1973 Johnson 6 without full power...

[Tomm3]

My colleague has two 1973 Johnsons, one short and one long model. <br />Short one, although looking like new is not developing full power. Compresion on this engine much better than the on the long one, transplanting fuel pump, carburetor and electrical parts did not give results.<br />At local Johnson/Rude mechanic shop they said that possibly cilinders are "oval"?<br />And of course, he needs both of them, long for his big boat and short for dinghy.<br />Any idea what to do next?<br /><br />Thank you,<br /><br />Tom

 

[Paul Moir]

Re: 1973 Johnson 6 without full power...

Sounds like a long shot. If a cylinder was worn out of round, it would likely have turned up on the compression check. Another long shot would be a restricted exhaust on the short shaft, but I'm really just guessing here.<br />So you swapped the entire armature plate with the points & coils from the good running one to the bad? Did you leave the kill switch (if present?) disconnected when you tried that? Try pulling the spark plugs from the bad running engine and examining their firing ends. That might give a clue as to where the problem is. Or at least tell you if it's common to one cylinder.

 

[BF]

Re: 1973 Johnson 6 without full power...

It's deja vu, all over again. <br /><br />I'm having the same problem. See my thread from a few days ago. It lists what I 've done. Nothing has made the slightest difference. For lack of something else, I'm suspecting fuel pump (?).<br /><br /> http://forums.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=28;t=041374 <br /><br />I haven't been back out to the lake, so I have not progress to report.

 

[Tomm3]

Re: 1973 Johnson 6 without full power...

Update:<br />Motor was taken local Johnson mechanic, and they were puzzled with motor that looks like new, starts great, measured compression OK, got good spark on both cylinders, good fuel system but lacks power.<br />They offered to take dismantle it for free and to search for reason.<br />Result: Cracked rings on one cylinder.<br />Why the compression was so good?<br />No one knows.<br /><br />Best Regards,<br /><br />Tom

 

[BF]

Re: 1973 Johnson 6 without full power...

Hmmm... thanks for posting the update....<br /><br />I wonder if he ever tried running it with one plug wire off? I wonder if the cylinder with the bad rings was not doing much? (running on 1) ?<br /><br />Do you know what the result was? Need to bore it out (scored cylinder)? or just new rings?<br /><br />Just curious, because of mine....<br /><br />Thanks...

 

[Little_G]

Re: 1973 Johnson 6 without full power...

Oh boy, Not good to hear. I just got a 6hp johnson. I tryed it out on the lake today and it ran fine for about 30 minute's and hen went to spitting. Hope that's not a ring. I need a fuel pump I think but can't find on under 80 buck's. Anyone know of one that will fit?

 

[crxess]

Re: 1973 Johnson 6 without full power...

Rare to bust a ring on a 6 hp.
Most problems relate to Dirty carb - worn fuel pump - Spark issue from lack of ignition service. - head gasket from over heat(stuck thermostat or impeller failure)

All of which can be avoided by properly maintaining the motor.

When humans get lazy their machines fail to function properly.