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Johnson 60 1995 boogs down on throtle

M

marek1981

New member
Hi there everyone!

I'm new here on this forum pretty much but have been reading a lot and got many good information thanks to all good and knowledgeable peoples here.

I can't say that I'm beginner in outboards, had many johnrudes thru years, few rebuilds from 9.9, 20, 25 and recent nice 4hp evinrude that I'm still using on my dinghy.

Now here I came across with johnson 60 hp that has given me lots of headache. Here is story and what I have checked/done so far.

Carbs taken off, cleaned thoroughly in good shape float set to spec.
All fuel lines checked, prime bulb is hard no fuel leak.
Fresh fuel mix
Compression 135 PSI on all 3 cyl.
Spark test good, coils and wires in specification
TDC checked with piston stop tool-OK
VRO deleted - old fashion fuel pump instaled-fuel pressure at 2500 rpm is constant 3-4 psi
By disconnecting ignition cable from plugs I have notice that top cylinder runs much stronger than lower two, looks like lower two cyl doesn't run full power at all.
Link and sync set by spec.

What is happening is when uder load in gear and advancing with throttle engine bogs and dies all the time, I can rev it up in neutral but with any load it stalls and dies if not put back in neutral.
I can't make it idle with carb butterflies fully closed, have to leave them open slightly and have to advance idle timing to make it idle.

When turning flywheel by hand I can hear and feel top cylinder sucking air but lower two much less or nothing.

I'm suspecting that motor is not achieving good crankcase vaccum on lower two cylinders and that is the reason why it's not sucking enough fuel from carbs and bogs down on throttle running only on one top cylinder and that might be a reason why I cant set normal idle with carb butterflies closed and need to advance idle timing to 2-3 deg. BTDC instead of 4 deg. ATDC by specification to make it run.
Also I did spray carb cleaner around crankcase seam and notice slight change in rpm.

My next plan is to take flywheel of and visually check key and other ignition components.
And then pull off powerhead and try to do a leak test on crankcase and reseal if necessary.

What do you guys think I'm I going right direction?

This engine is making me crazy.

Any suggestion or idea would be much appreciated!!!!

Thanks,

Mario
 
Crankcase vacuum does not play any part in getting fuel to the cylinders. That is accomplished by the pistons downward travel "Crankcase Pressure" forcing the fuel mixture out of the crankcase area and up to the intake port area.

The problem you describe is most normally due to a servicing personnel when cleaning/rebuilding a carburetor(s), overlooking the hidden high speed jet that is located in horizontally in the bottom center portion of the float chamber. Solvent and pressurized air just doesn't do that job properly... clean all of them carefully with a piece of single strand wire.

The high speed jets are removable (1/4x20 threads) but use great care with the screwdriver. Below is what the removing/installing tool looks like (click to enlarge)... easy to make, just takes time. The shank should just clear the 1/4x20 threads of the drain screw. Ignore the pricing, it's long gone.
317002_CARB-JET_REM-INST.JPG
 
Taking the powerhead off to evaluate crankcase leaks may well be the wrong approach.----I believe spraying carb cleaner on the seam is also a flawed test.-----Just my opinion.----Cylinder sleeves still in the right position ?
 
Thanks Joe for quick reply!!

But doesn't piston when traveling towards TDC produces some kind of vacuum on crankcase side and suck air in thru carb ventury and pulls fuel out and mix with air after that when piston is going back it produces pressure forcing mixture into combustion chamber pushing exhaust gases out thru exhaust ports?

I did check and unscrew btm holding nut and clean them thoroughly, I have "special" homemade screwdriver for that :)
 
racerone said:
Taking the powerhead off to evaluate crankcase leaks may well be the wrong approach.----I believe spraying carb cleaner on the seam is also a flawed test.-----Just my opinion.----Cylinder sleeves still in the right position ?
Click to expand...

Thanks for response racerone!
To check cyl sleeves I would have to pull head off or open crankcase I haven't done that yet.
 
Do you guys think that problem might be crankshaft seals, lower or ones between cylinders?
Top one is good I have checked that.
And I have checked reeds are in perfect condition.
 
What Joe is saying is that once the fuel mix is in the crankcase, then it is pressurized on downward travel of the piston and shoots into the cylinder. The initial charge from the carb/carbs is initiated by vacuum as the piston moves upwards. We all likely understand this, but I am defending Mr. Reeves explanation, as well as addressing your statement.
To answer your question on the crankshaft seals, you may be on to something but it is uncommon to find. Ethanol may be to blame for injuring these seals, if this is the case. I assume its had a regular diet of ethanol at one time because the VRO has failed and been replaced.:(
 
Yeah, VRO delete was before my era with this motor but I agree timguy Ethanol and eventual overheat due to VRO fail might be scenario that had happened.

I think I'll have to scratch more under skin here.
There are not many things left to do before pulling powerhead off.

Could head gasket have good compression but still be bad on inside and letting air escape?
Because lower two cyliders are equally bad that could mean bad crankshaft seal between them, if only bottom seal is bad that would effect only btm. cylinder?
Does this make sense?
 
Head gasket? No, in my opinion. Racer is right. I have thought of making a gauge to measure vacuum at the carb throat. Still haven't done it. With multiple carbs it would be a great tool for diagnostics.
 
Just an update from yesterday. When I was taking off spark plug I have notice small drops of water on lower two spark plugs and they were all three covered with white yellowish milky substance. Now Where is that taking me? Head gasket if I'm lucky enough?
 
New game. Head gasket could be the culprit, gotta remove carefully and inspect, but such good compression?
 
Yes that confuses me, so good compression! Now I'm wondering if water could get into crankcase somehow and then into cylinders thru intake ports. Or could be head gasket bad at special spots. However head is going off today and hopefully that will give some more answers.

I just want to thank you guys for helping me out here !!
 
Any report yet? It would be unlikely that water could be introduced in any way to the cylinders other than a head gasket, unless it is in the fuel. I have occasionally got fuel from the gas station that is contaminated. Never gas up while the station's fuel tanks are being refilled. If I see that, I go to another station.
 
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Yes I menage to take head off after 4 snapped bolt heads of total 14. It was PITA. But gasket on cylinder side of water jacket was not cracked that explain good compression but on outside and above water jacket was total toasted and needed changing.
Bottom two cylinders had trace of rust above TDC line.
Head surface is bad, I can't get it out with sand paper so I'll have to facemill it.

Now when I rotate flywheel I can still hear top cylinder suck and push air and btm. two just little.
Can crankshaft seal between btm. and middle cylinder be that bad?
If I get it right split sleeve play roll of sealing? How can they fail actually?

I'm afraid that only changing head gasket won't solve problem so I might just pull whole powerhead off and split crankcase.
 
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