Tohatsu MFS9.8A3 UL 9.8HP 4STR UL (£2,141.41p) in westerly centaur with dead engine

chinita said:
Dylan keeps asking for the physics. Here is the physics as stated in Post#3:

This is the salient point, not debates about how much or little HP you need.
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That is at odds with what Mr Tohatsu at SIBS said about the engines designed for sailing boats. The physics is power=force*speed. Both a sail boat outboard and an inboard are geared/propped to achieve maximum power at 6-7 knots water speed.

As an aside, the new Dragonfly 32 can be supplied with either a sail boat outboard or a similarly powered inboard from new. The manufacturer states that performance under either engine is the same. I have not sailed either to know, but I am not surprised.
 
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AngusMcDoon said:
That is at odds with what Mr Tohatsu at SIBS said about the engines designed for sailing boats. The physics is power=force*speed. Both a sail boat outboard and an inboard are geared/propped to achieve maximum power at 6-7 knots water speed.

As an aside, the new Dragonfly 32 can be supplied with either a sail boat outboard or a similarly powered inboard from new. The manufacturer states that performance under either engine is the same. I have not sailed either to know, but I am not surprised.
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I think the engine will do as good a job as the original 10hp they fitted

you would want to put the outboard prop just where the current one is

same depth

Looking at this image

http://myweb.tiscali.co.uk/tonyandgi/Technical/Centaur26-brochure-p6.jpg

the outboard should be a fair way back in the capacious Centaur Cockpit

less weight but further back

so you would need more weight forward to geet her back on her lines

weight in the beam ends of any boat is not good

for me this is the worry

plus the slight loss of bouyancy from the well

D
 
Dylan while you are on here arguing the toss about something that is going to happen in 2019, you are not getting on with my DVD for Christmas.
Please desist and get on with it :)
 
Paddingtonbear said:
Dylan while you are on here arguing the toss about something that is going to happen in 2019, you are not getting on with my DVD for Christmas.
Please desist and get on with it :)
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Well,

at the current rate of progress with the journey I may need the full standing headroom before I finish

and maybe a Centaur with a great interior but a jiggered engine will come up in the right place at the right time

Cash flow is tough

Katie L is worth £8,000

if I can get a Centaur up and running for £4,500 that releases a lot of cash to spend on sailing

as for the DVDs

KTL4 and KTL 5 are being mastered - so the editing is done - now just waiting for the four year old editing computer to crunch HD films into DVDs

Eight hours of KTL amounts to a lot of digits

Son is doing the covers this week I hope

D




details as follows
 
dylanwinter said:
KTL4 and KTL 5 are being mastered - so the editing is done - now just waiting for the four year old editing computer to crunch HD films into DVDs

Eight hours of KTL amounts to a lot of digits

Son is doing the covers this week I hope
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My old Dad is 86 and always gets them for Christmas. There's nothing else he wants. We're all a bit worried (including him) that he might peg it before you get round to the crinkly bit of Scotland. Have you sees how many harbours there are before Inverness!
 
Austerby said:
I have a yacht with an outboard sitting in a cockpit well - an Achilles 24 (6hp 4-stroke boat displacement 2600lbs) - and it's coped perfectly well with difficult conditions, eg 30kts on the nose entering the Medway from Sea Reach against wind and tide. Was a bit wet but it punched through without struggling.
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and how much easier is it to shove an achillies 24 through a wave than a westerly centaur my friend? toothpick narrow with no freeboard compared to bluff bow centaur with loads of freeboard. one goes through the waves, the other parts them. both have their virtues, but htey are very different.

of course the tohatsu salesman is going to tell you his high thrust outboard is great. he wouldnt be a very good salesman if he didn't. the high thrust outboards are a step in the right direction but still dont have the prop area that you would have with diesel inboard.

