Gizmobreaker
Seaman Apprentice
- Joined
- Apr 26, 2008
- Messages
- 45
I have a Johnson 15 hp J15RLCOB long shaft on my Catalina 27 sailboat. It has been great for the 4 years that I have owned it, with the exception that it will quit if you go from fast to idle too quickly. I learned to live with it.
This season it has learned a new trick. It will start right up and run fine, then after, say, a half hour it will begin to run slower and slower and finally quit. It will restart but not stay running. When I can get it to run, it will bog almost immediately. When it finally runs, it will bog terribly and stall if when I change throttle position, either up or down. After it rests for a while, it will start up and run up and down, but if I put it in gear it will bog and die. Finally, after much complaining, I will get it to run and it will stay running long enough to get me in to my mooring. I can't say that anything changes except time. The fuel bulb does not collapse.
I have installed 2 new coils and a power pack. The plugs are new and gapped .030". I have changed them 3 times. I don't see any arcing near the coils or the power pack.
Spark gap tester looked great at 7/16". Plugs were in at the time.
The compression is 105 on the lower cylinder and 110 on the upper. 3 pulls.
I rebuilt the carb, yesterday. I installed all the parts from the kit, except for one lead plug (too small for any on my carb) and one small white/clear plastic short stepped tube (no idea what that is for but the kit covers many carbs). No rust in bowl. The entire carb was beautiful. Looked like new. No varnish or deposits, anywhere. No dirt.
Fuel is brand new Mobil 93 octane, mixed 50:1 with new Mercury oil. Gas tank was new last year and stored empty. Brand new vented cap, just in case. Gas hose is OMC, 2 years old. I cleaned it out at the beginning of the season to make sure there were no ethanol snakes. Clean fuel only.
Roller timing is correct by the shop manual. I set the slow speed needle and it was responsive. One thing I'm unsure about. The slow speed needle does not come to an actual point. It has a blunt end. Not rounded but like it was cleanly made that way. Very small, maybe .015". Is that correct?
Other than the slow speed needle, I'm fresh out of ideas. Any help would be most appreciated. I don't want to buy a new motor because this is the only one that will fit the peculiar transom cutout on my boat.
This season it has learned a new trick. It will start right up and run fine, then after, say, a half hour it will begin to run slower and slower and finally quit. It will restart but not stay running. When I can get it to run, it will bog almost immediately. When it finally runs, it will bog terribly and stall if when I change throttle position, either up or down. After it rests for a while, it will start up and run up and down, but if I put it in gear it will bog and die. Finally, after much complaining, I will get it to run and it will stay running long enough to get me in to my mooring. I can't say that anything changes except time. The fuel bulb does not collapse.
I have installed 2 new coils and a power pack. The plugs are new and gapped .030". I have changed them 3 times. I don't see any arcing near the coils or the power pack.
Spark gap tester looked great at 7/16". Plugs were in at the time.
The compression is 105 on the lower cylinder and 110 on the upper. 3 pulls.
I rebuilt the carb, yesterday. I installed all the parts from the kit, except for one lead plug (too small for any on my carb) and one small white/clear plastic short stepped tube (no idea what that is for but the kit covers many carbs). No rust in bowl. The entire carb was beautiful. Looked like new. No varnish or deposits, anywhere. No dirt.
Fuel is brand new Mobil 93 octane, mixed 50:1 with new Mercury oil. Gas tank was new last year and stored empty. Brand new vented cap, just in case. Gas hose is OMC, 2 years old. I cleaned it out at the beginning of the season to make sure there were no ethanol snakes. Clean fuel only.
Roller timing is correct by the shop manual. I set the slow speed needle and it was responsive. One thing I'm unsure about. The slow speed needle does not come to an actual point. It has a blunt end. Not rounded but like it was cleanly made that way. Very small, maybe .015". Is that correct?
Other than the slow speed needle, I'm fresh out of ideas. Any help would be most appreciated. I don't want to buy a new motor because this is the only one that will fit the peculiar transom cutout on my boat.