Josh Assing wrote:

How do I find this information?


From the engine manufacturer... AND/OR, if you give us all information
about your boat & engine, there are people in the NG who can pull their
attention away from politics & back to boating long enough to impart
some good advice, even some expert knowledge...!

Rob




On Thu, 26 Aug 2004 16:58:34 -0400, "IBNFSHN" wrote:


To properly prop your boat you need to know what the WOT (wide open
throttle) range is for your motor. Then you need to know what RPM you now
turn (with a normal load) at WOT. It is usually just a matter of adjusting
the pitch up or down.



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I believe it should be 4200-4600 rpm.

--
Bill
Chesapeake, Va


"Josh Assing" wrote in message
...
The recomended rpm's (high end) will be with the manufactures
documentation. If you don't have it you can get it from whoever made the
power plant.

Thanks -- I'll try to find them -- it's a mercruiser mcm 5.0litre
"AlphaOne"
engine

cheers!
-josh

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Josh Assing wrote in message . ..
Prop pitch is somewhat like gearing in a car. If you pull more
(skiing) you need to gear down (lower pitch prop) giving you more
torque and less topspeed.

Hmm. I put a wrong prop on my fiberform years back and it just caused the boat
to "go fast" at idle; but at 1/2 throttle; it'd overheat & never go "faster"....
that's why I thought it was all designed "together"

There are limits ... there will be a few pitch and prop sizes that
work with your boat and different load condiditons.... others will not
make sense.

If you are cruising with a light load you dont need lower gear/pitch
and can have a prop with high pitch and go faster.

and theoretically better fuel economy?

Yes versus using a prop with very low pitch with a light load.


Getting the right prop and the right prop for the day/application can
be quiet the quest...

hmm. well; hopefully there's other Larson owners out there that can help....


has nothing to do with the brand, rather with HP, gear ratio, boat
shape and weight.

Matt

Josh Assing wrote in message . ..
The recomended rpm's (high end) will be with the manufactures
documentation. If you don't have it you can get it from whoever made the
power plant.

Thanks -- I'll try to find them -- it's a mercruiser mcm 5.0litre "AlphaOne"
engine

If its this motor:

5.0 MPI - 260 HP


Then WOT=5000 rpm

att

Josh Assing wrote in message . ..
Thanks.

Now I just gotta figure out what the RPM range is & all that jazz.
I'd rather have better top end & fuel economy...

RPM ... see my other reply...

If you do skiing then you should keep the low pitch prop on there. If
not get a prop with normal pitch for this boat.

With a propeller boat you might want to have 2-3 different props for
different uses and put on the prop for the day, depending what you do.

(One spare with tools to put it on should be in the boat)

Matt

I have a 18Sei w/ 3.0 Litter. Came with a 17 inch. Too much throttle left.
19 is perfect. 21 was too much.

Mike

"Josh Assing" wrote in message
...
We just picked up a larson power boat - the PO said it had a "ski prop" on
it;
but if we put the "stock" prop on; the boat would be faster....

I don't know much about props; but I thought props were 'designed' for
engine &
boat -- and couldn't (shouldn't) be swapped about....

is this true? if so; what should the proper prop be for the boat?

Thanks
-josh


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activities... I think you need to do some in depth research on prop
selection and not limit yourself to "21' Larson" owners...


agreed; but a base to start from would be helpful; especially since it's out of
the water right now...


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From the engine manufacturer... AND/OR, if you give us all information
about your boat & engine, there are people in the NG who can pull their
attention away from politics & back to boating long enough to impart
some good advice, even some expert knowledge...!

Thanks.

found out that the engine is rated for 4200-4600 rpm at WOT. It left the
factory with a 14.5x19 prop (3 blade) it currently has a 20pitch 4 blade. it
tops out at like 35; but the data I've found said the boat should reach 45-50.


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Thanks -- I'll try to find them -- it's a mercruiser mcm 5.0litre "AlphaOne"
engine

If its this motor:

5.0 MPI - 260 HP


Then WOT=5000 rpm

5.0 mmc -- mercruiser said it's a 200hp & 4200-4600

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I planned on putting this prop in the boat for "spare" -- but I want a better
"all around" prop for day-to-day usage -- as we plan on leaving it in the
water...

On 27 Aug 2004 12:30:27 -0700, (Matt Lang) wrote:

Josh Assing wrote in message . ..
Thanks.

Now I just gotta figure out what the RPM range is & all that jazz.
I'd rather have better top end & fuel economy...

RPM ... see my other reply...

If you do skiing then you should keep the low pitch prop on there. If
not get a prop with normal pitch for this boat.

With a propeller boat you might want to have 2-3 different props for
different uses and put on the prop for the day, depending what you do.

(One spare with tools to put it on should be in the boat)

Matt


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