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  1. bobgritz

    Why does engine stall going from high speed to idle ?

    Whenever I cut back to idle speed instantly or abruptly (from anything above 1/3 open throttle) my 15hp Johnson stalls out. But, if I throttle back slowly, it comes down to an idle without stalling. Although I always try to idle down gently, half the time you need to simply cut your speed...
  2. bobgritz

    Is there a home remedy to flush gearcase before changing lube ...

    I'm changing gearcase 'oil' and wanted to do a simple flush first. I haven't done it in about 2 years and it's way overdue (has that mock-burnt smell) and rather than simply change the oil I wondered if there was a home remedy flush anyone uses, for instance, something basic like kerosene?
  3. bobgritz

    I Have Serial # But No Cowling (Cannot Find Year Or HP)

    I have a 70's/80's Mercury with no cowling nor any markings indicating HP. The id plate indicates their typical 7 digit serial number but using their secret codes it could fall between the range of 1001 different motors. It seems infantile to cross reference carb numbers or other miscellaneous...
  4. bobgritz

    Fuel Filter Before Or After Primer Bulb ...

    Does it matter if filter is before or after primer bulb as long as bulb points upward?
  5. bobgritz

    Where Does This Gasket Go ???

    I am replacing pistons in my 1983 Johnson 15hp. The powerhead gasket set has one gasket that doesn't seem to belong! I know extra gaskets are sometimes included for multiple applications but before I go too far I just wanted to see if anyone recognizes my extra gasket. This first picture shows...
  6. bobgritz

    What is correct clearance for reed valves ...

    What is correct clearance for reed valves in my 1983 15hp Johnson? Or, do they just lie flush against the leaf valve assembly plate?
  7. bobgritz

    Scored Piston Causing Engine To Misfire (See Pictures)

    The top cylinder was not firing (at idle) on my 1983 15hp Johnson although at high rpm's both cylinders would kick in. I had 1/2" of spark from both and plenty of fuel. The compressioin tested at 115 lbs each. I rebuilt the carb, replaced coils and powerpack, rebuilt fuel pump then replaced...
  8. bobgritz

    Is There A Site Illustrating The History Of Mirro Craft Boats

    Is there a site that illustrates the history of Mirro Craft boats?
  9. bobgritz

    Are These Reed Valves Seating Properly (Pix Included)

    Here is a pic of the reed valves on my 1983 15hp Johnson. The first picture shows the valves when held at an angle and you can see 'light' coming through a gap between the valve and the plate. Is that normal and acceptable or should the valves lay tight against the plate. I assume it's a...
  10. bobgritz

    Boat Pulling Right OR Engine Pushing Right

    I'd go around in circles if I didn't strongarm my tiller handle. The engine is a 1968 9.5hp Sportwin and the boat is a 14' Starcraft. It's likely a trim problem and not a hull problem since the boat rode true with a previous motor that I just pulled off. I need to emphasize that it's not a...
  11. bobgritz

    Could weak spark be the cause of low power?

    When it runs in a tank it seems to have plenty of power but under load it feels like your towing another boat. It would be perfect if you did nothing but trolling but when you crank up the rpms it struggles to push my 14' aluminum boat. Compression is 60 lbs. in each cylinder. Obviously 80-110...
  12. bobgritz

    Can Cracked Exhaust Cover (or Gasket) Effect Cooling ?

    I always had a nice steady stream of water out the overflow opening (p-hole) but now it just spits and is quite hot. The cylinder head also gets extremely hot. I pulled the water pump which appears to be in normal condition with no obvious signs of wear. I changed the head gasket and there was...
  13. bobgritz

    Anyone Recognize This Gooey Stuff?

    When I separated the gearcase to change my water pump I was greeted by this gooey mess (see pic). I was changing water pump due to cylinder heads running hotter than usual and very little water coming out of discharge port. Not sure if it's related but the engine dies when I pull the lower...
  14. bobgritz

    Trickle Of Water Out My P-Hole ...

    I'm only getting a trickle of water out the p-hole of my '83 15hp ... up until now the head would only get warm to the touch but now you cannot hold your hand on it. I checked for obstructions in the p-hole and the p-hose but they were both clear. I blew air into the p-hose was able to blow...
  15. bobgritz

    Could We Have An EXPERT Discussion Of Basic Carburetors ???

    Could we have a discussion of the basic operation of a carburetor (see below) from expert carb mechanics. The gas/oil mixture enters the bowl by way of the float valve and this is fairly rudimentary but from there it becomes a bit more mysterious. It would seem that the depth (or height) of...
  16. bobgritz

    Foamy Water Spray To Detect Vacuum Leaks ???

    In the past, I always sprayed a carburetor starting fluid (or spray bottle of mixed gas/oil) when trying to find a vacuum leak (RPMs would increase). I recently read a post that mentioned using 'foamy water' to detect vacuum leaks. I imagine this would also cause a change in the rpm's (a drop...
  17. bobgritz

    1976 6HP Needs 1/3 Choke To Idle ...

    This motor was owned by a FD and I doubt it was ever used. It is spotless under the cowling (I hate to subject it to any use, it belongs in Outboard Museum). It runs like a swiss watch at upper RPMs but at idle it stalls out. I took carb apart (didn't take off metal caps) but I did soak it for a...
  18. bobgritz

    How Do I Inspect Reed Valves [15hp]?

    Engine immediately floods out. This engine has been a workhorse for me for over 2 years always starting on first or second pull and idling like a top. Compression is 110 in both cylinders. The first thing I did was to rebuild the carb (removed all caps, soaked it and blew it out) with no...
  19. bobgritz

    Is Head Gasket Sealer Necessary or ...

    I just put on a new head gasket (1983 15hp) and finger-tightened head bolts. It donned on me that I didn't put any sealer on the gasket and when I look in my manual it states "Do Not Use Sealer If So Stated On The Gasket". I don't remember seeing that statement on the gasket but I really didn't...
  20. bobgritz

    Head Gasket Has 'Tiny Bubbles' (see pic) ... What & Why ?

    I am changing head gasket in my 1983 15hp Electric Start Johnson and the head gasket is covered with tiny bubbles. I'm unfamiliar with this condition ... any ideas what caused this and is it normal?
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