Swan 47 - new engine

I'm thinking about a new engine for my Swan 47/51 Djata, replacing the old Volvo MD21A. Any suggestion, information or experience will be of great help to me. I am especially concerned about the works to do with the engine room, the shaft, the propeller, ... .

Thanks, Marco

I'm thinking about a new engine for my Swan 47/51 Djata, replacing the old Volvo MD21A. Any suggestion, information or experience will be of great help to me. I am especially concerned about the works to do with the engine room, the shaft, the propeller, ... .

God morning Marco,

I happen to be doing just that. Putting a new engine in my 47. Here are my considerations, hoping it will help you sort out some of the many aspects:

1/ Engine size and power: Looking at the fittings (the feets) and the dimensions, the most suitable appear to be the Volvo D2-55. But, it is rather small in terms of power. There are of course other brands tha can also almost fit but the majority will necessitate some work on the engine bed. Adding to that the fact that the space, although long, is not wide enough to allow extravaganzas.

2/ I opted for the Volvo D2-75. It is a little more powerful and it is modern and has this new one wire connection to all kind of instrumentations. It can even send the data to a computor! Now, what are the problems:

- The engine bed must be addapted a littel. Some stainless steel plates of a good dimension with some driling and welding will do the trick.

- The new engine being shorter that the old MD21, it will be fitted as aft as possible, liberating space in the front but necessitating some work to fit the gear box.

- Thus the need of getting a new longer shaft.

- Since I have an excellent maxprop that I wich to keep, I have ordered the new shaft in the same configuration as the old one: 11/2 inch diameter and the corresponding cone to my maxprop.

- My actual Maxprop, that I am keeping, is 21 inch (533mm). In order to obtain the best output from it, it is necessary to choose the right reverse/gearbox. Luckily Volvo gives different choices. The suitable one is the MS25L Mechanical Drop Centre with strait output. The advantage of this is that you can decide if you want a left hand or a right hand rotation: The same gear box above can do both: 2.27:1 Right hand and 2.10:1 Left hand. This will give you excellent adjustments possibilities. In my case, because of the size of my maxprop, I need to go for the 2.10:1, thus fitting the maxprop rotating left at an olmost optimal Alfa angle of 20 degree. The result will be that the engine will rotate at about 10% under its maximum capacity, that is 2700. According to Volvo people, this is optimal.  

I hope that this thoughts will contribute to your own thinking in this matter.

Good luck/ Philippe

I'm thinking about a new engine for my Swan 47/51 Djata, replacing the old Volvo MD21A. Any suggestion, information or experience will be of great help to me. I am especially concerned about the works to do with the engine room, the shaft, the propeller, ... .

Dear Marco,

I changed the old MD for a Yanmar 100 HP Turbo. No big deal! Of course the frame has to be rebuild, new and longer shaft. The intrance to the engien room from the aft cabin has to be rebuild too, original one do not give room enough for the turbo. Etc. Fantastic power and feeling in manouvers.

Marco, I now have a Nanni 85hp in my Swan 47CB. The Nanni engine is based on the Kubota digger engine which has a good reputation and it has 5 cylinders which makes for very smooth running when compared to a big 4. I didn't do the work, but the old hydraulic gearbox was retained as was the two bladed Max Prop. The engien is lower revving than some with 2,800 as max and our usual cruise is 2,000 which is quiet and smooth.

In all the Nanni is a very good engien and I'd recommend it. My long standing engineer also sold many into the UK and is very familiar with maintaining them which is a bonus.

You have some good choices. Gavin

I have two altenators including a 140 amp one for the service power.