loss of power under load

[willinfla]

1 have a 1993 johnson 120 v4 vro<br />compression is good. it has ran great until recently. runs fine at slow speeds but when you give it throttle it just wont go over about 3500 rpms. it used to kick up to 5500 to 6000 and jump up on plane.if you take it out of gear it still shots up to 5500 rpms with no problem. help

 

[JB]

Re: loss of power under load

Howdy Will. My troubleshooting program says that the #1 suspect is synchronization of spark timing with throttle opening. In a 2 stroke, at any rpm, torque depends on spark timing. Opening the throttle with no load requires almost no torque. I'm not sure how synch. is done on your 60 degree V4, but on most engines there is a mechanical linkage between the throttle and the ignition system that keeps them in synch. It may have come loose or simply shifted. Hope that helps. Good Luck.

<br />JB

 

[Dhadley]

Re: loss of power under load

You said it ran good until recently. How long ago? Has it sat? Are you sure it's running on all 4 cylinders? Make sure the linkage didn't come loose. The timer base should move as the throttle is advanced until it hits the stop. Make sure both sets of carbs open completely. The 120 is a 90 degree looper with mechanical linkages. When you checked the plugs did they all look the same? Did anything happen like an overheat? Was anything changed like plugs?<br />Good luck!