1978 johnson 70etl78c running issues need help please

[Anno]

hi all im only new to this forum so any help would be good i recently bought and old coast guard boat with an old 1978 70 hp on it when i got it was told carbys and water pump had been changed and since then wouldnt run, I found broken earth wire from motor so replaced + and - cables also replaced throttle and gear cables as well at same time got it running and found it wasnt charging the battery and had a missfire so replaced stator and reg/rectifier and coils. So now it starts on choke and idles well charges the battery at 13.9v and is good.
So now ive got it going put boat in water on the weekend for the first time (new fuel new fuel filter new hose and new tank) so starts in the water and idles beautiful but as soon as i try to throttle from a nice putt along it dies did a sink link on the water didnt help then i found if u press key in for choke as u throttle boat takes off get on plane and runs really well u can speed up slow down cruise no probs but as soon as u cruise at 4-10 knts for extended period gets rough and stalls but will start easy again so now i have replaced fuel pump and plugs checked compression and i have 145 psi in all cylinders i believe its fuel mixtures but how do i set them or can some one show me a link to rebuilding the carbys and setting mixtures thanks

 

[5150abf]

Re: 1978 johnson 70etl78c running issues need help please

Welcome to iboats.

Sounds like high speed jets, ti will start and idle because that is a different circuit in the carb but as soon as you open the throttle the high speeds are plugged and the engine isn't getting enough gas, that is why it will run with the choke on.

They are in the bottom of the float bowl way behind the drain screw and you will need a really long skinny screw driver to get them out, run a stripped stranded wire though them and replace and you should be good.

The tinniest speck of anything will plug them so it doesn't mtter that they were just cleaned, could be a peice of hose from when you changed them, i would get a fual filter on it as well.

I run a cheapy Autozone inline filter and haven't had any carb problems for a long time.