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  1. Bradmph

    74 Merc 850- Dash Gauge Wiring & Grounding

    Wiring Dash Gauges and Items to Power and Ground. * I am wiring up a dash on an older Glastron and have replaced all gauges except the MPH gauge. The gauges list I have are...Tach,Fuel,Volts,Amps & MPH. Instead of running the dash cluster off of the main pos cable from the battery to motor, * I...
  2. Bradmph

    Do I need a thrust bearing with this new prop?

    I bought a new prop for my 74 Merc 850 and it came with a brass insert adapter that is used to hold onto the splines. This adapter that fits inside the new prop is a pretty healthy piece of brass. The designing of it looks like it serves as an adapter for the prop with an added thick front plate...
  3. Bradmph

    '74 Merc 850 control boxes universal with a '77 Merc 850?

    I had a '77 Mercury Thunderbolt 850 OB motor and controls and I am replacing motor with a '74 Mercury Thunderbolt 850. Are these control boxes universal with each other? They look the same basically, except the '74 is white and the '77 is black. Thanks
  4. Bradmph

    2-Stroke of Luck - '74 850 merc. Ser#3870882

    Finally I have a working engine that will bolt right up and take the place of my problem'd Thunderbolt 850/canadian. This TB850 loved the garden hose , but was afraid of the lake water and looked like it was just taken off the showroom floor. I put too much money into her and she didn't respect...
  5. Bradmph

    77 Merc 850 - Water puddled on exhaust plate

    The boat has not ran well, so I checked plugs and found tiny water droplets on plugs. Mostly on No.4 and just around the edge of the plug. I decided to remove powerhead to see if I can locate the problem. After removing the powerhead, I found water puddled in the exhaust plate in the driveshaft...
  6. Bradmph

    Merc 850 - Removing Powerhead>Shift linkage question

    Hi, I have a 1977 Merc 850 and I am removing the powerhead. I have everything removed and I noticed when lifting the head up, the shift linkage connects to a shift shaft that goes down to the lower unit. To remove the upper arm off the top of the shaft in the front of the engine...
  7. Bradmph

    '77 Mercury 850 fuel pump issue

    I think I am having a fuel pump issue with my '77 850 thunderbolt. I can squirt fuel into carbs and the boat starts right up, runs for about 20 seconds and stops. I removed the fuel pump and the filter was clean and the diaphram was ok, though it was a little bit stretched from the pressure put...
  8. Bradmph

    1977 Thunderbolt Choke Troubleshooten

    This is a plunger choke design and I have replaced the plunger. After locating the proper wire for the choke, by way of clicking the control box choke button while key switch is on and reading voltage from the required engine wire. I connected the wire to the choke selonoid and then retried the...
  9. Bradmph

    Need Some Torque Specifications -`77 850 Thunderbolt

    I am in need of tightening torque specifications for crankshaft replacement on a `77 Mercury 850 Thunderbolt. I only need the torque specs for the crankshaft replacement and parts connected to the crankshaft that require torque settings. See image below
  10. Bradmph

    Outboard Motor Mounting

    Hi, I own a 1964 Glastron Futura 500 that originally came with an 88hp OMC 488. The prior owners had several issues with the motor and outdrive, so we decided to remove it all and replace it with a 1977 Mercury 850 Thunderbolt. At this time I am repairing the transom by using marine grade...
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