[Public-list] diesel engine

[Don Campbell]

We are back to power and props . There is an optimum prop for every motor and
the rules of thumb for this is 1" of diameter is 2.5" of pitch and 2" of pitch
will change the RPM by 450. Match the prop to the performance curves - Torque,
HP and fuel consumption - to fit the motor not the boat or skipper. The hull
speed of an Alberg 30 is about 10.5 feet per second.
    A more recent comment talked about having more HP in reserve for times when
needed. This is pointless if the power cannot be transferred to the prop. You
need to consider effective thrust on the prop not HP in reserve. And the boat
will still only go at 10.5 feet per second. (The spec on the A4 from dynomometer
tests is that the motor will put out 36 HP at 3600 RPM. Effectively we can only
get to 2000 RPM in our application. We have power in reserve but of no use.)
Diesels run most effectively and efficiently when they are at the peak of the
torque curve and  with a constant load. Thus, they should be run at that amount
of throttle regardless of the sailing conditions so again the effective HP is
decided by the design of the motor. Using a diesel at less than optimum will
only carbon things up.
    As Gord says "Why do we need a diesel"!! I would contend that it is only
needed if one needs to extend the motoring range of the boat and in that case
consider a trawler. On the other hand, if the current gas engine has worn out,
then it is an alternative that is worth considering, since no-one seems to be
using small, gasoline inboard engines for marine applications these days.
Don  #528

"sousa, stephen (ENG)" wrote:

> We have a Yanmar 13 hp and see the same as other folks for performance and
> fuel usage. Will the 11 hp push an Alberg, sure it will. The other question
> is what type of gear reduction did Universal use with this motor.
>
> Lee what is the hp of the Volvo currently in your Alberg? This will give you
> some type of comparison from the Volvo which is X hp to an 11 hp. IMHO from
> reading about boats similar in size such as a Baba 30, the prop on the
> Alberg could be larger than what we have for a diesel application, taking
> into account when the boat was designed the spec was an A4 or Grey with much
> more horsepower. It would be great if we could put a 14 inch machine pitch
> wheel on this boat, it would take quite a lot of work with limited payback.
>
> Stephen
> #114
>
> -----Original Message-----
> From: public-list-bounces at alberg30.org
> [mailto:public-list-bounces at alberg30.org] On Behalf Of Richard Mair
> Sent: Wednesday, February 02, 2005 7:40 PM
> To: Alberg 30 Public List -- open to all
> Subject: Re: [Public-list] diesel engine
>
> We have a Renault RC8D engine. This is a single cyl 8
> hp diesel. Two blade 13 in prop(i forget the pitch).
> On flat water we get just under 6 knots.We usually run
> it at about 5 knots if the wind dies and we have to
> get home..If there is wind it stays shut down. Used
> 1/2 the 12 gal. tank for the season using the boat
> every weekend and on wednesday night racing    Richard
>                                                   ---
> FINNUS505 at aol.com wrote:
> > Does anyone have an 11 hp diesel engine in an A30,
> > and if so, does it get
> > the job done?
> > Thx,
> > Lee
> > Stargazer #255
> > _______________________________________________
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> >
>
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