Page last updated July 17, 2008



Carburetor Schematic

Mercury 650 Carburetor Rebuild

OK, here we have an old Mercury 650 circu 1975. It has 2 carbs and they are difficult to remove. A bit more challenging than the 700. You will have to be careful with this one due to the many components that must be removed in order to get to the carbs.

Used, old, but fairly well maintained.

When I first received this engine, it started right up, but shook badly and smoked quite a bit. The first thing I check was the impeller. No water out of pee hole, fixed that but then seals broke and started to leak lower unit oil into water tank.

Oh well, at least it pisses now, back to the first problem. Bad vibrations. First, in order to minimize shaking, I tightened motor mounts and it improved to a much better condition. Then, I inspected carbs and the idle screws were all whacked out.

One screw was 1/4 out of slightly seated (lean condition) and the the other was 1 1/4 out (ok). I went ahead and dissassembled the carbs.

FIRST things first!!! BE SAFE

Remove / disconnect all power supplies. No need to get electrocuted / executed.


Equipment needed:

  1. Basic tools - wrenches / wratchets / screwdrivers
  2. plastic organizer for various small parts (rubbermaid, etc)
  3. plenty of shop rags
  4. couple of plastic bags
  5. carburetor cleaner
  6. gasket remover (available in aerosol can)
  7. carburetor gasket set or repair parts kit / replacement parts set (see,
    This is what the proper carb kit looks like
  8. gasket sealant, dressing / prep (needs to be for carburetor, fuel resistant)
  9. new fuel lines, various sizes based on removal (better to replace)
  10. compressed air (can or compressor)
  11. Safety goggles and breathing mask
  12. Patience

When all power has been removed follow the steps below.

1. remove carburetor cowl and cover.  
2. Open throttle and gear cable retainer.
3. Pull cables out as the seat that is on front cover will be out, cables will stay in place. Simply opn latch, no need to actually remove cable assembly, just pull out slightly.

Continued on page 2


  About Us | Site Map | Privacy Policy | Contact Us | ©2005