Re-engining my Kingfisher 30

[DGuthrie]

My Kingfisher 30 was equipped with a Watermota SeaWolf 33 hp petrol engine, now removed. I want to replace the engine with a new diesel. Herein lies the dilemma: what size (i.e. hp) engine should I have installed?
Engineer Eric, a Nanni agent, says I should replace with a Nanni (natch) 28hp. Engineer Alan, a Vetus agent, says all I need is a 16hp unit. Alan was recommended to me by his former partner in the business, Euan, who took detailed info from me about clearances for the prop and said a 12 - 14 hp motor was right. The surveyor (on purchase in March this year) says I need 10hp plus about a 25% margin.
The boat is 30ft (25ft LWL) displacement 3912kg and the maximum prop diameter she can take is 13 in.
Arguments are as follows:
Engineer Eric says Nanni won't warranty a 16hp unit on this boat in case it burns out. 28hp - or more - is needed given the displacement of the vessel plus a couple of tons for crew and fuel (2 x 30 gallon tanks in the keels) and kit and the need to proceed against strong adverse wind and tide.
Engineer Alan says that there's little point in putting big hp through a 13 in. shaft-driven prop; that, whatever the conditions, the 16hp engine can run all day on full revs, no sweat.
My own feeling is that I'd like to KNOW that whatever I put in the engine will punch through whatever the weather throws at me for however many hours it takes to get to safety.
Both engineers have an interest in selling me an engine.
Some say you need 4bhp for every ton of weight (which would make 28hp about right).
My bro -in- law has a Macwester 27 with a 10hp Sabb diesel which gets them through whatever's going on.
My chandler has a Hunter Channel 31 with a 10hp motor which seems to do the job.
Engineer Eric is giving the old dire warnings about safety and all that.
Muggins here in the middle knows not which way to turn. Obviously I want the best for the boat, but am constrained by cash but will install the right motor - but what IS the right motor? We have ambitious cruising plans - round Britain, over to Norway, Holland, France - and therefore want to know that what we fit is up to it - given that we do intend to SAIL the boat!
Someone out there, please throw some arguments our way?
Any guidance, formulae or personal observations would be welcome

 

[sailorman]

28hp Beta
this from a satisfied Nanni owner who could have saved £1100.00 with a Beta

 

[cliff]

34' Sadler with a Bukh DV24 - no problems - sufficient power for the job, has run at 3/4 ~ full throttle for over a week non stop without any problem (rare in uk waters - no wind for over a week)

If you want a little extra power Bukh do a turbo version of the DV24
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"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[boatmike]

Confusing isn't it? In terms of make, you have a wide choice, although I believe the Beta are very good value. Shop around. Look at the space you have and the weight of the different makes, don't buy an overly heavy one and check the dimensions against your engine bearers and space availability. They vary considerably.
As far as power is concerned you only really need 15HP to act as an auxillary but anything from about 20-25 HP will give you slightly more top speed and more importantly power to stem foul tides and make way against a headwind. I am surprised you previously only had a 13in prop on a 33 HP engine but it depends on RPM which will be determined by the gearbox ratio. If you are constrained to such a small prop consult the engine manufacturer with regard to the appropriate gearbox ratio. There is often a choice of gearboxes. For a vessel of this size and displacement I would look for about 20-22HP personally, but if a little bit more is available without a big weight penalty no problem. Anything over 25 would seem to be wasted though.
The advice regarding a smaller engine "burning out" is rubbish. Diesels like to work hard and a small one at full chat is better than a big one at half speed all day. Avoid this dealer he is talking rubbish in my opinion.

 

[cliff]

[ QUOTE ]
check the dimensions against your engine bearers and space availability. They vary considerably.

[/ QUOTE ]Good point! The costs of altering the bearers could very easily outweigh the savings made by buying a "cheap" engine if you need major alterations to the bearers. Also consider the prop size and fit the largest dia you can leaving sufficient tip clearance between the blade tip and the hull (10% of prop ø?).

Measure carefully the height of the prop shaft in relation to the bearers etc and compare with the gearbox output shaft height.
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"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[andy_wilson]

I think you will struggle to run with 2 tonnes of crew and stores. Your fuel will be 250kg, massive water tankage the same, 4 crew at around 80 kg each leaves you 200kg for food and safety kit. With a liferaft, dinghy and motor you might just get over 1 tonne.

Eric seems to be talking a load of crap. 16hp will run all day at 16 hp if the prop. is the right size to absorb the power, if you want it to and if you can stand the noise. It will surely get you beyond the hull speed, giving some power in hand in the event of a dirty bottom, strong headwind, or to maintain speed if the chop keeps knoking you back.

