So I have been struggling with my old merc for a while. I have determined compression is good and spark is good. The motor is still hard to start, surges under load, and will die at full throttle, so I'm not looking again at the fuel system. This has a Type "B" carb with the built in fuel pump. I have taken it apart a couple of times, but will do so again, but I have a couple questions about things I have noticed that are not right.
1. There is a brass screw on top that is too tight for me to remove. On exploded diagrams I have seen 2 things. Either a cap over the idle tube or the idle tube itself. When I try to remove it with a screwdriver, the top starts to break off, so I have not removed it. The part appears to not be available, so I am reluctant to work too hard to remove it. Is it important for proper cleaning to remove this and blow it out?
2. There are a couple different rebuild kits. Some are just gaskets, and some include some metal parts. Sierra 18-7007 just has gaskets, and 1399-5199 includes some metal parts. The price difference is ~$7 vs ~$65. Do I really need the more expensive kit to rebuild this properly?
3. My carb does not include the fuel filter in the input bowl. I have no fuel filter at all as far as I can tell. Is this filter important or is there a better in line filter to use?
4. How can I tell if the fuel pump is functioning properly? It will idle for a long time, so I know it is pumping, but has trouble at high speed which could be due to a lack of fuel flow. How do you measure this?
1. There is a brass screw on top that is too tight for me to remove. On exploded diagrams I have seen 2 things. Either a cap over the idle tube or the idle tube itself. When I try to remove it with a screwdriver, the top starts to break off, so I have not removed it. The part appears to not be available, so I am reluctant to work too hard to remove it. Is it important for proper cleaning to remove this and blow it out?
2. There are a couple different rebuild kits. Some are just gaskets, and some include some metal parts. Sierra 18-7007 just has gaskets, and 1399-5199 includes some metal parts. The price difference is ~$7 vs ~$65. Do I really need the more expensive kit to rebuild this properly?
3. My carb does not include the fuel filter in the input bowl. I have no fuel filter at all as far as I can tell. Is this filter important or is there a better in line filter to use?
4. How can I tell if the fuel pump is functioning properly? It will idle for a long time, so I know it is pumping, but has trouble at high speed which could be due to a lack of fuel flow. How do you measure this?