1974 Johnson 50 HP: Runs great till I accelerate

[dcraton]

Motor starts fine, usually first crank. I have replaced fuel lines, cleaned fuel path, cleaned carbs, new plugs, new gas tank, ran Sea Foam through it, used Berryman's, and even spoke nicely to it.<br /><br />I loaned the boat to my dad, and he had to replace the shifting and other cable to the carbs from the console. Since I have gotten it back, it has run so inconsistant when I try to accelerate and it will no longer run at full speed, maybe 3/4 at best and intermittent. Could the linkage on the cable and carbs be out? Or should I look at tearing the carbs down and cleaning those?<br /><br />In a bit over my head here, and thanks in advance.

 

[Brew2]

Re: 1974 Johnson 50 HP: Runs great till I accelerate

I'd start by checking compression on the cylinders. Anything over 100 and within 10% on all cylinders is good.<br /><br />Next I'd check the spark. It should jump a 1/2 inch and be bright blue.<br /><br />Finally, with the motor running, pull each spark plug wire one at a time (use insulated pliers). If the rpms fall off, then you know that cylinder was firing. If there is no change, then that cylinder wasn't making any power.<br /><br />Report back on what you find.<br /><br />Finally, if you haven't already done so, buy the manual for your motor. Makes troubleshooting and repair infinitely easier. It will pay for itself with your first repair.<br /><br />Cheers.