1963 40HP Johnson -Engine cuts out after awhile in high speeds

[groundswell17]

After about 15 minutes the motor will not run at full speed. it will only run at a little more than idle. If i try and go full throttle the engine cuts out. During the first 15 minutes the engine runs great. any suggestions.

 

[fireman57]

Re: 1963 40HP Johnson -Engine cuts out after awhile in high speeds

Check your spark when this happens you might be losing a cylinder. You can also squeeze the primer bulb to check your fuel pump.

 

[CanWoodsman]

Re: 1963 40HP Johnson -Engine cuts out after awhile in high speeds

Does this happen after you shutdown than restart after a high speed run? If so it may be fuel overheating in the carb bowl and boiling over & blocking the high speed orifice.<br />To check or clear this - remove plugs & ground plug wires without plugs attached and turn over engine aprox 10 revs. Re-instal plugs and try motor. Should operate at full speed.

 

[groundswell17]

Re: 1963 40HP Johnson -Engine cuts out after awhile in high speeds

This happens all the time. It doesn't matter if its shutdown or restarted. Do you think it could be the fuel mixture as well, because the motor will push then give up a bit and then push again like its getting gas then not getting gas. The motor all of a sudden has more smoke/steam coming out of the hole since i've added more gas/oil (24/1). I just changed the thermostat, thinking that the engine was overheating. that didn't work. I'll try both you're ideas tomorrow and let you know. thanks for the info.

 

[fireman57]

Re: 1963 40HP Johnson -Engine cuts out after awhile in high speeds

I believe that this engine should be 50:1 mix. You might just be due for carb rebuilds.

 

[groundswell17]

Re: 1963 40HP Johnson -Engine cuts out after awhile in high speeds

i bought a manual on the motor and it says 24:1 anyway how do i rebuild the carbs.. just take them a part and clean them...

 

[fireman57]

Re: 1963 40HP Johnson -Engine cuts out after awhile in high speeds

No just buy the rebuild kit at your local johnnyrude dealer. Should run about 20.00. Replace the part in the kit that are for your engine. Soak the carb overnight is cleaner and blow all the orafices out with compressed air. It is not a hard job just take your time. The manual will walk you through it. Glad you checked on the oil ratio. I guess it was around '64 they changed it. Do you have the two line pressure fuel tank on this or just the single line with a primer bulb? Check for it overheating. Should be able to hold your fingers on the head for 8-10 seconds before they really start to hurt. There is more to the cooling system then just the thermostat. You could have a small clog in the water jackets or your impeller could be worn. I would take a buddy and a timing light out with me next time and when it does this have him check for spark on each cylinder. Could be overheating a coil and losing it. You can also check for overheating on the same trip. If you have a primer bulb you can squeeze it and see if that helps also. When you do these last three things post back the results.

 

[groundswell17]

Re: 1963 40HP Johnson -Engine cuts out after awhile in high speeds

ok..i haven't had time to rebuild the carbs but this it what i have done so far. I did a new mixture of gas, added new spark plugs and seemed run a little better but not much. I then added some fuel cleaner and also sprayed some carb cleaner down the choke throat(or air intake,not really sure what its called). It took about 10 minutes but after then the boat ran fine at high speeds didn't stall out at all. the only problem i seem to have now is when im in idea it seems to stall out. So to me it seems like its the carbs...I'll have to take them apart and clean them. I'll also clean the fuel filter(or bowl)whatever it is.

 

[fireman57]

Re: 1963 40HP Johnson -Engine cuts out after awhile in high speeds

Yes you need to take them apart and put a kit in them and you will be fine. You can't clean them by spraying cleaner in them. The jets need to be sprayed out and be squeaky clean. You might want to soak them. The time you spent spraying stuff and running stuff would have been the same amount of time you would have spent rebuilding and you would be done by now.