[Public-list] Atomic 4 compression

[Mike Lehman]

Yeah but you are running through a 2:1 reduction gear. The Atomic 4 is 
direct 1:1 drive. 1400 is about right for the A4, although you can reduce 
the pitch/diameter of the prop to get more RPM if you want.



Mike Lehman
~~~_/)_/)~~_/)~~~




----Original Message Follows----
From: "J Bergquist" <jbergqui at gmail.com>
Reply-To: Alberg 30 Public List -- open to all <public-list at alberg30.org>
To: "Alberg 30 Public List -- open to all" <public-list at alberg30.org>
Subject: Re: [Public-list] Atomic 4 compression
Date: Sun, 9 Jul 2006 22:02:36 -0400

I have a 13x8 2 blade with a Beta 16 HP diesel. I can run right up to 3000
RPM. I have not measured speed because my speedo has never worked, and my
GPS is also not working at the moment, but it appears that I can't go any
faster than what I get at 3000 RPM. The boat throws quite a wake at that
speed.

Glad to hear you got your motor sorted out. I know how much it sucks futzing
around with the motor on a sailboat. I'd much rather go sailing...

Later,

J

On 7/9/06, Brian Palmer <Bpalmer at digitalarsenal.com> wrote:
 >
 > Thanks everyone for all the tips and advice.  I tried a number of things,
 > and this evening, I hit the last of the items that was causing the poor
 > performance.  Here's a brief run-down:
 >
 >
 >    - I checked compression for all the cylinders: 110, 108, 105, 110
 >    - re-gapped the plugs to 0.035 (they were set to 0.030)
 >    - I took the carb apart and cleaned it out, changed the gaskets, and
 >    realized I didn't have a good seal on the larger of the two gaskets
 > because
 >    the two cast aluminum halves are not machined perfectly flat... So 
with
 > the
 >    gasket in and bolted tight, I could see some light through the other
 >    side.... I used some permatex on both halves to assure a good seal.  I
 > was
 >    thinking this winter of taking each half, and running them over a flat
 >    surface with some wet/dry sand paper to try to true up the
 > surfaces.  For
 >    now, the Permatex does the trick.
 >    - Cleaned the prop
 >    - And the last thing that seemed to make the big difference.. I
 >    disconnected the fuel line and pumped fuel into a clear container and
 >    realized I had a fair amount of water getting through my Racor filter,
 > which
 >    I just emptied yesterday.  Turns out I had about a pint or 2 of water
 > at the
 >    bottom of the tank, and my model Atomic 4 engine apparently needs gas
 > to
 >    run, not water!
 >    - After pumping several gallons of gas in a container, letting the
 >    water settle, pouring the gas back in the tank through a water
 > separating
 >    funnel, and then pouring the last bit with all the water into a
 > disposal
 >    container... Finally I could pump fuel that was coming out water free.
 >
 > I took the boat out for a spin, and she now does a solid 5+ knots at
 > 1400RPMs.  I think I can't go higher RPMs because as I recall, I have a
 > 12x7
 > 2 blade prop, which I'm told is a bit too steep of a pitch for the 
engine,
 > and is bogging it down.
 >
 > The engine just feels much more steady and powerful, and  the throttle
 > feels
 > predictable, and I can run without the choke on at all.  What a
 > difference!
 >
 > Just curious, What size and pitch props do you all run?  It was suggested
 > to
 > me to try a 3 blade 10x6 prop instead of my 2 blade 12x7.  I'm told I'll
 > get
 > the RPMs up increasing my horsepower, and bogging the engine less, which
 > will make the engine run cleaner, and won't make the plugs get oily dirty
 > deposits.  I'm wondering if I repitch my 12x7 to 12x6, would that work as
 > well, but still keep the boat sailing faster for potential racing.  For
 > now,
 > the 12x7 works just fine... I'm just thinking the engine might last me a
 > while longer if it's not working too hard all the time.
 >
 >
 > -Brian
 > L'Esprit #288
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