stevewolverton
Petty Officer 1st Class
- Joined
- Mar 30, 2008
- Messages
- 262
Hi All,
I'm hoping someone could help me troubleshoot a problem with my motor (1983 70HP Johnson) that I'm having.
My motor seems to have a hard time holding idle until it warms up. My tach bounces from 800-1500 or so while at idle. Now here's the strange part - when I get the boat off the trailer, I hit the throttle and only get to about 4000 rpms. The boat planes, and then after a minute or two, the engine kicks hard into full power. Today it kicked into full power, and then cut back after a second. Then about 5-10 seconds later it kicks into full power, and then it backed off again. It did this a few times until it started running correctly. I noticed today everytime the motor would hit full throttle, a puff of smoke would be left behind on the water. I'm guessing this is a cylinder that's not picking up, and the puff of smoke is the burnt fuel/oil when the cylinder fires?
Here's the strange part - after the motor finally gets warmed up and running at full power, it will stay running fine the rest of the day. This only happens at startup. The rest of the day it purrs along at 800rpm in gear.
I've changed the plugs. I've ordered 3 carb rebuild kits (although I'm guessing it's not a fuel delivery problem), and my hunch is a coil. I'm wondering if the coil begins working after it warms up? I'm going to pull one plug wire at a time tomorrow and see if I can find if there is a cylinder that's not firing. I don't know a lot about motors, and I'm hoping that someone here might mentor me as to my next course of action? I do have the FSM.
Thank you!
I'm hoping someone could help me troubleshoot a problem with my motor (1983 70HP Johnson) that I'm having.
My motor seems to have a hard time holding idle until it warms up. My tach bounces from 800-1500 or so while at idle. Now here's the strange part - when I get the boat off the trailer, I hit the throttle and only get to about 4000 rpms. The boat planes, and then after a minute or two, the engine kicks hard into full power. Today it kicked into full power, and then cut back after a second. Then about 5-10 seconds later it kicks into full power, and then it backed off again. It did this a few times until it started running correctly. I noticed today everytime the motor would hit full throttle, a puff of smoke would be left behind on the water. I'm guessing this is a cylinder that's not picking up, and the puff of smoke is the burnt fuel/oil when the cylinder fires?
Here's the strange part - after the motor finally gets warmed up and running at full power, it will stay running fine the rest of the day. This only happens at startup. The rest of the day it purrs along at 800rpm in gear.
I've changed the plugs. I've ordered 3 carb rebuild kits (although I'm guessing it's not a fuel delivery problem), and my hunch is a coil. I'm wondering if the coil begins working after it warms up? I'm going to pull one plug wire at a time tomorrow and see if I can find if there is a cylinder that's not firing. I don't know a lot about motors, and I'm hoping that someone here might mentor me as to my next course of action? I do have the FSM.
Thank you!
