Johnson 6hp Model GR-72D. What year?

T

tomclark

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Sep 17, 2001
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I need help getting some information on this motor.<br /><br />Model: GR-72D<br />S/N: J3553120<br /><br />What year/years of manufacture?<br />What Ratio of gas to oil?<br />Spark Plug gap (Champion J6C)?<br /><br />Motor has long shaft and is used on a sail boat. Runs real good and I want to keep it that way!<br /><br />Thanks
 
JB

JB

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Re: Johnson 6hp Model GR-72D. What year?

Sorry, Tom. My charts only run up to 1964 and the GR is not in there.<br /><br />The good news is that your engine is almost cetainly new enough to use a 50:1 mix. Try it with caution. Any sign of overheating and you go to 32:1. (1.5 pints/6 gallons)<br /><br />I would try a J6J Champion and see how well it does high rpm runs. If that works, try a J4J. If the J4J doesn't foul at idle speeds stick with it. It is a cooler plug and should work better at WOT.<br /><br />Red sky at night. . .<br />JB :)
 
F

fone_man

Senior Chief Petty Officer
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Jul 8, 2001
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Re: Johnson 6hp Model GR-72D. What year?

I would say you got Model # wrong/typo???<br /><br />GR-72D is probably a...<br /><br />6R-72D which is a 1972 Johnson 6 HP!!!<br /><br />As small as ome numbers/letters are... easy to do!!!!<br /><br /> :D
 
T

tomclark

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Re: Johnson 6hp Model GR-72D. What year?

Thanks for all the replys. 1972 sounds about right for the year, I'll check for the "6" when I'm at the boat tomorrow. <br /><br />As far as switching to a coolier plug I think I'll stick with the J6C. Most of my operation is at very slow speeds just above an idle so my guess is the hotter plug would be best. Is that correct?<br /><br />Also, does anyone know what the gap setting should be or will it be OK out of the box? <br /><br />Thaks
 
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