[MHml] thrust

[Dave Culp]

Y'all know that "9.9" hp is the most variable class of outboards there is,
right? They vary from 7-8 to well over 15 horsepower, depending. The reason
they're "rated" 9.9 is that's the max for many reservoirs.

Dave

On 2/6/07, Paul Nudd <paulnudd at actionpotential.com.au> wrote:
>
> Martti Halminen wrote:
> > Bill Gibbs wrote:
> >> Let's move on to the topic of outboard thrust in pounds.  Does anyone
> know how much thrust a 100hp outboard produces?  Or a 200 hp
> >> outboard?
> >>
> >> Order of magnitude guesses would be a help as I have no clue.
> >
> > As an upper limit, a rule of thumb for bollard pull of harbour tugs:
> > without Kort nozzles, one ton per 100 hp.
> >
> > This is with correctly dimensioned, large, slow-running propellers, so
> > for an outboard the ratio is certainly worse.
> -----------------------------------
> Of course thrust will vary with speed.
> The harbour tugs will not achieve 1 ton/hp at 20 knots.
> An outboard set up for 1 ton/hp at 20 knots will not give much at 0 knots.
> To drive AB at 20 knots is one thing, to accelerate AB from 0 to 20
> knots is another. Perhaps a variable pitch is required.
> Also the hp claims for outboards are highly variable and do not give a
> reliable indication of the thrust.
> A thrust curve (thrust/boatspeed) for a particular
> engine/gearing/propellor combination is what is needed to match up to
> the thrust needed curve (thrust/boatspeed).
> Joe Siudzinski posted a while ago some real world bollard pull figures
> for the yamaha 9.9 available on his website:
> http://www.instantweb.com/s/siudzinski/Cruise/KatieKat2003E.html#050503
> PN
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