If I had a DF920 I would not want an inboard. I'd definately go for an outboard. I used to sail an Iroquois cat which had a yamaha 9.9 4 stroke. right engine for the boat. If I had a J/80 I'd have an outboard.

the centaur is an (excellent) tubby little faimly cruiser that deserves a thumper of a volvo.

by the way, why does everyone on here only consider a dead inboard and a brand new one? I have fitted several decent used diesels to some of my yachts over the years and never looked back. After I overheated the seapanther in the 'tessa it was totalled. but I found another for £500 which worked a treat. If I bought a cheap centaur with a totalled engine thats how id go. you already got the shaft, the remotes the bearers, the fuel system the electrics. thats all the hard work done. shaft alignment is the only tricky bit and thats not too bad if you are methodical.

How about this Dylan. you have said this project will likely materialise in a few years time. Why dont you find a cheap second hand 25hp diesel, get a workshop manual, set the thing up in your garage and set about rebuilding it. Worst cast you'll still feel the same and you can sell the metal to the pikeys and probably get your money back. Best case you will enjoy the rebuild, realise that a naturally aspirated mechanical fuel injection diesel engine is probably the simplest engine around and as easy to work on as lego and at the end of it you will have confronted your demons and have a nicely restored and painted engine ready to drop into your cheap centaur as and when the right boat at the right price crops up?

as an aside, I have a spare engine that I have rebuilt for my boat on a pallete in the garage. Its just sat there gathering dust. but as my father who is a great believer in sods law says, a four foot square portion of my garage being wasted is a small price to pay for an inboard that will never break..... think about it
 
It should be realised that Dylan floats an idea every day, if nothing else it keeps his profile up in peoples' minds.

I doubt Dylan would ever be daft enough to go for the Centaur well idea, and probably ought to be hauled off to the funny farm if seen approaching a Westerly with a chainsaw - even if it was his Westerly ! :)

Today I crewed a re-engined Centaur around Hayling Island, saw a Mirage 28 with a well cut into it ( still feel queasy ) and had a mail from a chum with a Centaur with a duff engine; Dylan, do I win the Grand Slam ?!
 
contessaman said:
of course the tohatsu salesman is going to tell you his high thrust outboard is great
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He said no such thing, and neither did I say that he did. What he did say was that Tohatsu sail boat engines are designed to achieve full power at a boat speed of approximately 6.5 knots. I have no reason to disbelieve that statement as it seems an entirely sensible design decision by the manufacturer.

contessaman said:
the high thrust outboards are a step in the right direction but still dont have the prop area that you would have with diesel inboard.
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That statement is incorrect. My 9.9 Yamaha's propeller has a bigger blade area than my previous X99's Gori folding propeller driven by a 10hp Buhk. However, we are never going to agree on much on this subject, so I'm going to leave it there.
 
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contessaman said:
10 hp is nowhere near enough. to be able to punch the headsea with that bluff centaur bow and knuckle and the windage of that boat you need more like 25 or 30hp. and given a displacement hull its effectively the bollard pull you are looking at.
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I respectfully disagree, on two counts. First of all, not everyone wants a motorsailer; some of us are still quite happy with the idea of an auxiliary. Secondly, and as I wrote before, my 9hp Yanmar pushes close on 4 tons of 26' long fibreglass just fine. Of course the prop has to be suitable, and if a large and slower revving one is available that's what to go for.

Really the only downside of an outboard is the problem of a transom mounted one coming out of the water in biggish waves, but a well should solve that problem.

After all, what's the net result of putting an outboard in a well? A leg projecting below the boat with a propeller at the end, that's what, just like the saildrives fitted to every fin keeled yacht in the world, more or less).
 
dylanwinter said:
at the current rate of progress with the journey I may need the full standing headroom before I finish
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Hmm. The slug from the sarf to East Anglia, Katie L from East Anglia to the Forth, talk of a Centaur? By the time you get to the Solway I expect at least a million quid's worth of Gunfleet.
 
