HELP GOING NUTS & JOHNSON STILL WONT RUN

[steelhorse1369]

97 johnson still wont run!!!!!!!
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 drained carbs 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, sprayed gas into carbs while trying to start flooded out would not fire pulled the plugs all wet, thinking now it could be electrical, checked spark, bolth plugs fireing consistently but not bright blue , 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 , next 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 . THIS IS DRIVING ME NUTS!!! ANY IDEAS THANKS , ?MARK?

 

[Hennysemitara]

reeds?

 

[gm280]

First thing you need to do is stop.

Any time you have an engine that isn't running, you have to determine if it is fuel or spark. And that is after you know for certain the timing is not off. If the flywheel sheared a key, there is no way the engine will crank and run. So verify the flywheel and key is in tact. Then start with the spark to verify a quality blue snappy sounding spark. The best way to determine that is with a spark tester like this;


Set the spark gap at 7/16" (there are markings of teh tester) and verify all cylinders are firing correctly. You can buy one of these testers at most any autp parts store for less then $10 dollars. If the spark is good on all cylinders, then move on to the fuel delivery issue. If you have fuel to the carb(s), good. If there isn't a good steady fuel flow, then check the fuel pump. But when you are trouble shooting anything, you have to stay on one thing and not jump all around. That only confuses the issue. Go with a common sense method and you will find your problem(s). JMHO

 

[steelhorse1369]

Reeds have been checked there ok, plenty of fuel, carbs have been rebuilt, fule and vacuum lines all replaced, new fule pump,new fuel supply line and primer bulb and fuel line tank and motor fittings carbs drained and new marine fuel ,sprayed fuel into carbs while trying to start just stalls and plugs come out wet , checked choke to make sure working properly , new coil installed , flywheel checked shear key ok , pistons checked for top dead center with timing marks on flywheel spark is consistant but more yellow than bright blue , next is power pack i guess . Thanks , Mark

 

[jakedaawg]

Istead of throwing parts at it, why don't you just peoperly diagnose.

Did you check spark with an open air gap spark checker set to 7/16" on each cylinder, yes or no?

 

[Tim Frank]

^^^^^ +1.
See posts #s 3 & 5.

Have no idea what you mean by "shear key OK".
How did you "check flywheel"?