96' Johnson 30hp- I just cant get this motor to run right

KB976

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Im on the same page as you and jakedawg, I think the bowl is running out of fuel. I wil try this test tonight as I have not done this yet.

Along the same lines, can I test flow by pulling that same line and not plugging it? I would think I should see a pressure change on the output of fuel as I ramp up the rpm's. is my theory right here?




So I did this test, plugging the line to the fuel primer and capping the intake on the primmer, no change from before. I also ran the boat with the line to the primmer un-restricted and was able to see a very apparent flow difference as the RPM went up. This leads me to believe the fuel pump is working properly.
 
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KB976

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I do have an air gap tester. What do you mean by fully advanced? what RPM rang do you consider fast idle?

I ran this test as described with the gap at 7/16 measured with a micrometer. nice spark line jumping from end to end on bother cylinders.
 

jakedaawg

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So, you are saying that the fuel inlet is on the Bottom? That is the ay older carbs were. I wonder if someone han't replaced the carb at some point. This would lead to the wrong carb kit and posible our issues
 

jakedaawg

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Please post an actual pic of carb. Also compare model # on engine clamp to the model # on the matal disc on the top of the cylinder head.
 

KB976

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So, you are saying that the fuel inlet is on the Bottom? That is the ay older carbs were. I wonder if someone han't replaced the carb at some point. This would lead to the wrong carb kit and posible our issues


Yes, the fuel inlet is on the bottom of the bowl, just as you had described in one of your earlier post.

Do these pics help at all?



 

KB976

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numbers on the cylinder head plate right under the bottom sparkplug hole are D2 327673

what clamp are you reffering to
 
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oldboat1

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#18 is the low speed needle. #19 is the high speed orifice. The h.s. orifice is suspect. As it's idling OK, recommend taking the bolt out and running a wire through the orifice after the fuel in the bowl drains out. I see a little fuel around the bolt, btw, which might indicate that it is leaking a bit. Look for a partial blockage in the h.s. jet (should be able to try to clear the jet w/o removing the carb again).
 

KB976

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#18 is the low speed needle. #19 is the high speed orifice. The h.s. orifice is suspect. As it's idling OK, recommend taking the bolt out and running a wire through the orifice after the fuel in the bowl drains out. I see a little fuel around the bolt, btw, which might indicate that it is leaking a bit. Look for a partial blockage in the h.s. jet (should be able to try to clear the jet w/o removing the carb again).



How does that high speed orifice work? that is behind the bolt which drains the bowl, not sure how it can work at all?
 

KB976

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another thought... could it be timing? would this be the symptoms if the timing was not advancing with the fuel and air increase? I dont think its the case, but as stated by jakedawg im trying to go back to some of the basics. How can i test the timing on this?
 

oldboat1

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If you haven't cleared that h.s. jet, would say that is likely the cause of the symptom. Would sure explore that.
 

oldboat1

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...and with function in mind, spray carb cleaner through the jet (goes up into the carb). jet feeds from the bowl. Spray is a combination of solvent and air pressure -- don't flood the carb with solvent; just clear the jet.
 

KB976

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#18 is the low speed needle. #19 is the high speed orifice. The h.s. orifice is suspect. As it's idling OK, recommend taking the bolt out and running a wire through the orifice after the fuel in the bowl drains out. I see a little fuel around the bolt, btw, which might indicate that it is leaking a bit. Look for a partial blockage in the h.s. jet (should be able to try to clear the jet w/o removing the carb again).

So I pulled of the bowl plug and all the fuel ran out. I then ran a pipe cleaner in it. Still curious as to how that works. Can it be adjusted like the low speed needle can? Wouldnt the fact that the fuel came out indicate through the orific indicate it wasnt plugged in the first place?
 

oldboat1

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nope. fixed jet. (I like the old adjustable ones, but no matter.) Fuel should go up through the center of the bowl, controlled (amt) by the jet. Recommend a fine wire rather than a pipe cleaner -- like cleaning your ears: Don't shove the stuff further in.... [keep face away, but check in the carb throat when spraying -- believe you should see the solvent come up there. does when sprayed from the top, anyway, when cleaning the idle speed openings]
 
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KB976

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nope. fixed jet. (I like the old adjustable ones, but no matter.) Fuel should go up through the center of the bowl, controlled (amt) by the jet. Recommend a fine wire rather than a pipe cleaner -- like cleaning your ears: Don't shove the stuff further in.... [keep face away, but check in the carb throat when spraying -- believe you should see the solvent come up there. does when sprayed from the top, anyway, when cleaning the idle speed openings]


Ok, pulled it again, ran a micro wire in the orifice, then took some carb cleaner and sprayed it in the orfiice and it shot up and out in the carb throat coming out of the hole the main jet goes down in.
 

oldboat1

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OK. That sounds promising, if I follow. Cross fingers and fire it up.
 

jakedaawg

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Sorry Kb, I was under the assumption that you had had that jet out and cleaned it when you rebuilt the carb. That is, from appearance, the proper carb for that year.
 

jakedaawg

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You can actually remove that jet with a small screw driver. If you dont have one that fits take one and grind it so that the blade and shaft are true and fair, it will then fit in where the bowl drain is and allow you to remove the jet. This is done with the bowl off. Then you clean the passages that go to the jet with carb cleaner and air nozzle. It is best never to run a wire or pipe cleaner through a jet. I know the old timeers did it for years...just sayin'. These are machined parts made of soft brass or silca bronze or whatever and a steel wire is harder and can damage the orifice.
 

KB976

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So it fires up and idles great as always, get the rpm's up and it still acts like its starving for fuel wanting to dog down and die. I can back it off and prevent it from dying which is a good sign as that is an improvement because, before once it started its rpm decline I typically couldn't stop it and just had to let it die so i can start it again.

next test is to see what it does in the lake, see if the decline is still preventable once it starts.
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