Conference unifix::sailing

>We just can't figure out why the new impeller works initially, then dies.  I've
>attributed it to the cold/warm engine scenario, but we really want to find 
>out, 'cause impellers cost $20 a pop.  

Impellers frequently die when they are run dry.

Perhaps, when your engine is started warm, i.e. the thermostat is open,
there is no water in the water pump? Or possibly the pump sucks a big air bubble
which has accumulated in a high spot in a hose?

I don't know anything about the cooling system on an Atomic 4,
so I can't help with the details.

--RS

    
    I don't think Atomic 4's like to be shut off hot.  Ours has an external
    thermostat in a T connector that recirculates the water utill it
    is up to temp, then sends it out the exhaust.  Whenever we shut
    it down hot, the thermostat sticks and when we restart it, it runs
    rough.  The boat came from Florida where it never had a thermostat,
    just pumped water all the time.
    
    Phil

    The atomic 4's can be shut off hot or cold.  The most likely problem
    is air or blocked flow.  Start at the salt water intake, make sure it
    is not blocked (or the screen so painted over it is "starving" the 
    water flow, check all hose clamps and the hose to ensure the pump is
    not sucking in air, the impeller cover seal for leaks.  Rubber impeller
    parts would not be a problem unless your system re-circulates.
    Then add an extension hose from the pump output into a bucket and
    determine that you are getting a good flow. (Just run it briefly, or
    you would over-heat your engine...Do it when the engine is cool.  Does
    your atomic 4 have a thermostat? (Some do not) Is it possible there 
    is air in the system?  Incidently, I have not had to replace an
    impeller since the engine was new in 1979 (however, I am re-circulating
    anti-freeze plus lubricant, since I installed fresh water cooling.)
    

    The impeller needs to be put in with the lobes bent in the correct
    direction, trailing as the shaft rotates.  If you put it in backwards,
    it'll fail virtually immediately.

    A suggestion on impellers, if its an Oberdorfer pump.   Use Monahan
    Pump Supply in Norwood, 617 762-2343, better prices.    (if its a
    Sherwood pump, you might want to get an Oberdorfer, it has more
    capacity.)
    
    I've had an Atomic 4 for a number of years, sounds like an air block or
    air leak/blockage in the system ie: the seastrainer, secock,hose to
    pump inlet.      Check it over.      Also check your by pass hose if so 
    fitted.  (T fitting for Thermostat, when it is closed ie: a cold engine
    water is diverted back to the pump via the by pass valve and hose, in
    non- thermosat engine it allows you to regulate the water temp ie: if
    raw water cooling temp is too cold bleed in more hot water off the by
    pass.)

We have a fresh-water cooled by sea-water system that we flushed out after we 
put on a new pump head.  Something about a burr missing or something.
There WERE pieces of rubber clogging the hoses, and the impeller was burning up 
because there wasn't enough water to keep it cool.  

We still had a mishap coming through the mouth (of the Merrimack) again, though,
because we forgot to tighten a screw on a hose and it blew off.  We haven't
checked the impeller because we stopped to engine, filled up the water, and
the amount of water blowing through appears to be fine.  

See what happens....

Thanks!

We are STILL getting towed in from the mouth (of the Merrimack) after sailing.  
It's getting rather embarrassing.  Everytime we replace an impeller, run the 
engine on the way out, and then try to go back in, we get stuck.  The pump 
refuses to pump water because the impeller's gotten chewed up.    

Now we're thinking of replacing the pump (we wish we could replace everything!).

VERY UPSETTING!  

HELP!

Thanks.

Ann

    Ciao Ann: Does it get chewed up before or after the re-start? Could be
    you have an air leak above the waterline on the intake side and when
    hot the backpressure is too much to overcome and no water is sucked
    into the system. I have a friend, Kevin Crowley, with an old Friendship
    sloop moored off Windward Marina. He is excellent with these engines;
    give him a call over and with a beer he will fix it! Give him my
    regards! The name of the boat is Flying Jib; white with a L O N G
    bowsprit. Good luck, Ed

RE: .7,

>>>  Everytime we replace an impeller, run the engine on the way out, 
>>>  and then try to go back in, we get stuck.  

Go ahead and spend the money on a bi-directional impeller.  Apparently 
they've been selling you only an outbound model, when you obviously need 
a combination outbound-inbound one.

J.

;-)

My husband spent another day on the water pump and realized that the shaft was
not connecting properly with the impellor, which was causing it to run dry and 
get chewed everytime we turned the motor off and then on again.  We had noticed
that the impellor was not fitting in properly, but didn't realize that the shaft
was not slotted in correctly.  (Please excuse my nontechnical description.)

We've gone out the last couple of nights, but didn't turn the motor off the 
fist night.  The next night, we started the motor, and no problem with the 
water pump.  We went sailing and when we turned the motor back on--voila!--the 
water pump was still pumping water!  Gushing!  Hooray!  We checked the water
pump several times and it was nice and cool.  

Now it's time to fix the electrical system (that stopped charging).

Thanks.

Ann