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1972 Johnson 25 - Flooding with suspected high-speed nozzle as the cause

fdrgator said:
One last theory--when you inspected the orifice plug, did you check the actual orifice diameter? A #72 plug should be 0.072" diameter hole. Lots of misguided folks will drill it out in the theory that more gas will make it go faster.
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(Completely revising my previous statement--it was boneheadedly incorrect)

I don't have a wire gauge larger than .03. But I was able to fit a 5/64 drill bit shank through the orifice. That's just a shade over .078. And that was also a loose fit, with considerable slop.

So voila! There's the ruptured dam. That was a great suggestion! To think I was only 1 step away from tossing the whole carb into the trash can...that advice saved it. Thank you!
 
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Good job, Gator.....you da man! Hope it works, Tony. Besides that, maybe you only have the 18 or 20? Did you confirm the powerhead? The 67 jet would be required, (see post #5), unless you have the 25 hp. Gator knew the nozzle was knackered.....he smelled the rat, eh? Let me know if you can't find the jet. Don't put the #72 in an 18 or 20 horse.
 
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timguy said:
Good job, Gator.....you da man! Hope it works, Tony. Besides that, maybe you only have the 18 or 20? Did you confirm the powerhead? The 67 jet would be required, unless you have the 25. Gator knew the nozzle was knackered.....he smelled the rat, eh?
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Haha! Nothing like a rat that smells like gasoline. See, I never thought to question it. I didn't know that the orifice designation was the actual size x 1,000, so that call-out was an especially timely one.

I've still not yet confirmed the powerhead. Though I have gained more confidence in it being a 25. Something about that orifice seems to support that. It clearly has "72" etched into the outside wall, which is specified only by the diagrams for the 25. I think if someone were to resort to drilling it, they probably also would not replace it--seems like a mutually exclusive thought process.

But even if it's not a 25 and actually does require the 67 orifice, I see it as: I have a bad 72 orifice. Replace that first; and if things still don't pan out and I end up downsizing, then at least I have a good 72 on standby for a future project.
 
I must say I have been glued to this thread,I can't wait to hear of a satisfactory outcome.Incidentally I have come across this problem
with the low speed needle several times myself,and now solve it with a dab of J B weld witch seems to do the trick.I cannot understand why they did not just thread the collar and needle in the first place but ,oh well,OMC have done a few things that I didn't understand.Any way I look forward to a good conclusion,be sure and tell us.
 
At last! Mother Nature had other plans for me this past week. Consequently, the new orifice arrived 5 days late. Comparing the 2 confirmed that the old orifice had in fact been enlarged. After replacing with the new one, I'm thrilled to report that the motor runs absolutely fantastic! Not yet tested on the water under load; but in the barrel, it's now batting high 9s. I couldn't be happier with the performance.

fdrgator is da MAN! Many thanks for that tip.
 
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