Are we obsessed with power?

[onesea]

The term is largely irrelevant these days since most yachts are faster under power than sail in average conditions.

Have to agree I sail a 24 footer with a 6hp outboard. Its enough and once the wind is above a F2 its is quicker to sail so we sail. If we had the big engine we would probably motor allot more.

As it is if the winds not right we change our plans and sail some where else. Whilst being motored at* by yachts determined to get to there destination.

In fact when we get to the other end often most tenders have outboard of the same size or bigger than our main engine. I do wonder how many of those boats keep horses very well rested .

*Sorry passed , what is about sailing boats under motor that makes them think its fine for them to pass within feet in lighter airs? Normally under Autopilot only looking out occasionally or hiding behind spray dodgers leaving you thinking have they seen us?

 

[westernman]

When I first started in the yottie journo business, the rule of thumb for yacht designers had been for years 4hp per ton.

I have 85HP for 34 tons. Seems plenty to me for normal conditions.

However, it is a bit on the low side for heading directly into a F9 - the speed is down to about 3 knots through the water. Having done that once (and got back home on time), I don't want to repeat it - it is wet and uncomfortable.

Next time we will stay put another day and miss a day off work!

 

[ffiill]

Well my 43 hp Mercedes OM636 sucessfully got me through the Skye Bridge southbound against a rising tide al be it at one knot!.
Not out of choice and luckily I remembered how the ferries used to do it using the back currents.
Never forget the old 2 litre Rover side valve engine which just about delivered 40 hp happily took the Landrover series one up the sides of mountains.
The series 2 was not much better but fitted with an overdrive you could get 70mph out of it all be it at 20 mpg.
Never forgetting my OM636 which powered up the origional Unimog and Merc diesel cars well into the 1960s.
I do think there is a tendancy to overpower whether boats;cars or power equipment.
Particularly with a heavy displacement boat extra hp is not necessarily going to make it go faster.
Never forget once owning briefly an 18 ft Delquay Dory which came with a vertical straight six 120hp Mercury outboard-it went very fast and drained 12 gallon fuel tanks in a matter of less than 30 minutes!

 

[Blueboatman]

Having 24hp on approaching 9t loaded ( I think), the characteristics are more auxiliary assistance a la old petrol engines .
I can def sail a lot faster than I motor and coming out of harbour into any sort of headsea the trick is to get the main up pdq and 'tack'- just as we did with wee petrol engines in the past.
Otoh it is quiet, frugal, and reliable, unlike petrol engines wot taught me to sail. It does the business and stops well...guess I have a saily boat then.

 

[sighmoon]

It's a bit of a myth that a big engine helps you punch the tide. I've had 2hp on a 19footer, and 4hp on a 4 tonne 27 footer, and both could go displacement speed. Unless you are able to plane, displacement speed is all you can hope for.

Where a big engine helps is against a headwind, but normally sailing is more comfortable than motoring if there's a bit of a chop.

 

[Colvic Watson]

Our Colvic Watson has a design displacement of 13 tonnes in 34 feet, most actually displace nearer 15 tonnes. The original sales brochure offers engines from 30p to 150hp, as GL Watson knew a thing or two about design, the size had little to do with efficacy and was down to personal preference. As a diesel likes to be run at relatively high revs, in some ways the smaller the engine the better?

 

[Coaster]

As a diesel likes to be run at relatively high revs...

No longer true, for modern engines, or so Beta Marine told me before I bought one of its 38hp engines for our Westerly Seahawk. In calm conditions, with a Bruntons Autoprop this engine gives us 6 - 7 knots at very low RPM, keeping the majority of its output in hand until required to push through headwinds and rough water.

Like many people here we use our boat largely at weekends and need to keep to schedules.

 

[grumpy_o_g]

It's a bit of a myth that a big engine helps you punch the tide. I've had 2hp on a 19footer, and 4hp on a 4 tonne 27 footer, and both could go displacement speed. Unless you are able to plane, displacement speed is all you can hope for.

Where a big engine helps is against a headwind, but normally sailing is more comfortable than motoring if there's a bit of a chop.

Very true, but plenty of power swinging a decent-sized prop is handy when punching into those horrible South Coast short, steep seas too as you tend to to be stopped less and get moving again quicker when you do. Doesn't it make any more comfortable though

 

[BlueSkyNick]

I'm planning on buying a 40'+ yacht next year when I've sold my stink pot and the boat must have at least a 75hp engine. I'm not going to be in a hurry but after years of running around the solent like my hair's on fire at 30 knots trying to intimidate all you yotties means I need/want to get places within a reasonable time.
I also will still want to go on long journeys in a fairly short time due to work commitments so with a decent size engine I can!

I cant think of a 40' boat which will exceed its hull speed (approx 8kts) with a 75hp engine. Maybe a catamaran with 2 x 37's ?

 

[ffiill]

A good diesel should be a slow revving engine-problem was that as the demand came for more power for a given engine size so the higher revving indirect semi turbocharged diesels appeared.
The Nissan Terrano I used to own did 80 plus mph but at over 3000 rpm.
Compare this to my little Citroen C3 direct injection true diesel which does this at little more than 2000 rpm.
My Merc long stroke OM636 turns out about 7 knots at 1800 rpm in calm conditions.

 

[Ex-SolentBoy]

there are a few yachts that acheive their hull speed, apart from the Macgreggor yachts dont tend to plane (much) the SO 43 with the 75hp yanmar will do over 9, I have the 56hp and do 7.5. the SO 37 did 8.5 with 40 hp (turbo) option which is technically over its hull speed.

just out of interest I have been looking at the latest 43 ft offering from Jeanneau, its a similar size and weight to my now old SO43 but they dont offer any turbo charged engine options, as above they did two, 56 normally aspirated and 75 turbo, now they only offer 54 non turbo. - so perhaps power levels are comming down.

When we chose the engine/prop/gearbox configuration for the Rustler 44 we specifically made it so that the boat would achieve hull speed at maximum rated rpm, and in tests that has proven to be the case.

Of course, irrespective of these things, as long as you have enough power you should be able to reach hull speed. Whether you are willing to pay for the increase in fuel used is another matter entirely.