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  1. merc850

    Simple

    The idea is to de-gum the passages, like using injector cleaner in an auto. Sorry I posted it.
  2. merc850

    Simple

    There's a simple way to check for fuel in the carbs and fuel flow; tilt the motor all the way up then pump the fuel bulb, if fuel runs out of the carb throat(s) then it's probable that all's clear. This can also be used to flush the system. To clean the carb(s) remove the low speed needle(s) and...
  3. merc850

    Grinding going into gear

    Don't shift into reverse without the motor running or; turning the prop while someone shifts. Other things that could be causing the noise: prop is missing Fwd thrust washer causing it to grind on gearcase, carrier nut at front of unit has moved out causing too much play in gears, shift cam or...
  4. merc850

    Grinding going into gear

    Check the cable setup
  5. merc850

    1955 Mercury Mark 40 Help

    Here's another description of the "Quicksilver"
  6. merc850

    1955 Mercury Mark 40 Help

    From a catalog, here's a site that deals in older motors and in the general forum they are talking about a KF9 (early Mark 40). Do you have the fuel tank? https://johnsoldmercurysite.com/phpBB3/index.php
  7. merc850

    1955 Mercury Mark 40 Help

    Another thing use Lubriplate 105 in the gear case not gear oil. Here's a part source including the factory manual. https://www.oldmercs.com/category_s/127.htm
  8. merc850

    1955 Mercury Mark 40 Help

    Do not use 30w motor oil just use Marine oil at 25:1.
  9. merc850

    Murcury 850 thunderbolt ignition tachometer

    Yep just fooling around until you kill the switchbox. Buy a proper tach.
  10. merc850

    New issues on engine

    That looks like a hole for a temp or water pressure gage, I'd plumb in a pressure gage.
  11. merc850

    Murcury 850 thunderbolt ignition tachometer

    That tach could be for a Mercruiser 8 cylinder 4 cycle stern drive; this one should work https://www.marineengine.com/newparts/part_details.php?pnum=MER79-895283Q45
  12. merc850

    Murcury 850 thunderbolt ignition tachometer

    The signal wire runs from ONE of the YELLOW wires on the rectifier, if that's a new tach it probably means 8 poles which will work. What is the serial nr. of your motor? Did you find the tach with the nr?
  13. merc850

    Mercury 850 thunderbolt ignition switch wiring

    The brown terminal on the distributor (3 terminal side) of the switchbox.
  14. merc850

    Mercury 850 thunderbolt ignition switch wiring

    Don't wire a ground to the white terminal it is + when engine is running! You need a kill switch that opens when pulled, a switch that closes when pulled can be wired to the mercury switch side of the switchbox.
  15. merc850

    Mercury 850 thunderbolt ignition switch wiring

    The kill wires don't apply - in this case the motor is stopped by cutting power to the white wire, the black wire is for the tach ground at the plug for the tach.
  16. merc850

    At my wits end

    I think your problem is somebody damaged the carbs - the JB weld is plugging up the welch plug access to the internal passages. New or undamaged carbs might solve the problems.
  17. merc850

    Mercury 850 thunderbolt ignition switch wiring

    The E wire is orange and was used in older models for ignition you don't need it.
  18. merc850

    Mercury 850 thunderbolt ignition switch wiring

    B is + battery, I is white wire, S is yellow, C is gray. M is not used for your ignition.
  19. merc850

    At my wits end

    If you post the serial Nr. and some photos it would really help.
  20. merc850

    1978 Mercury 90hp outboard

    Here's a wiring diagram - I would just replace the wires, the waterpump impeller, the gear lube and not touch the timing. After all that see if it will run. The coil should be available on this site. The switchbox terminal nuts seem to be rusty if so remove and clean the terminals. An AD tach is...
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