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1 of 4 spark plugs is sandy color bone dry on v4 110hp Johnson

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supermansteve

New member
I have a 1987 Johnson OMC V4 110hp rough vibration, will do about 2 knots at full throttle. sunday on the water one spark (bottom right) plug is bone dry with tight tan color (may not be getting fuel) the other three are wet (getting fuel) got it home and found all 4 have a good blue spark, compression is about 115 across the board. I used a large sponge wrapped in plastic then cloth, with the engine running, I chocked out the top carburetor and the engine almost died down instantly. I did the same on the BOTTOM and it barley did anything, almost nothing. I rebuilt the carbs about 3 mos ago and I use Sea Foam. Any Ideas?
 
Will good " blue " spark jump a gap of 7/16" on all 4 cylinders ??----------Orange / blue stripe wire from power pack on both top coils. Plug wires to the correct cylinders ??--------------Reed valves checked ??---------------Did you remoove high speed jet ( 5/8" long ) from bottom of float bowls for cleaning.
 
Yes raceone, 7/16" blue on all orange blue is correct orientation, plug wires to correct locating, I already stated I rebuild the carbs. Boat ran fine two weekends ago. Reed valves looked ok the last time I had the carbs off. The reed's was my suspension due to the fact there was not much suction to the bottom carb. no suction no fuel, I know but why am I getting fuel to left bottom and not the right?
 
supermansteve said:
I already stated I rebuild the carbs.Why am I getting fuel to left bottom and not the right?
Click to expand...

Yes, you already stated that you rebuilt the carburetors BUT that doesn't answer Racerone's question of "Did you remove high speed jet ( 5/8" long ) from bottom of float bowls for cleaning." Regardless... clean the high speed jets manually with a piece of single strand steel wire as cleaning solvent just doesn't do that job properly.

If the engine ran normally since you rebuild those carburetors, the problem sounds like debris of some kind has either blocked off the float needle valve(s) OR clogged the high speed jet(s). Either scenario would prevent fuel from gaining access to the related cylinder.
 
Thank you joereeves, when I stated I rebuilt the carbs, I ment I REBUILT THE CARBS, meaning everything. I didn't want to bore everyone with every detail. I did a chem dep, I used copper stranded wire not steel, I took all jets out. Used a new rebuild kit. I agree it seems like there is some kinda blockage. Do you think a blocked reed valve could cause one side to get fuel and not the other? Keep in mind when I blocked off air flow when the engine was running not much happened meaning the engine didn't suck more fuel and not air causing flooding, "chocking" The top carb really grabbed ahold, lots of intake power not the bottom.
 
The question about the 5/8" long orifice has still not been answered clearly.--------I wish I could put on my " blue caped suit " and fly over to help you.-------------You must answer questions to get further help.-------------Perhaps the lower crank seal is blown ( quite rare ) and that would mean little suction on one carburetor throat.
 
The question about the 5/8" orifice still not been answered? Can you clarify what you mean by that? How do you check the lower crank seal? Would the reed plats have any impact on suction on one side of the carb?
 
Did you remove the high speed jet ( orifice ) from the bottom of the carburetor bowl.-It is about 5/8" long.--------Each carburetor bore feeds one cylinder and one cylinder only.
 
racerone said:
Did you remove the high speed jet ( orifice ) from the bottom of the carburetor bowl.-It is about 5/8" long.--------Each carburetor bore feeds one cylinder and one cylinder only.
Click to expand...
YES,YES,YES I said before, I removed them and cleaned them with a copper wire. I know how to rebuild a carb. Have been doing them for 20 some years now.
 
Steve.... The reed plate (leaf valves) consist of many finger type flapper leaves so if one was blocked shut, I doubt if it would be noticable. On the other hand, if any of those leafs were jammed open via any foreign article, that would interfere with the vaccum needed to drawn the fuel in.... this type problem would show itself in the form of fuel being blow out the carburetor throat on every down stroke of the related piston.

There are four high speed jets, two to a carburetor, one obviously for each cylinder. I am assuming that you have removed all four (4) and cleaned them manually with the copper wire that you've mentioned. If you haven't cleaned all four, do so... if you have, there's always the possibility that some debris has broken off with a fuel line (whatever) and is interfering with a jet.

Do the two finger test. With the engine acting up, stick two fingers in the carburetor throats, one carburetor throat at a time of course (not the complete carburetor at the same time), and note the response. A drop in rpm indicates you've caused a increase in the fuel quanity which is flooding the cylinder BUT if the test causes a cylinder to increase the rpm and smooth out... you've found an offending carburetor.

The problem to me (without actually being there) spells carburetor. You asked in your second post (actual #3 above) "why am I getting fuel to left bottom and not the right?"

Many boaters have the habit of (for the winter) having their engines tilted up and swung to one side. That results in two of the high speed jets being higher than the other two with the result being that two jets are most prone to fouling. Which in turn results in one bank of the engine running lousy if it fires at all. This is of course assuming that the compression and spark is as it should be.

You indicate that the rig is doing about 2 mph at full throttle. Has this improved? This would have to be more than one cylinder failing. The compression you state of 115 psi on all cylinders is great, and you've indicated that with the spark plugs removed that the spark does jump a 7/16" gap. These two areas, in that condition, would be perfect. Too bad you're not close by.
 
joereeves said:
Steve.... The reed plate (leaf valves) consist of many finger type flapper leaves so if one was blocked shut, I doubt if it would be noticable. On the other hand, if any of those leafs were jammed open via any foreign article, that would interfere with the vaccum needed to drawn the fuel in.... this type problem would show itself in the form of fuel being blow out the carburetor throat on every down stroke of the related piston.

There are four high speed jets, two to a carburetor, one obviously for each cylinder. I am assuming that you have removed all four (4) and cleaned them manually with the copper wire that you've mentioned. If you haven't cleaned all four, do so... if you have, there's always the possibility that some debris has broken off with a fuel line (whatever) and is interfering with a jet.

Do the two finger test. With the engine acting up, stick two fingers in the carburetor throats, one carburetor throat at a time of course (not the complete carburetor at the same time), and note the response. A drop in rpm indicates you've caused a increase in the fuel quanity which is flooding the cylinder BUT if the test causes a cylinder to increase the rpm and smooth out... you've found an offending carburetor.

The problem to me (without actually being there) spells carburetor. You asked in your second post (actual #3 above) "why am I getting fuel to left bottom and not the right?"

Many boaters have the habit of (for the winter) having their engines tilted up and swung to one side. That results in two of the high speed jets being higher than the other two with the result being that two jets are most prone to fouling. Which in turn results in one bank of the engine running lousy if it fires at all. This is of course assuming that the compression and spark is as it should be.

You indicate that the rig is doing about 2 mph at full throttle. Has this improved? This would have to be more than one cylinder failing. The compression you state of 115 psi on all cylinders is great, and you've indicated that with the spark plugs removed that the spark does jump a 7/16" gap. These two areas, in that condition, would be perfect. Too bad you're not close by.
Click to expand...

joereeves
Do you think there might be a possibility of a vacuum leak? I plan on taking the carbs off again one day this week, maybe Thursday. But would like to check for a air leak if there's a way you know how?
 
Put boat into the lake.----Have an assistant drive the boat with full throttle.-----------Now shine a strong flashlight into the carburetor bores .----Observe and compare amount of fuel coming up the main jets on all 4 throats.------------Each throat feeds one cylinder.
 
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