Where 16hp might cause a slight problem is if it is coupled with a large alternator feeding flat battery banks, particularly through an advanced regulator. These might conspire to prevent engine revs. rising whilst in gear. The solution however is a MUCH BIGGER engine as at the revs where charging load rises to maximum (say 1500rpm), the engine will only be developing 3 or 4 hp.

I would say up to 20 hp would provide a bit of cover in case you have a dirty bottom AND a headwind and chop.

Most impirtant I would say is get the engine that fits with the least work. Major engine bed, shaft and ancilliary work can double the cost of the replacement.

 

[DGuthrie]

Gentlemen, I am most grateful for your observations - and so speedily offered. The consensus seems to be trending to the 16 - 20+ bhp range. More views would be welcome. At this rate, I'll have a representative sample worthy of the Today programme! Thanks again, Cliff, Mike, Andy and Sailorman. Pints all round if you're in Newcastle ever!

 

[maxi]

My boat is similiar in size to yours but somewhat heavier. I recently installed a 28hp Kubota (Nanni-Beta), and have found the ngine size to be just about right. I am however driving a 15" propeller.

I really think that whilst a 16hp will get you along, you will have no punch in reserve and a pretty mediocre speed band.

 

[stevebirch2002]

Have a look at the Beta BD722 (3 Cyl 20HP) or their new 25HP 3 Cyl. Excellent engines and both ideal for your need. We have now used over 120 of the 2 cylinder models in the Albin Vegas all around the world and never a problem. Beta after-sales is fantastic as anyone will tell you. Cheers

 

[DGuthrie]

Maxi ~ There does seem to be an issue with the power output at the prop. I've been told that max prop size will effectively determine whether the engine should be 2-pot or 3-pot - in my boat's case, on this argument, 2-pot seems to be the limit. 13" is the maximum given the skeg configuration and allowing tip-to-hull clearance.
What's exercising my mind now is just that last point of Maxi's: reserve 'punch' against foul tide, chop, wind on the nose. I tend to the view that spare capacity is good, but if using it simply contributes to cavitation rather than moving water purposefully, then what's the point? If a larger capacity engine will return the necessary power with quieter running and less vibration, then okay.
Andy's point about the alternator's one I hadn't thought of - in fact, I didn't know the alternator could affect running in this way. I'm inclined towards something around 20hp, based on your comments so far. Trouble is, I'm also inclined to the Vetus guy; Vetus's next step after 16hp is 25hp! Back in the muddle! Nanni do a 21hp model. Beta do a 20. More muddle!
Comments still welcome!

 

[penultimate]

My feeling, having owned a K30S for many years is that 28HP is right but you will ordinarily only be able to develop a fraction of that with the small propellor. Have a word with Pete Johnson, our technical rep. for the K30. He re-engined with a Volvo and is very pleased with it.

 

[Searush]

How did you feel about your 33hp original engine? Was it too much, did it never get beyond low revs, or were you glad of the extra power sometimes with strong headwinds and dirty bottom? It probably wasn't producing 33 any more but it may help you decide if you need the extra grunt.

 

[patricmaude]

The main criterion for selecting engine power is governed by the propeller. A prop of a given diameter and pitch will only absorb a certain amount of power at maximum effective rpm. Exceed the max rpm and you get cavitation. Any engine power in excess of what the propeller will usefully absorb is wasted (although a margin for battery charging is useful). Assuming you wish to retain your existing prop, my advice would be to go to a propeller specialist and get his advice on engine power and rpm.

 

[sailorman]

try this

http://www.castlemarine.co.uk/pitch.htm

 

[Bodach na mara]

You have hit on the key factor: the prop. I had a Primose designed 28 ft Commando with a BMC Captain of about 30 hp. Above half throttle, the prop cavitated and ceased to absorb the power from the engine. That was a three blade 13 inch job. On Wight Dawn I have a 3 blade 16 inch diameter prop and the 27 hp engine struggles to give full power! One of our local surveyors takes the view that it is better to over-prop as it makes the engine work harder and live longer. It also gives more punch into a sea.

 

[WoodyP]

Been there, done that. (at great expense). I think the original engine fitted was the Sea Panther with a 24 volt start so there is a bit of extra wiring needed. The new engine cost £4294 inc in 2004 and took about 40 hours to fit plus parts and totalled half the value of the boat, but the comfort factor of knowing it will run when you need it is without price.

