[Public-list] Propeller question

Mon Feb 13 10:31:33 PST 2006

is your prop a 2 or 3 blade prop? Who made it? Thanks for the info.

>>> bob at fox.nstn.ca 02/13/06 1:01 PM >>>

Hi John,

What you "may" need as was recommenced at a "Seminar on Boat
Electronics"
that I recently attended is to change the voltage regulator in the
alternator to an External Marine regulator.

Anyone ever heard of this?
They can be adjusted to slightly vary the voltage.
You have to be careful varying the voltage so you don't cook your
batteries.

The operating voltage area or envelope we operate in is very small and
it
does not take much to cause problems. 
Without going into a detailed explanation about the difference between
a
regular "auto" voltage regulator and a "Marine External" regulator, you
may
want to look in to this.

I changed my 13 X 7 prop on my Atomic 4 to 11 X 7 and had it balanced.
I would rather have gone to a smaller change of 12 X 7 but the prop was
in
bad shape on the ends, it was cheaper to cut the ends off and reshape
and
balance at the time.

The engine now runs at 1800 rpm in flat water at 6.2 knots.  The engine
also
comes up to higher rpm a little faster than before but this does not
help
charging the engine that much.

I have 2 batteries:

One deep cell (house bank) and one regular truck starting battery.
Deep cells discharge slowly, and take longer to recharge, than regular
batteries. This is why a Marine External Voltage regulator is better
for
boat setups.

Another problem is that we just don't run the engine that much, we go
sailing!
That is another reason the batteries don't get charged much!

If you have the original wiring harness on you Atomic 4 you may want
to
change a bit of it. The charging side especially. The large orange and
red
wires in the rubber plug near the engine.

My boat had an Amp meter in the engine panel and I changed it to a
voltmeter
and I replaced the wiring on the charging side of the circuit.

In order to have an amp meter (amp meter must be "in series" with
charge
current) in your panel the wire runs all the way up to one side of the
Amp
meter and back to the engine. There can be a voltage drop in this
setup.

Some say go to a higher rate alternator, especially if you have one of
the
old 35 amp alternators. This is an option as was discussed at this
seminar
but the instructor recommended the advantages of External Marine
regulator.
He also recommended changing the wiring to a more modern
configuration.

The instructor gave out wiring diagrams and if anyone is interested, I
could
scan and email them.

I hope this was not too long winded...

-bob
#560

-----Original Message-----
From: public-list-bounces at alberg30.org
[mailto:public-list-bounces at alberg30.org] On Behalf Of John Boor
Sent: Friday, February 10, 2006 5:09 PM
To: Alberg 30 Public List -- open to all
Subject: Re: [Public-list] Propeller question

I too have a 2 blade prop that max's out at 1400 RPM and
find this is to low speed to recharge my battery bank
quickly.  I am haveing my prop re worked to reduce the dia
to about 11 ins and decreasing the pitch a little.  This
will have the effect of increasing the RPM's to about 1800
at 6 knots thus allowing my 90 amp alternator to deliver
full amps, also it will let the A4 work in a better power
range.  I thought about the Michigan 2 and 3 blade prop's
but neither would increase the RPM's I need.  I hope this
will improve my performance but only this summer will let me
know.

John Boor
MAHSEER #380

 I am  interested in upgrading my propeller. The boat came
> with a 2 blade
> 13-6  sailor prop. I have an A-4 with a 1:1 gerar ratio.
> The engine seems to max out at about 12-1400 rpms at about
> 6 kts, if memory serves
> me correctly. I want to go to a 3 blade sailor prop to
> improve the thrust and maneuvering capability, especially
> near the dock.  Michigan Wheel recommends a 12-6 three
> blade prop based on the data I provided in
> their prop-it- right web survey.
> 
> 
> My questions are - what sort of rpms do you get if you
> have a three blade sailor prop coupled with an A-4 having
> a 1:1 gear ratio. What size 3 blade prop do you have?
> 
> What are other sources for props - aside from Michigan
> Wheel? 
> 
> Any other reflections or observations would be
> appreciated. 
> 
> Thanks
> 
> David #432
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