50 HP Johnson motor

[MJWX]

i have a aprox 1978 50hp johnson outboard on a 21 ft pontoon boat that i bought used. starts and idles good and when running the carb linkage by hand at the dock it revs way up. as soon as i shift it to forward it will only go about 1/4 throttle and acts like it is not getting gas. acts like it wants to just take off and go but will bog down. have a new gas tank.hose,fuel filter,plugs. have tried adjustig cables and ses to make no diff. summary. sitting at dock runs great, under power it has no power

 

[jim dozier]

Re: 50 HP Johnson motor

There could be a number of things going on. Just because it revs up in neutral doesn't mean much. You could be down 1 cylinder. Try pulling spark plug wires 1 at a time to isolate a bad cylinder. The one that makes no difference when it is pulled is bad. Or, you could have crud in your high speed jets and need a carb overhaul. Or, your fuel system isn't up to snuff, does pumping the fuel bulb help, does choking the engine help. If none of this works you need to do a compression test on the engine and report the results.

 

[JB]

Re: 50 HP Johnson motor

You are running on one cylinder, MJWX.<br /><br />1. With no load it will pretend to be running great on only one.<br /><br />2. NEVER rev a 2 stroke engine high with no load. High risk of runaway and grenade effect.<br /><br />Spray a bit of fuel mix (not starter fluid) into each carb at idle. Does one of them suddenly pick up rpm? If so, you have a carb problem.<br /><br />Pull each plug wire at idle. Does one kill the engine and the other have no effect? You have a dead cylinder. Check spark and let us know what you have found.<br /><br />Good luck.