The old engine can be refurbished but you will still have a 30 year old lump.
We used the Beta 1005 28 hp, however if you read the blurb they only push out about 20 hp at normal revs.
It fitted well, runs like a sowing machine, good customer care, is much lighter, needed new engine beds (easy steel fabrication), comes with PRM 80 gear box but needed a new prop and shaft. Very happy with the engine, however the prop seems a bit smaller than the original which was nicked, and at full revs is more like an egg whisk than a prop. One thing to note is that the fuel pump on the Beta wouldn't shift the skin off a rice pudding and you will need new auxiliary inline pumps and filters on each tank to get the necessary lift.

We get about 6.5 kn max in flat or bumpy water, and it never faulters. Going into Wells Harbour in a blow when a smaller boat with a 10 hp engine had to be towed in over the bar convinced me that power in hand was worth having. Fuel consumption is light.

Penultimate is the Guru and membership secretary for the Kingfisher Yacht Owners association and his K30 featured about a year ago in PBO, so whatever he says goes, and I would point you to the website www.kyoa.org.uk . Join the owners association and you will get lots of helpful technical advice from Pete Johnson and two magazines a year.
JJ reckons they are "hard mouthed". Just reef a bit sooner and balance the sails. You made a good choice of boat. You will need to keep the boat a year or two to see your money back on a new engine though, unless you can do the job yourself or you find someone to work for less than £30 per hour.

 

[dickh]

I've just re-engined my Moody33 which was originally fitted with a BMC 1500 diesel which was 35HP at 3500 RPM but with a 1:1 gearbox - it would not rev above 1550RPM(with a smokescreen!). I also cannot fit a larger prop than 13" and that is with only ¾" hull clearance! Again the Nanni agent said I only needed 14HP but I opted for a Beta 25HP with a 2:1 gearbox and a 13x10 three bladed prop. It all works well but will only rev to 3200 RPM so am probably overpropped. I may have the prop re-pitched to 13x9 this winter so it revs to the maximum 3600 RPM.
One good thing with Beta was that they were the only supplier willing to make the mounting feet wider to suit my engine beds(£100 extra) thus avoiding making new beds - well worth the extra money.
I was offered a deal with a Yanmar from a boatyard in Wales which re-aligned the propshaft so a larger 15" prop could be fitted - which apparently works really well but at a price, and I would have to get the boat to Wales!
Go to the LBS and negotiate a good deal.

 

[Metabarca]

Concerning Searush's point, I recently re-engined my Centurion 32 (5500 kg plus baggage). I had a Volvo MD2B supposedly producing 27 hp and replaced it with a Volvo D1-30, maintaining the same prop and shaft. The difference in power at the prop (and speed) was staggering! So you may well find that a new engine with fewer horses than the old one will actually provide the same oomph. For myself, I have found that 30hp is more than enough for my boat, and probably something less would have been sufficient.

 

[Pye_End]

I would agree with much of this thread - start at the prop and work your way forward.

With a limited diameter on offer you rally need to look at shaft spped and gearbox reduction to give you the best power. I suspect that with just 13inch prop on offer then 28hp will be way too big.

The point about the alternator - it is not the size of the alternator necessarily that determines the load it puts on the engine, but how much power needs to go into the battery. It is rare for you to need to load the alternator for long periods - unless you are very power hungry, and are using the engine to replace lots of amps as much as using it to propel the boat.

 

[DGuthrie]

Steve Birch ~ Thanks for that. I am certainly considering the Beta 20 and 25hp.
Penultimate ~ Hello, George. I've been in touch with Pete and received sound advice to trawl the engine stands at LBS. Obiter dictum: I've just replaced the windows on Mercilla - would you like an article for the KYOA mag on this?
Woody P ~ already a member, thanks and see above. I'm certainly considering the Beta 20hp unit, or maybe the Vetus 25hp, depending on how this thread goes! Trouble is finding a local engineer to fit a Beta: their former guy is now the Nanni agent. His 28hp suggestion is in question and comes in at £4250, compared to about £3600 for the Vetus 25hp. Noted - and thanks - re: the lift pumps: may be a problem whatever I fit. I'd be interested in seeing pics of your K30, in and out: always looking for ideas to pinch. My e-mail's dguthrie@btinternet.com. Love to hear from you, share experiences. And yes, she's a fine boat, sails beautifully, well-mannered and steady; she'll see me out!
Pye-End ~ Thanks for the note about the alternator issue especially and on prop:engine size. More research clearly needed.
DickH ~ I think the Vetus can go in without much tooling around with the beds.
Kenjohnson ~ good point about working the engine: diesels need it, I understand.
And to all ~ I'm so grateful to you all for taking the time and trouble to respond to this thread. Much to mull over . . . and maybe more to come! It'll be an expensive round if you all take me up on the pint offer (ante)!