97 johnson still wont run

[steelhorse1369]

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. 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 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 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 same resul

 

[steelhorse1369]

didnt post entire post try again

 

[steelhorse1369]

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 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

 

[gm280]

Have you tried squirting some 50:1 fuel into the carb openings to see if it cranks and runs for a few seconds? If it does, then I still believe you have a fuel delivery issue. And have you checked to see if the fuel pump is providing a good fuel flow? If you already checked for good spark and it was a solid blue snapping fire, then you have to recheck the fuel issue more. You could also use an induction type timing light attached to one of the plug wires to verify the spark isn't dropping out when it does crank and run for a few seconds. JMHO

 

[kcassells]

You need to post in the johnson engine section. Lots of great guys and VRO experience.
They helped me out a lot. Good luck!! Says I. They'll get right on it.

 

[gsxrdan]

Just saying, i had to change plugs that seemed to be working fine when pulled from the block, but which failed under running conditions, after going through all i could think of i bought new plugs and solved the problem