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  1. merc850

    1965 3.9hp plug fouls

    That's not the right plug for that motor - J8C https://www.oldmercs.com/category_s/1208.htm
  2. merc850

    Mercury 85HP Thunderbolt Ignition Series??? Whats missing??

    Found this wiring dia. appears that those motors used ADI not a distributor.
  3. merc850

    Mercury 85HP Thunderbolt Ignition Series??? Whats missing??

    I'm guessing that the fuel pump/wiring harness/ignition can't be used in your motor, go have a look at it if you can with cowling off. It might be a 1979 model like this one
  4. merc850

    Mercury 85HP Thunderbolt Ignition Series??? Whats missing??

    Correct! serial numbers 3186263 thru 3493912 were 1972 models.
  5. merc850

    Mercury 85HP Thunderbolt Ignition Series??? Whats missing??

    I have my 850 runner on a boat and I picked up a poorly maintained one for $200.00 which gave me some useful parts, some marinas keep old ones in the "boneyard".
  6. merc850

    Mercury 85HP Thunderbolt Ignition Series??? Whats missing??

    Try John's Old Merc site.
  7. merc850

    Mercury 85HP Thunderbolt Ignition Series??? Whats missing??

    Wiring diagram fuel pump parts the pump originally had brass fittings that the lines attached to (compression type) that are missing from your lines so you'll have to use barb fittings and you'll need the pump body; these people https://www.oldmercs.com/category_s/1702.htm sell the hoses and...
  8. merc850

    1975 Mercury 500EL Lightning Energizer wiring…

    That motor uses a self energizing "magneto" so the white wire just powers the choke and tach as shown in the wiring diagram - it doesn't need 12v to operate. And as Chris said the control harness can be used for many HPs this is the wiring for 8500/1250/1400 etc the white engine harness wire...
  9. merc850

    Did I flood it, did I mis use the remote, was it old fuel, or all of the above?

    Tip the motor all the way forward and fuel will run out of the carbs.
  10. merc850

    Mount Swap

    That system needs to be bled! Doesn't anyone paint those parts before installing them? The lower cylinders use longer rubber bushings that might be still available from a Mercury dealer.
  11. merc850

    Mercury 500 Thunderbolt 50 HP Link and Sync

    Usually a 50 gallon oil drum with the motor on boat: the manual is 1975 thru 1978 part Nr. C-90-75512. For low speed setting you can use muffs.
  12. merc850

    Mercury 500 Thunderbolt 50 HP Link and Sync

    Try these instructions
  13. merc850

    Mercury 500 Thunderbolt 50 HP Link and Sync

    The manual I have (1975-1978) only shows the instructions I've posted but on further inspection I notice that it's for up to serial Nr. 4576236 the posted picture is for ser. Nr 4576237 and above, so much for downloaded manuals! I'm scanning the hard copy now.
  14. merc850

    Mercury 500 Thunderbolt 50 HP Link and Sync

    This should help you have to start on page 1 to do it right and you'll need a timing lite.
  15. merc850

    Merc lower driveshaft needle brg

    This is what I have from the 75-78 manual, I don't think there's a shoulder anywhere at the bottom or top of the housing. Removal is easy; installation is trickier.
  16. merc850

    Merc lower driveshaft needle brg

    We need the year/serial Nr. eg: a 1970's bearing is pressed into the cavity.
  17. merc850

    1985 Mercury 50HP 2-Stroke - Tach Recommendations

    You need an Alternator Driven Tach that connects to one of the yellow leads from the alternator, this is the standard tach today. They sell some on this site https://ww2.iboats.com/Boat-Tachometers/dm/view_id.248010 I went to a Merc dealer and got a "pull" for a few dollars 20 yrs. ago and It's...
  18. merc850

    Mercury red band 1150

    Take the cowlings off and look for a distributor and coil/switchbox. I have the wiring diagram for the 77 which uses the distributor but not a diagram for the red band (69-70)?
  19. merc850

    Driveshaft/pinion gear removal issues

    Check the gear lash - there are shims in there that set it.
  20. merc850

    1974 Merc 9.8 hp

    Is the throttle plate opening all the way up, while engine is not running turn the tiller handle all the way and look into the carb; the edge of the plate should be facing you. Another possibility is the ignition timing is over-advanced which will slow it down. The carb has a fixed hi-speed jet...
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