[Public-list] Atomic 4 compression

[J Bergquist]

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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