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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance > Engines > Diesel
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Diesel This is a new forum dedicated to diesel engines and their applicable accessories.


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  #1  
Old 10-24-2010
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Repowering a motorsailer

Howdy all,

We've just bought a 40ft steel motorsailer project with 2 x Perkins 4108's in it (900 hours a piece). The boat has twin props, twin controls and excellent access to the engines, and weighs 40,000lbs (19 tonnes).

I've read somewhere that these engines:

- continuously leak oil
- are rated at 50hp, but only deliver 25hp at the prop

Now, access under the engines isn't brilliant and being a steel boat, this is a problem for us. I'm also a fan of simplicity and would like to reduce the x2 of everything.

So.... thoughts on repowering? We were thinking a 75hp Penta or Yanmar would theoretically do the same job as both Perkins, plus increase access and storage space. Yes, we'd need to blank off the current prop shafts and add a new one but this is all quite do-able in steel.

For the guys that have done this or know bigger boats with bigger engines, does all this sound feasible?

Thanks in advance.

cheers,
nathan
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Old 10-24-2010
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The first thing that comes to mind is, why? 900 hours is nothing for those engines and unless they have problems they should last a long, long time. The boat was apparently designed for twin screws so I would think long and hard before I tore them out. There is an argument for simplifying things, but then again there is a good argument for redundancy. Have you actually operated the boat much, I'm wondering how much you would miss the ability to turn in it's own length versus typical sailboat handling which is generally pretty terrible? Just my initial thoughts without knowing any particulars.
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Old 10-24-2010
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Ausnp,

Agree with JRD, I had a 36 foot heavy displacement boat
with a fair amount of windage, single screw. It was a handful
when docking in cross winds, many a time I wished I had twin
screws. Even in steel, converting to single screw sounds like
a massive project, new log shaft and rudder, possible re-configuration
of the keel, and what else?. In addition to the docking advantages
having two engines and charging systems would seem good to me.
The boat was designed for two engines, changing could possibly
upset the overall balance and performance? If you want different
engines for whatever reasons change them out. If it was my boat
I would stay with two engines.

Just my two cents worth, Dabnis
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Old 10-25-2010
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Quote:
Originally Posted by dabnis View Post
Ausnp,

Agree with JRD, I had a 36 foot heavy displacement boat
with a fair amount of windage, single screw. It was a handful
when docking in cross winds, many a time I wished I had twin
screws. Even in steel, converting to single screw sounds like
a massive project, new log shaft and rudder, possible re-configuration
of the keel, and what else?. In addition to the docking advantages
having two engines and charging systems would seem good to me.
The boat was designed for two engines, changing could possibly
upset the overall balance and performance? If you want different
engines for whatever reasons change them out. If it was my boat
I would stay with two engines.

Just my two cents worth, Dabnis

Fair points - our biggest concern was the inherent Perkins leakiness and extra space that may be gained by only having a single screw, but having tried to dock a 34 footer before with a single, having two would definitely be much easier.

If we were going to stay with the two then and wanted to repower, Universal? Yanmar? She's a heavy boat that won't use the engines much but when they are required, they'll be put to hard work (European tides). Any standout manufacturer we should be looking into?

cheers,
nathan
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Old 10-25-2010
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Ausnp,

Are the engines leaking now? Perhaps you could put some time
on them under load to see first hand how they perform and observe
any potential problems both inside and outside of the engines?
Although I haven't done a re-power I have read it is not something
to be taken lightly, both from a time and money aspect.

Dabnis
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