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97 johnson still wont run!!!!!!!

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steelhorse1369

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After many hours I guess im stumped I have been around boats all my life have never found a motor i couldnt make run. This is a 97 Johnson 40 hp, only had it about a year dont know the history of the motor. its on a pontoon was running fine and lost power at full throttle went down to near idle ,it was immediately turned off and checked ,it was not overheated all looked good. When tried to restart it fired and died would not stay running.First thing you think fuel issue, it had a vro pump with the oil line cut and plugged with a bolt, didnt like that to start with so I started there, converted to a standard pulse pump mounted on on the block, pulse for the vro was properly plugged at the motor,fuel and vacuum lines all replaced, still same result so I still thought has to be fuel, noticed fuel dripping from front of the carbs, got carb kit and cleaned /rebuilt carbs reset floats set idle screws at 1.5 turns from soft seat,drained fuel supply line and fule lines on carb hooked up new tank of marine fuel,,, same result fires and dies.Replaced primer bulb and supply line and connections,same thing fires and dies ,pulled carbs back off checked my work and checked reed valves all ok, same thing, still has to be fuel delivery. Took carbs back off took to a friend that dose marine work he checked carbs, same thing, thinking now it could be electrical, checked spark, bolth plugs fireing consistently , checked to make sure pistions were top dead center with marks on fly wheel and are, compression check 130 top 115 bottom ,not great but should not effect the motor from running. Replaced plug wires and spark plugs,yep same sh--t, new coil,yep no change, IM stumped what am i missing, may be next replace power pack. I just dont get it i must be missing some stupid little thing . ANY IDEASAfter many hours I guess im stumped I have been around boats all my life have never found a motor i couldnt make run. This is a 97 Johnson 40 hp, only had it about a year dont know the history of the motor. its on a pontoon was running fine and lost power at full throttle went down to near idle ,it was immediately turned off and checked ,it was not overheated all looked good. When tried to restart it fired and died would not stay running.First thing you think fuel issue, it had a vro pump with the oil line cut and plugged with a bolt, didnt like that to start with so I started there, converted to a standard pulse pump mounted on on the block, pulse for the vro was properly plugged at the motor,fuel and vacuum lines all replaced, still same result so I still thought has to be fuel, noticed fuel dripping from front of the carbs, got carb kit and cleaned /rebuilt carbs reset floats set idle screws at 1.5 turns from soft seat,drained fuel supply line and fule lines on carb hooked up new tank of marine fuel,,, same result fires and dies.Replaced primer bulb and supply line and connections,same thing fires and dies ,pulled carbs back off checked my work and checked reed valves all ok, same thing, still has to be fuel delivery. Took carbs back off took to a friend that dose marine work he checked crabs, same thing, thinking it could be electrical, checked spark, bolth plugs fireing consistently , checked to make sure pistions were top dead center with marks on fly wheel and are, compression check 130 top 115 bottom ,not great but should not effect the motor from running. Replaced plug wires and spark plugs,yep same sh--t, new coil,yep no change, IM stumped what am i missing, may be next replace power pack. I just dont get it i must be missing some stupid little thing . ANY IDEAS
 
So it sounds like spark is good, comp is good, that leaves gas.
Couple of things you can try...
1. Spray premix into the carbs. It should fire, and run for as long as it can on that gas.
2. Turn primer solenoid manual valve to manual mode. Squeeze primer bulb twice. Turn manual valve to sorta mid point.
Try start. You can maybe get it running on just the fuel from the half open primer solenoid manual valve.

Both these tests will prove out if it is fuel related.

So, if it is, why is the fuel not being pulled from the carb? Ok, the top gasket could be leaking. The idle air bleed circuit may be clogged/stopped up.
The center donut gasket on the nozzle stem might be missing.
Hard to think you could do that on both carbs....but something to check.
 
