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1988 90 Hp Johson just not getting enough fuel- Model J90TLCCA

johnnyv4449

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so I done a number of tweaks on this engine. New coils, plugs wires carbs rebuilt, fuel lines, fuel pump, filter, primer ball and fuel tank but I just am not getting enough fuel to the carbs. I changed it to premix and replaced the pump with a regular pulse pump. I've adjusted the linkages (I think correctly) and the butterflies are straight open at WOT. The engine runs fine but I can tell there is missing power. If I hit the choke button on the kit it revs up perfectly so Im sure that it is not getting enough fuel.

what adjustments can I make on these carbs to get this fuel into the engine. There are no jet adjustments on these carbs.

Any ideas?
 
Next you should revisit the main jets and clean them out carefully with something very strong like CRC Throttle Body Cleaner and then use a set of welding tip cleaners which are soft enough that they won't harm the jet. You need to synchronize carbs when the butterflies are closed. You must note carefully that they all begin opening movement at the same precise moment. One cannot get the required accuracy by looking to see if they are all flat, or perfectly parallel with the carb throat.
 

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I have a 1990 90 hp. You definitely need to be sure your jets are perfectly clean as TimGuy states. And compression is always the first test. Since hitting the key makes it improve it is probably something to do with carbs. If your jets show clean, then you may be getting an air leak somewhere. If you have the plastic carb bowls, that could be a good place to check, as they will subtly warp and allow air in. This won't show up as a fuel leak. Take off your bowls and lay some sand paper down on a piece of glass, then sand your bowls on that in a figure eight pattern. That will show you if they are perfectly flat. After I got mine where it was sanding everywhere on the bowls, it totally fixed my issue at high speed. Let us know what you find.
 
So I checked the compression on all 4 cylinders and each is within 1 or 2 lbs of 95PSI. I gapped the plugs to .30 as per the manual and adjusted butterflies, cables and and linkages so that I get the carbs fully open. I was not able to set the marker on the linkages because every time I set the mark to the middle of the linkage roller, the cable would not pull the engine all the way back to idle. what pulls that timing arm back fully? So essentially they are probably all off.


It essentially is running terrible now. I'm not sure how to align all of these settings. How is this engine timed? There is a significant miss in th etiming enough to shut it down at idle. I have the manual but it does not really make sense.
 
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Some will argue.----If your compression test numbers are accurate you perhaps need to take one cylinder head off for inspection of cylinders.-----Compression is way to low.------Mere pennies for a new head gasket so to speak.
 
You state what you think is the problem... BUT... you do not state exactly what the engine is doing or not doing. Normally a case of the engine pretty much idles and runs slowly fairly decent, but as the throttle is advanced, the engine wants to die out.

At any rate, I'd suspect that the four brass high speed jets are restricted.

The fact that engaging the "Fuel Primer Solenoid" (There is no choke on that engine) causes a increase in power indicates clogged, gummed HS jets that are located, each one, in back of the carburetor drain screws, near the bottom center area of the float chambers. Make sure that all four are perfectly clean.
 
So I checked the compression on all 4 cylinders and each is within 1 or 2 lbs of 95PSI. I gapped the plugs to .30 as per the manual and adjusted butterflies, cables and and linkages so that I get the carbs fully open. I was not able to set the marker on the linkages because every time I set the mark to the middle of the linkage roller, the cable would not pull the engine all the way back to idle. what pulls that timing arm back fully? So essentially they are probably all off.


It essentially is running terrible now. I'm not sure how to align all of these settings. How is this engine timed? There is a significant miss in th etiming enough to shut it down at idle. I have the manual but it does not really make sense.


So first I wanted to thank everyone on this forum for all of the help!

I took the carbs apart and cleaned them. I sanded the bowls as was suggested by riopga and they were not flat. I gapped the plugs to .40 as well. Then I started from the bottom up on the linkages, and cable settings. I dropped it in for a test ride and aside from a few small cable and idle adjustments it ran FANTASTIC! Thanks again to all of the knowledge this forum provides!
 
Yes these guys are good here. If our customers do as they are guided, the problems can either be resolved, or at least defined accurately. Then the boat owner will decide from there what to do....replace it, or repair it. Our top dogs here have well over 40 years of hands on work. Some are still very sharp at over 80 years old devoting hours each day to help strangers.....for free.
 
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