Johnson 70hp troubleshooting

[Bill Foote]

1987 Johnson 70hp 3cyl. block:

So, I have been trying to get this engine running and..... not so good

Here is my observations thus far:
1. Carbs are cleaned and bench synched the throtle plates, fuel is flowing to the carbs and they are carbureting as they should do...
2. Reeds are seated and do not appear chiped, broken, or bent.
3. compression is 130, 128, 129 respectively
4. nice thick blue spark on each plug.

So whats wrong then???
1. After cranking the engine with a good charged battery and fresh fuel, the engine doesn't run, maybe a pop now and then...
2. Cover carb throats with rag while cranking to flood them out.. still nothing
3. Removed spark plugs after flooding carbs... Bone dry

Conclusion:
Fuel is not getting to the cylinders, but it is flowing to the carbs...

Suspicions:
1. Upper and/or lower crank seals are leaking

2. Is there supposed to be a gasket in between the 2 crankcase halves or is there an oring seal?
3. Can the upper crank seal be replaced without tearing the powerhead all the way down?
*4. If the seals were bad on the crankcase, would you still have good vacuum on the throats of the carbs?
5. Could the exhaust system be clogged???

Any suggestions?

Thanks in advance

 

[JB]

Re: Johnson 70hp troubleshooting

Try squirting some premix fuel into the carbs. I don't think that will do any good, but you need to verify that the problem is not fuel starvation.

If all three carbs are failing you really need to review your overhaul procedure.

I think you may have spark timing trouble, either mixed up plug wires or a sheared flywheel key.

Did you do a link 'n' synch by the book?

 

[Bill Foote]

Re: Johnson 70hp troubleshooting

1. The carbs are working correctly.
2. I tried squirting fuel via modified eye dropper(to ensure atomization), before overhauling the carbs and still observed dry spark plugs.
3. The flywheel key has not been sheared. Contrary to my usual suspicions ignition problems do not seems to be the culprit here.

Next: Currently I have removed the flywheel, my intention is to remove the stator and timer base to inspect the upper crankshaft seal. I plan to globbb it up real good with some super thick grease to see if I can get the engine running again. If this works I will deduce that the seal is bad and would like to know if it can be replaced without tearing the engine apart? Any advice?


Perhaps I should have mentioned this earlier: Prior to me doing anything to it; The engine ran for about 20min. It wouldn't idle very well but would run wide open and would plane the boat. Upon coming off a plane slowing down the engine died and I am now in the process of determining why fuel is not being delivered to the combustion chamber though the carbs are working and getting fuel etc...

I need to know if the crankcase halves are supposed to have a gasket between them or if they have some kind of oring seal or just some silicone? Also, if the crankshaft seals can be replaced without splitting the crankcase?

FYI: this engine has been torn apart before judging by the lack of paint on the bolt heads from sockets and wrenches. Though I don't know what was done or replaced/rebuilt