Dabbler_E
Petty Officer 1st Class
- Joined
- Apr 20, 2009
- Messages
- 338
After a frustrating (but fortunately not TOO expensive) diagnostic journey, my 1979 Johnson 70 is now running like a ..... sexually-assaulted simian.
Details are HERE. After replacing fuel lines and tank and cleaning/rebuilding carbs, wouldn't run right. With just me in the boat it would plane OK but had real low power at WOT, and with the family in it it would barely plane at all even trimmed way down. Idled fine, but just bogged when punched the throttle. Installed fuel pressure gauge -- showed 3-4 psi = good. #2 plug consistently wet, 1 and 3 fine. Replaced the coil BEFORE doing a real thorough spark check -- mistake 1.
Problem remained. Thorough spark check showed good spark even when hot, but in the process I stripped #2 plug hole threads -- mistake 2.
Tashasdaddy suggested plugged carb jets, but that didn't seem right as a cause of one rich/wet cylinder. However, it did get me thinking seriously about carbs. Other bits of info started clicking in my brain at this point: the motor tended to gain power gradually the more it ran at high-ish rpm, and power tended to jump up when going over a wake (suggests fuel level problem). Gas was bubbling up to the surface at idle. Took off the air cover, and #2 carb had fuel dribbling down from the front. After persuing this forum quite a bit, I found several similar instances of the same syndrome, most due to 1 FLOODED cylinder. The fact that I had already done the carbs blinded me to the possibility that it's a carb problem -- mistake 3.
So, first thing installed a helicoil to repair spark plug hole, then re-tore down carb #2 and yep there was a bit of debris in the needle float valve. Replaced needle and seat, soaked in cleaner, reassembled.
This AM: punched to WOT beautifully, maxed 5400 rpm. Zoom!
This forum is extremely helpful! Glad I found it, and hope this helps others.
Details are HERE. After replacing fuel lines and tank and cleaning/rebuilding carbs, wouldn't run right. With just me in the boat it would plane OK but had real low power at WOT, and with the family in it it would barely plane at all even trimmed way down. Idled fine, but just bogged when punched the throttle. Installed fuel pressure gauge -- showed 3-4 psi = good. #2 plug consistently wet, 1 and 3 fine. Replaced the coil BEFORE doing a real thorough spark check -- mistake 1.
Problem remained. Thorough spark check showed good spark even when hot, but in the process I stripped #2 plug hole threads -- mistake 2. Tashasdaddy suggested plugged carb jets, but that didn't seem right as a cause of one rich/wet cylinder. However, it did get me thinking seriously about carbs. Other bits of info started clicking in my brain at this point: the motor tended to gain power gradually the more it ran at high-ish rpm, and power tended to jump up when going over a wake (suggests fuel level problem). Gas was bubbling up to the surface at idle. Took off the air cover, and #2 carb had fuel dribbling down from the front. After persuing this forum quite a bit, I found several similar instances of the same syndrome, most due to 1 FLOODED cylinder. The fact that I had already done the carbs blinded me to the possibility that it's a carb problem -- mistake 3.
So, first thing installed a helicoil to repair spark plug hole, then re-tore down carb #2 and yep there was a bit of debris in the needle float valve. Replaced needle and seat, soaked in cleaner, reassembled.
This AM: punched to WOT beautifully, maxed 5400 rpm. Zoom!
This forum is extremely helpful! Glad I found it, and hope this helps others.