nazmen1
Seaman Apprentice
- Joined
- Jan 23, 2009
- Messages
- 39
1979 Merc 402 - - engine was not working for a couple of years. With the help of forum narrowed the initial problem down to a bad switchbox and some brittle and oxidized wire. Replaced the switchbox with a new CDI unit and replaced all bad wiring in the wiring harness, all wiring up to the frame in the stator.
Rebuilt the carbs.
Cleaned the screen on the fuel filter
Replaced the fuel diaphragm.
Replaced the water pump impeller.
Fired the unit up last week and it ran fine in a barrel. Cool and smooth operation on both cylinders with plenty of water discharging from the water pump. This 1st time I did not take the RPM over 2000 since I was running it in a barrel and was in neutral and frankly the engine has not run for a few years.
This weekend I ran it again. I tried to run it past 2000 RPM in neutral and the engine started to miss. Its not healthy to run the engine in neutral at higher RPM but it wouldn't even get past 2000 RPM. I can't take it out on a lake yet because its still too cold where I live in Western NY, so I am not sure if the problem will go away when the engine is run in gear at wide open throttle. But given the way it started to miss I believe there is a problem.
1. The carb was clean when I took it apart with very little sediment or residue in the bowl or jets. I did however soak all the parts just to be sure. So I am ruling out the carb.
2. The engine runs smooth on both cylinders at low rpm.
3. Articles in the forum suggest that it might be the high speed winding in the stator. I put a Simpson meter set at AC on it yesterday, I don' t have a DVA, and the voltage was reading 20+ on the high speed winding but did not substantially increase as the RPM increased, leading me to believe there might be a problem here.
Thanks.
Rebuilt the carbs.
Cleaned the screen on the fuel filter
Replaced the fuel diaphragm.
Replaced the water pump impeller.
Fired the unit up last week and it ran fine in a barrel. Cool and smooth operation on both cylinders with plenty of water discharging from the water pump. This 1st time I did not take the RPM over 2000 since I was running it in a barrel and was in neutral and frankly the engine has not run for a few years.
This weekend I ran it again. I tried to run it past 2000 RPM in neutral and the engine started to miss. Its not healthy to run the engine in neutral at higher RPM but it wouldn't even get past 2000 RPM. I can't take it out on a lake yet because its still too cold where I live in Western NY, so I am not sure if the problem will go away when the engine is run in gear at wide open throttle. But given the way it started to miss I believe there is a problem.
1. The carb was clean when I took it apart with very little sediment or residue in the bowl or jets. I did however soak all the parts just to be sure. So I am ruling out the carb.
2. The engine runs smooth on both cylinders at low rpm.
3. Articles in the forum suggest that it might be the high speed winding in the stator. I put a Simpson meter set at AC on it yesterday, I don' t have a DVA, and the voltage was reading 20+ on the high speed winding but did not substantially increase as the RPM increased, leading me to believe there might be a problem here.
Thanks.