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Old 25-07-2008, 14:28   #1
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New engine

My engine had decided that water is a much better lubricant than the nice engine oil I was feeding it. It also has a noisy gearbox that the surveyor felt this was due to a worn bearing. To get at the gearbox requires sliding the engine forward. I am in Croatia and it is very difficult to find mechanics I would trust with an engine rebuild where it is not possible to supervise the work.
I am still exploring the possibility of replacing the head gasket (hopefully this is the problem rather than a cracked cylinder head ) or even adding a sealant (steel seal) to the water as a stop gap measure. My preference is to fit a new engine as I am likely to be in the south pacific in a few years and want something ultra reliable.
The existing engine is a Nanni 5.280 62 hp model which is no longer made. I am not sure how well this powered the yacht (LOA 14.56m centre cockpit aluminium boat Displacement 14.5T) because the Tachometer was reading incorrectly. (I have not managed to locate an optical tachometer yet). The yacht has a Maxiprop and would only do 5 Knots at an indicated 2300 rpm. I think the 2300 was incorrect, but as it was possible the Maxiprop had been adjusted to too fine a pitch I was not willing to push the revs higher until I had calibrated the Tachometer.
The Yacht sails beautifully even in light air, so I rarely motor and the limited speed under power was not a great problem but now I need to think about a new engine.
My choices, that ,are as follows
A Yanmar 54
A Yanmar 75
A Beta 60 (58Hp)

I think after careful measurement the above three engine will fit. My preference is for a Yanmar 75 but the exhaust diameter of the existing engine is 60mm and a reasonably long (because it is a centre cockpit) but smooth run. Both Yanmars (54 and 75) specify a 76mm exhaust . The exising exhast trvels trugh 60mm muffler hose to a water trap to a swan neck and exits through a 60mm 2m long pipe that goes through a watertight collision bulkhead and exits above the waterline. It will be difficult to fit 76mm hose in the existing space and very difficult to to increse the diameter of the 2m pipe.
assuming the exhaust system is not upgraded is it still viable to fit the the 75 hp Yanmar (a turbo charged engine) or do I need to drop down to the 54hp Yanmar or is even this unsuitable for the exising exhaust ? Would your advce vary if I can upgrade the flexable hose to 76mm but still leave the 2m pipe at 60mm ?
The Beta 60 only requires a 50mm exhaust but the delivery time in croatia is very long and my prefrence is for the Yanmar if it is OK.
What sort of performance can I expect with a 54hp motor in my boat. I would be quite happy to motor at only 6 or 6.5 Knots but it would be nice to still make some forward progress under motor if my anchor drags in 50knots of wind.
I have emailed the Yanmar dealer here and he has replied that the 75hp should be fine with a 60mm exhaust but goes on to say that excessive backpressure can cause burnt out exhaust valves!
Sorry for so many questions in one post but I have found this forum gives some great advice and I need some of that now.
Cheers John
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Old 25-07-2008, 15:03   #2
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Without getting into the technical issues of the exhaust and just comparing our boat that has a 63 HP Westerbeke and the boat being 11 meters and 9 tons displacement. I would say we are only slightly over powered. The Westerbeke was set up to cruise at 2000 rpms. At 2400 in heavy chop it punches through at 6 knots or better. I really don't get extra speed at 2400 unless there is chop. With your extra length and weight I don't see the 75 HP being over kill at all. I would calibrate the prop pitch since getting the max rpms at full would set it to the best pitch or at least close enough. Our last boat was over pitched and the last owner trashed the tranny with a prop that was too big. I was lucky and got a new tranny as part of the survey but it took a while to figure out the prop problem.

The difficulty of the exhaust seems to be not insignificant but I'm not sure it voids the idea of a power system able to do at least on paper more than you can now and instead actually be less power. In our prior boat we had less power than optimal and it shows up in choppy conditions where sailing becomes difficult and motoring is required. I always found those times motoring head to wind into heavy chop very difficult as the bow would bounce and dissipate all the momentum.

Our transom has a drop section that prohibits a rear exhaust. Our exhaust goes out the side. I guess I would explore exhaust options before giving up. Having to replace the engine and transmission plus all the attached components is a serious job with a high cost. I think you should want to have a better boat at the end of the job given the time and money involved. I can't see 75 hp as being too much.

I would love to be able to suggest a super mechanic in Croatia but I can't. Perhaps someone can suggest some place you can sail to in a reasonable time period. We have members seemingly everywhere. I know it's a lot of work and some qualified help is going to matter. Were you here I know a guy.
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Old 25-07-2008, 15:54   #3
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The Yanmar exhaust requirements were one of the reasons I chose to repower with a Beta 50. In flat water with a 3 bladed Maxiprop, the Beta pushes my 14M, 14T (as loaded for cruising) Beneteau at 8 knots. Peak RPM is 2800, and the boat cruises at 6 knots at 1900 RPM. The old Perkins 4108 was good for less than 40 hp, but it would make headway into into 50 knots in protected water.
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Old 25-07-2008, 15:59   #4
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consider Volvo also
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Old 25-07-2008, 16:05   #5
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I have the yanmar 4JH4E (54hp) on my 12.6m (41') 21.5 pounds displacement. Also have the max prop. When I put the engine the prop was at one setting. I got as much as 7.75 knots out of her. I cruised at 7.25. When I pulled it out over the winter I reset to the recommended setting and the performance suffered. Speed is lower and fuel consumption is higher. I would imagine that 1/3 less weight and 2 extra meters of waterline would make the boats pretty even. I would avoid the turbo charger b/c of the complexity. I don't know wha to say about the exhaust b/c I bit the bullet and upgraded those as well.
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Old 25-07-2008, 16:55   #6
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Thanks for all the replies and keep them coming. Information on performance (cruising speed and performance in high winds) is especially useful in helping me make a decision .
Just to clarify the statistics of my boat it is 14.5m long ( 47.5 feet) with a displacement of 14 tmetric tons (about 32000 lbs) I should have quoted the imperial figures. I tend to think of boat length in feet but displacement in Kg !!
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Old 25-07-2008, 17:15   #7
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I'm surprised at how much power the responses have in their boats! I'm currently replacing a Perkin's 4-107 (40hp) with a Beta 38 (38hp) on my 14t displacement ketch. The Perkins drove her easily at hull speed so I couldn't see any reason to go higher, and didn't find any diesel salesmen or mechanics pushing me higher either. Seems overpowering just adds weight and burns more fuel. Up here in the PNW I also have strong currents to contend with, and the Perkins did just fine with them.

BTW - I opted for the Beta after narrowing down the choices from just about everything mentioned plus a few more. Final choice was between the Beta and Yanmar, and I opted for the Beta primarily on price. I couldn't get anyone to deal on a Yanmar, while Beta (SoundMarineDiesel.com) gave me a nice discount and were very helpful. I also found my friends in the marine trades couldn't get better Yanmar prices even for their own boats.
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Old 25-07-2008, 17:20   #8
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Quote:
Originally Posted by noelex 77 View Post
Thanks for all the replies and keep them coming. Information on performance (cruising speed and performance in high winds) is especially useful in helping me make a decision .
Just to clarify the statistics of my boat it is 14.5m long ( 47.5 feet) with a displacement of 14 tmetric tons (about 32000 lbs) I should have quoted the imperial figures. I tend to think of boat length in feet but displacement in Kg !!
using your specs and assuming a 40' waterline. The Volvo engine configurator point to 75hp.
I have only good things to say about the 4JH4-TE and the Volvo D2-75. Either would be an excelent choice.
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