1983 Johnson 70 - Dies on throttle up under load

[weavej3]

1983 Johnson 70hp dies moving from idle to WOT only under significant load (ie. pulling skier out of water). Works fine in all other conditions including full load in boat. If I give it choke during throttle up it comes alive. Based on other topics I assume fuel delivery problem but need advice on list of things to check/replace. I assume 1) replace tank and lines 2) rebuild/clean carbs 3) rebuild fuel pump. Is this the correct list and order of diagnostics? I replaced plugs last season but should I be doing a compression test before looking for fuel problems? If I get a shop manual would I be able to clean/rebuild the carbs/fuel pump myself and what manual would you recommend?

 

[rickdb1boat]

Re: 1983 Johnson 70 - Dies on throttle up under load

First in the order would be a compression test to see if the motor is still healthy enough to pull a load. If that checks out, I would move on to the carb. rebuild, as it appears you are getting sufficient fuel supply at all other times. The giving it choke and it comes alive leads me to believe it's carb related. A factory manual will guide you through the carb rebuild just fine.<br /><br /> Manual

 

[jim dozier]

Re: 1983 Johnson 70 - Dies on throttle up under load

How does it idle. I agree you will probably need a complete carb clean/rebuild but I wonder if opening up the idle adjustment a little richer might not fix this. If it doesn't then you need a rebuild. Proper idle setting should be about 1/4 turn richer than the best idle setting to allow for acceleration coming off of idle.

 

[Yepblaze]

Re: 1983 Johnson 70 - Dies on throttle up under load

Go ahead and do a compression check. If less than all close to even pressure do a decarb treatment.<br /><br />Check compression again.<br /><br />If compression very close to equal procede to carb work.<br /><br />Pull carb(s) and pay attention to the actual jet orafices making sure they are clear and not restricted by debris. Remove the jets one at a time and hold up to light while viewing through the hole. Probe them lightly with a piece of wire to dislodge any hardened deposits while making sure you don't scratch or enlarge the hole in the brass.