I have checked and double checked If i spray fuel into the carbs it floods out plugs are wet when you pull them, you would have to think its fuel but I cant find it. When I pulled the carbs off one of the many times with them off I hit the key and it took off like a racehorse till it ran out of fuel , looked at the reeds they look fine ,going to try a new power pack dont think thats it but we"ll find out
 
Ok so it is flooding out. Floats right? Primer solenoid not leaking? Have you verified the initial setting of the needle is really 1.5 turns out? Maybe it should be more.
I don't have the book on that model.
 
Not flooding it starts and dies, plugs are ok , if you spray gas into carbs to try to keep it running it wont do anything and plugs come out wet.On carb settings I started out at 1.5 turns from soft seat an went in till it would do nothing came back out till it would start and die 1.25 turns went all the way out to 4 turns 1/4 turn at a time with same results. Thanks, Mark
 
I am thinking air leak.
air leak behind the carburetor---air leak from crank case maybe under powerhead or under flywheel. Do plugs come out wet only when you dump gas in carburetors but not when you attempt to start by using the * choke?
It did quit all of a sudden. very suspicious.

* I have been away from working on outboards for 45 years. I guess chokes are a thing from the past..
 
daselbee said:
Third line from bottom, he says he has verified TDC physical piston location with the pointer
Click to expand...

Needs to be checked along with making sure everything is tight under the flywheel. the motor has fuel ,compression and spark and doesn't run. Flywheel only tells you the the pistons are in time.
 
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flyingscott said:
Needs to be checked along with making sure everything is tight under the flywheel. the motor has fuel ,compression and spark and doesn't run. Flywheel only tells you the the pistons are in time.
Click to expand...

I don't understand what you are saying. Please explain. If the #1 piston is at TDC, and the flywheel TDC mark is on the pointer....the key is good. No?
 
daselbee said:
I don't understand what you are saying. Please explain. If the #1 piston is at TDC, and the flywheel TDC mark is on the pointer....the key is good. No?
Click to expand...

If the key is not completely sheared only bent you can end up with the timing marks on the flywheel and the pointer being close. Unless top dead center was found with a piston stop or dial indicator I would check it. There is also the question of everything being tight and correct under the flywheel. I think it's worth a check along with the crank seals.
 
The magnetic timing ring is epoxied onto the flywheel hub.
If this epoxy fails the magnet ring can conceivably spin some.
TDC would still agree with the TDC mark on the flywheel.
This would throw the timing off while still maintaining spark. The compression and gas would remain the same.
 
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^^^^Yes I understand THAT.....but we were discussing the key. If everything is as I posted...piston physically at TDC, mark on flywheel is at pointer...then KEY is good.

And that is what the OP posted originally, or that is the way I read it.
 
OP....does it produce suction at the carb venturis? Place hand over carbs and see if it is sucking when cranking.

It seems as if it is not pulling gas, for some reason.


Help me make sure I understand.....you spray gas in, it fires and dies immediately. But you remove the carbs, and any gas remaining in the crankcase makes it fire and run "wild" for much longer, until it dies out? That would say to me that the amount of gas in the engine (behind the carbs) is much greater than the available air, and that it is basically flooded and cannot run. Take carbs off, you have an unrestricted airflow and it burns off quickly....
 
daselbee said:
^^^^Yes I understand THAT.....but we were discussing the key. If everything is as I posted...piston physically at TDC, mark on flywheel is at pointer...then KEY is good.

And that is what the OP posted originally, or that is the way I read it.
Click to expand...

I am not going to hijack this thread about why I think the flywheel should be pulled and key checked I explained that. Good luck with your motor.
 
If I use the choke it floods , if I use high idle it starts spits and dies if you try to start it with high idle down it will run about 10 seconds sputtering and die , spray fuel in carbs it floods , hold the butterflies open manually it starts spits and sputters then dies. Take carbs off and and start it it will run uncontroled and smooth till fuel is gone. I still its a fuel situation must be somthing im missing
 
One post I viewed on another forum said reed valves I looked at them when I took carbs off but did not take the manifold off and check them , maybe that should be the next step
 
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