WOT Sputter

[Makko]

I have a 1985 50hp Johnson it runs great until I run it at full open, then I can hear it sputter a little. If I back off just a little it runs normal. Any ideas as to what could be the cause of this?

 

[snuffyzz]

Re: WOT Sputter

air to fuel ratio, try adjusting the jet.

 

[petryshyn]

Re: WOT Sputter

To eliminate a fuel pressure issue, try squeezing the primer ball when its sputtering. If it cures it, its a fuel supply problem (restriction in tank, hose, filter, fuel pump issue etc.)....The main jets could also be partially plugged. Try engaging the primer when the sputtering occurs. If that cures it briefly, its a fuel starvation issue.<br />If the above doesn't affect it,I would go through the synch and maximum timing adjustments as well....

 

[Makko]

Re: WOT Sputter

Thanks, Snuffyzz and Schematic!!! <br />I will try the squeezing the primer ball when it sputters.I have located the original owners manual that came with the motor, its a little molded and tattered but I can still read it. I notice it refers to a section called "engine over speed". It says the ignition system is equipped with a limiter circut to help prevent engine damage due to overspeeding. If the engine overspeeds the limiter circuit will activate causing the engine to run roughly or misfire. This sure seems to be what it is doing. I think maybe the limiter needs adjusting. Does anyone know if this can be done and where it is located or how to do this? <br /> If anyone needs a scanned copy of a 1985 40/50hp Johnson VRO I would be more than happy to e-mail it to you. -I know these things are hard to come by. xray_74134@yahoo.com

 

[petryshyn]

Re: WOT Sputter

Hi Makko<br /><br />do you have a tach on board? If so, what RPM does it go up to before misfire?

 

[G DANE]

Re: WOT Sputter

Hi Makko<br /><br />I just mailed you<br /><br />Which boat is this motor on, and which propeller do you have. Maybe that is the problem.<br /><br />Dane

 

[Kuni]

Re: WOT Sputter

start with the basics first before ripping into it you could just have a ht lead breaking down or a bad plug,although rev limiters will give the symptoms you describe and no they aren't settable but on some engines you can cut the wire for racing purposes but i wouldn't recommend doing it.

 

[Makko]

Re: WOT Sputter

No tach on board at this time..I plan to put one on in the next few days. I took it out for a test run yesterday (and some fishing) I could give it full throttle until it got up to speed then it started sputtering. I think it must be the limiter. I do need a tach so I can check the RPM at WOT/full speed. I will scan the manual tonight and sent it out. Thanks all<br />for your help

 

[petryshyn]

Re: WOT Sputter

Don't get carried away troubleshooting until you check the RPM....