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Old 05-15-2007, 02:35 AM   #1
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Just as electronics and navigational aids have developed over the last two decades - equally propulsion systems for cruising yachts have changed.

In terms of power delivered to the propeller, inboard engines are lighter, smaller, quieter - more fuel efficient.

However, one of the downsides in the development of the engine has been the introduction of turbo charging to achieve higher HP output - which requires the engine to run at a higher RPM for the turbo to operate as designed.

Another negative for the the modern engine is that they are harder to repair - often having complex electronics.

I have friend who has recently acquired a 39' ketch built in the 70's - the original engine a Ford/Lehman, needs replacing as the block has developed a crack in a place which mitigates against repair.

His dilemma now is which engine should he choose to replace the old Ford.

The waterline length of his ketch is 34' - therefore max hull speed should be around 7.18 knots

(sq root of 34 x 1.34) He doesn't want a high revving engine to achieve the hull speed - but wants a good fuel consumption.

Suggestions on a good modern replacement would be very welcome ?
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Old 05-15-2007, 03:38 PM   #2
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I'm certainly no expert, but...

I've never repowered with anything much bigger than the horsepower recommended by the designer.

And I believe YANMAR is the finest marine diesel for my money.

Avoid marine diesels painted green.

Happy hunting,

Kirk
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Old 05-15-2007, 06:54 PM   #3
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I have repowered probably over 50 boats throught the years and there are many good diesel engines out there. I am a bit old school because I believe that low rpm engines, such as my Perkins 426, will last for many years. However I have used Yanmar, Volva Kuboto and others. Personally I like the Kuboto over the yanmar for the previously mentioned reasons. However, I installed several Cummins small 4 cylinder engines, I forget the model, but it is not an engine manufactured by Cummins but marinized by them. It has 65 hp@ 2600 rpm but even better it rates at 55 hp@ 1800 which should give it long life it also gats excellant fuel economy. This engine is available from Transatlantic Diesel in White Marsh Virginia. Call Marcus Neville and get the info, its a good powerplant nd should fit the 39 footer perfectly. Remember, regardless of the engine used be sure that the installation is done correctly and that you keep clean fluids in any engine for long life.
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Old 05-15-2007, 07:52 PM   #4
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I can only recommend that he stay with the Ford Lehman.

http://bomacmarine.com/ford-lehman-engines.html

It lasts forever if maintained and is the easiest engine in the world to work on or find replacement parts. IMHO of course.
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Old 05-15-2007, 10:49 PM   #5
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I agree with the principle of keeping it simple. The best engines I ever encountered in boats were a Perkins 4108 and my current GM353 which....KIRK....is painted GREEN (although a slightly different hue to V green). It does like a smoke every now and again, and you certainly know when it is working because it shouts at you...but it's a tank engine.

David
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Old 05-16-2007, 12:17 PM   #6
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Quote:
Originally Posted by Gallivanters View Post
...Avoid marine diesels painted green....
What's the deal on engines painted green? What color green is the bad color??

thanks,
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Old 05-16-2007, 01:10 PM   #7
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Despite their excellent performance and the genuine reliability of their truck and car engines, it seems that somewhere along the way, Volvo marine diesels have earned themselves a poor reputation. They are painted green.

I would make the point however, that in a previous boat I had a 4 cylinder, 45hp Volvo which was as good, quiet and reliable as any engine I had encountered. I am also a little biased as 5 of the previous seven new cars I have bought were Volvos and I love 'em.

David
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Old 05-16-2007, 10:54 PM   #8
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Quote:
Originally Posted by atavist View Post
What's the deal on engines painted green? What color green is the bad color??

thanks,
I've sailed with a " green painted" 1975 model Volvo MD6A 2 cylinder fishing boat type engine all these years..... The devil is soild heavy cast iron and is easily hand started. It has taken much abuse and if it ever let me down it was usually on my part for having a brain fade or skimping on maintainance.

I was talked out of replacing it with a new Yanmar 3 years ago while in Coff's Harbor by an older gentleman mechanic. He said "They don't make them like that anymore " but was willing to take my money for the new Yanmar. Following the philosophy of "Know the devil you own" I had him rebuild it. I'm very happy with the work done and will probably get many more years of use as I found it is still easy to get parts for it.

I use to go through so many Johnson Pump water impellors until I discoved the "blue" impellors as manufactured by Globe in the US. No worries now!

One irritating item, from the past and present.. it still has some traces of smoke flowing out the exhaust even after the total rebuild on the engine and injection system. Sounds familiar?
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Old 05-16-2007, 11:09 PM   #9
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"Know the devil you own"...so true!

I can't imagine leaving on a long distance cruise without knowing that I can completely dismantle my engine and rebuild it on my own. Prior to having done so, an engine failure always worried me more than even the worst weather.

Replacing a low RPM workhorse with a turbo-charged Asian spinner makes no sense to me.
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Old 05-25-2007, 02:44 PM   #10
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Volkswagen Marine Diesel

http://www.frenchmarine.com/ProductsM.aspx?CID=0&MID=21

Interesting entrant into the marine diesels market?
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Old 05-26-2007, 06:44 AM   #11
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We have been looking at the Lagoon 420 and it has the electric motors which run on a battery bank and have a genset for charging batteries. In fact as you are sailing and the props turning it regens the batteries on its own.
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Old 05-26-2007, 08:45 AM   #12
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We have been looking at the Lagoon 420 and it has the electric motors which run on a battery bank and have a genset for charging batteries. In fact as you are sailing and the props turning it regens the batteries on its own.
----------------------------------------------------------------------------------------------------------------

As a Multihuller myself , I have always been interested in alternative power to that provided by individual diesel engines in each hull.

My first Catamaran I had built in Brisbane Australia, this had a single 80 Hp diesel engine driving a hydraulic pump which in turn drove a Cesna aircraft hydraulic motor in each hull - these driving folding props.

The the earlier Lagoon 42's when fitted with diesel engines had 2 x 28 hp motors - the equivalent of 2 x 21 Kw.

The Lagoon 420 that you are looking at has 2 electric motors rated at 10 Kw each

(= 13 Hp each) The generator to power the batteries produces only 11 KVA .

Ask yourself what size battery bank will you require to produce 20 Kw for the motors ?

How much electrical power will the propellors deliver when under sail ?

How much drag do non-folding propellors produce?

If the Lagoon is cruised in tropical waters - where the propulsion system will be in use at least

60 % of the time - that generator will have a tough time.

The Lagoon 420 has a lot of windage and at 15 tons loaded - my own experience tells me that

her hybrid system may not be able to cope, when running into strong head winds coming out of a line squall.

However, the concept has merit - even though perpetual motion is still not round the corner
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