cuttlefish]

Don't forget that the price difference is not just the difference between both engines but there is much more work involved when fitting a stern drive then an outboard.
__________________

Exactly! and that should make the difference in prices even more pronounced.