new Diesel engine?

Hello,
I bought a very old boat. And now iam looking for a new engine.
But I do not know how much power I need.
How can I find the propeller size?

Can you help me to find some books or internetpages about this?

Leo

"Leonhard Fischer" <lfspamer DeleteThis @gmx.de> wrote in message
news:efdmlg$45s$01$1@news.t-online.com...
> Hello,
> I bought a very old boat. And now iam looking for a new engine.
> But I do not know how much power I need.
> How can I find the propeller size?
>
> Can you help me to find some books or internetpages about this?
>
> Leo
>

Unfortunately you do not give us enough information and even if you have
found that a good deal of experience is needed top get the optimum answer.

We need to know such things as :

Type of hull (displacement, semi-displacement, or plaining) and your
projected speed. There is no point in installing an engine powerful enough
to put a similar sized boat up on then plane if you have a displacement
hull. Likewise if this was an UK inland boat where strict speed limits apply
there is no point in installing an engine that is so powerful it never gets
off idle.

Water line length and possibly weight.

Type of water it is to be used on.

Once you have this information a look at brochures for new and second-hand
boats of similar specifications will give good idea about engine power
required.


Having got the power you can then start thinking about the propeller. For
this we need to know:

Hull shape or make of production boat

Water line length and possibly the beam.

Weight

Diameter of prop that can be swung (leaving a 50mm gap between prop tip and
hull/skeg).

Engine torque curve or engine make.

Gearbox reduction ratio

If you want speed or economy.


I normally advise that a prop specialist is consulted, but it is all a
matter of compromise and you do have to know about the engine first. The
other way to do it is to explain it all to a prop specialist and see if they
will estimate the power required to meet your needs.

However power is not the issue, Torque is. A planing boat may well need a
high revving engine matched to small props, where as a displacement boat
could do with a large prop coupled to an engine that provides maximum torque
at lower speeds.

More info please.


--
Tony Brooks
www.TB-Training.co.uk