Lark IV 1962 40 hp, cooling? & help pls

K

kodibass

Master Chief Petty Officer
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Apr 10, 2010
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864
3 times a charm? I dropped L/U replaced impeller & it pumps water but only if I rev her up about 1/2 throttle. I dropped L/U a second time to make sure tubes were in place & they were. Removed t-stat same thing, removed pressure switch/ball same thing. I did not replace the aluminum pump housing or plate as they are pricy and mine looked fine. So I plan on dropping L/U again for a look, I am not that familiar with this model, but the manual I have (johnson 10th edition) has a jonny version & explains about water being re-directed back to the pump etc. So any ideas -help much appreciated. Pls feel free to be very direct, you are dealing with a simpleton :)
 
HighTrim

HighTrim

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Jun 21, 2007
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10,486
Re: Lark IV 1962 40 hp, cooling? & help pls

How cold is the water. They dont pump a ton until the t stat opens.

Cant hurt to run compressed air up the water line while the lu is down to ensure the cooling circuit is not clogged. I remove the t stat and flush back and forth on that model.

Other issues could be a clogged intake, or worn plate/housing like you mentioned.

Dont run that motor without the tstat and its assembly either or you will get hot gas pumped back down to the pump rendering it useless. THey make a better water pump than an air pump.
 
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stjon

Seaman
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Oct 14, 2012
Messages
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Re: Lark IV 1962 40 hp, cooling? & help pls

This is the first ever post I've made that is offering advice! As a complete newbie 6 months ago I've think I've made every mistake in the book - my motor sometimes did what yours is doing and I tried everything suggested EXCEPT I didn't sink the motor deep enough. The pee was intermittent assumedly because the water only rose to the needed height when there was turbulence created by my revving it. Try sinking the motor a little deeper - you never know...
 
K

kodibass

Master Chief Petty Officer
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Apr 10, 2010
Messages
864
Re: Lark IV 1962 40 hp, cooling? & help pls

Thanks I will do all above, was wondering also why do these motors recirculate warmed water back to the water pump?
 
HighTrim

HighTrim

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10,486
Re: Lark IV 1962 40 hp, cooling? & help pls

I would imagine to help it get up to operating temp in colder water. Without doing that, the t stat may never open. The whole system works well together, so a portion of it cannot be removed. Ensure that your t stat assembly is in good condition.
 
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