JumbleDuck said:
After all, what's the net result of putting an outboard in a well? A leg projecting below the boat with a propeller at the end, that's what, just like the saildrives fitted to every fin keeled yacht in the world, more or less).
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And, I suspect, a great deal more turbulence in the well than turbulence around an SD leg.
 
The Centaur was never a motor sailor, just gained that unfair reputation in the 1970's due to having what was then a big engine - 23hp wouldn't raise an eyebrow nowadays.

I do however agree with the idea of the engine being an auxilliary, this works fine on my boat which happens to have a slippery hull & good sailing performance, as long as one knows what one's doing.

An outboard engine in a boat designed for a well is one thing, but cutting into a boat designed for an inboard is quite another.

Wells and the outboards to go in them are best for boats under say 25' and IMO likely to be a disaster, not least structurally, if some bright spark makes his own for a Centaur or similar boat.

To operate a boat with a well properly the engine has to be lifted and stowed when one is sailing any distance, and a fairing plug fitted.

A well with engine in all the time creates a lot of drag, corrosion to the engine and a surprising amount of noise due to the turbulence; stowing the engine and fitting a fairing plug silences the noise and gives a major speed boost, also reduces vulnerability to lobster pots etc.

A well with outboard in is nothing like a Saildrive leg re drag etc ( well is worse ) and I have tried boats with either; though the well / outboard doesn't have the nasty big vulnerable gaiter with relative replacement & cost, hassle issues & prop vulnerability.

I do not believe a Centaur size / weight / shape boat could operate successfully with an outboard in a well.
 
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Hi Dylan

For purely personal reasons I'd love you to continue your adventures in a standard Centaur (ie with a glorious agricultural donk)

This is one of the combinations I regularly muse over so to see it action would be grand.

I think the time you'd spend with chainsaw and fibreglass could be better devoted to learning and loving diesel - time to get back on that hoss.

Main problem is you seem a couple of grand short of a good Centaur/engine

Have you thought of making a kickstarter project to fund the difference? - all you'd need is a promo video and promise of various DVD combinations for the rewards. It's only an afternoon on the computer away.
 
I have experimented with various well plugs on the Anderson 22 well ( which seems to compare better than most by allegorigal evidence ! ) , inc apertures for an outboard leg through the plug sealed by close brush bristles, split rubber flaps etc, also rubber flaps like small car floormats with the leading edge secured under the hull in front of the well, aft edge trailing free in the stream

None of them really worked, overheating through lack of cooling uptake - restricted water to the inlet - was one snag and one must realise this was in clear water, while the boat is probably going to be settling on soft mud at low tide which complicates things a lot more.

My conclusion - keep it simple as Oliver Lee intended !
 
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I'd expect to buy a secondhand diesel twin and install it for less than the cost of just buying the Tohatsu. So it'd be cheaper, less work, safer and more convenient to fit a new inboard. No brainer.
 
Seajet said:
The Centaur was never a motor sailor, just gained that unfair reputation in the 1970's due to having what was then a big engine - 23hp wouldn't raise an eyebrow nowadays.
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On the other hand, 10hp in a boat of that size wouldn't have raised an eyebrow in the 70s or 80s. It's only received wisdom now that every sailing boat must have a ruddy great engine in case the wind outside the marina isn't F3 on the beam.
 
dylanwinter said:
run me through the economics as you see them based on an old centaur with a jiggered volvo

D
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It cost me £1000 to buy a 5 year old Yanmar 1GM10, £20 for a new Vetus watertrap, £20 for a new length of exhaust hose, and £100 (or £80, I can't remember) for an engine panel. It took me a gentle weekend to install it in place of the obsolete BMW D7 which came with the boat and for which spares were unavailable.

I could have bought a similarly aged Nanni 14 twin for £1500 but it was a little wide for the Evolution's engine space which I didn't want to hack around.

Nanni Twin £1500
Watertrap £20
Exhaust hose £20
Panel £100

Total £1640 which is less than you can buy your proposed motor for, let alone install it.
 
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