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    Bolt length and thread pitch

    Screw and bolt are often used interchangeably. Machine threads can mean fine or course, but not tapered threads like threaded pipe. Sometimes the parts list will give a bolt size, and sometimes bolt length. You can measure the depth of the threaded hole and usually see whether the threads are...
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    No spark

    The shift assist only kills spark to 1/2 the cylinders, as do the overheat sensors.. The kill switch obviously kills spark to all the cylinders. Pull the black/orange or black/yellow wire off the kill switch and ignition switch, plus the overheat sensors and see if spark returns.
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    Bolt length and thread pitch

    Gee, American bolts are usually standard USS (fine) or SAE (course) thread. If you know the diameter, there are standard TPI for each bolt. i.e. SAE thread 1/4" bolt is 20 TPI. 5/16" bolt is 18 TPI. You might try to find out the grade of the bolt. A starter mount may require a stronger bolt...
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    Carrier bearing cracked

    You might price/source a new gearcase from SEI. Their complete gearcases often sell for less than retail purchase of gear sets and bearings.
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    Exhaust Discharge

    OMS is Oil Metering System. They are sometimes called VRO2, except OMS is a constant 60::1 ratio. I am pretty sure your motors have that kind of oil pump.
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    Kill switch removal

    Kill switches only have 2 wires. You have more. OEM Johnson OB ign switches will accept a kill lanyard, but will also work fine without one. On those, when the lanyard is pulled, the ign switch is physically turned CCW to the off position. I cannot see if that is what you have, but it looks...
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    Exhaust Discharge

    Those OMS motors will use more oil if there is an air leak in the gasoline supply to the motor. Check the main strainer O ring and gasket, as well as any other connections in the fuel line that could suck air.
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    Fuel tank

    If you drain and clean out the permanent tank, you can leave it in the bilge unused and use another fuel tank. Make sure the new fuel tank is USCG approved.
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    Deck plate question?

    Mike, your fuel tank is in the bilge, right? Your bilge is not sealed, so no second level of protection....sorry. In rough seas I have had water splash out of the bilge onto the top of my sterndrive engine, causing it to stall. The engine had a plastic water deflector over the carb, plus a...
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    Fibreglass boat floor replacement - do I need to use fiberglass?

    Epoxy is not necessary for that type of repair. You do need to use polyester resin and cloth, however. Resin and polyester putty are available at marine stores and even the Home Despot. Cloth is available usually only at marine stores. Replace any rotten stringers or frames with dry, solid...
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    Deck plate question?

    If water still leaks into your tank, sealing the deck plate is not the remedy. Water can splash onto the tank from the bilge, and possibly other places. The tank must be sealed, and if so, sealing the deckplate is a nice to have, but not absolutely necessary.
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    50HP Mercury Thunderbolt Stalling

    I have not worked on your exact engine, however, Mercury's of that vintage need a richer idle mixture to allow them to accelerate. Modern marine mechanics do not know this, so they set the idle mixture to give a smooth idle. That setting is too lean. The next time you are out on the water...
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    2 stroke motor went underwater - what to do

    Saltwater or freshwater? For either, you must leave it underwater until you can work on it and completely fix it. Saltwater immersion means complete disassembly. Saltwater often ruins electrical parts as well. Starter would need disassembly and cleaning, in addition to engine block...
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    Pontoon in the snow

    I have pulled my boat out in December, where I had to break 1/8 ice on the creek, with the hull. It cleans the bottom and removes that nasty antifouling paint build up.
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    Can I convert a 5 terminal ignition switch to a 3 terminal ignition switch on the dash.

    You will also need to wire the power to the starter solenoid thru the neutral safety switch, located in the control.
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    Hot cables and starter when cranking

    Are those battery cables are 35 years old? They could be corroded under the insulation. If cleaning the ends doesn't fix it, new cables could be in your future.
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    Can I convert a 5 terminal ignition switch to a 3 terminal ignition switch on the dash.

    Normally the motor harness connects directly to the ign keyswitch. An inline fuse is installed on the battery wire at the motor, to protect the engine. This keeps the wiring simpler and less prone to failure due to corrosion or wiring component failure. I am not sure what year Merc you have...
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    changing out a power trim transom bracket 1984 Merc 115 hp inline 6

    You could go on a parts list site like crowleymarine and see if the midsections for the jet and prop versions are the same. In your first post you said you swapped the midsection to get one with PTT. You really meant you swapped the midsection and transom bracket, right? It is too bad...
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    Can I convert a 5 terminal ignition switch to a 3 terminal ignition switch on the dash.

    I have an electric choke set up and preintregrated mercury trim. I looked at universal laynard killswitches and they have the two Ms on them and since grounding out it what kills the engine, could I not run the m wires to the killswitch without running the to the ignition? I suppose you could...
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    Can I convert a 5 terminal ignition switch to a 3 terminal ignition switch on the dash.

    Modern Outboards need the 5 terminal ignition switch. They run on an ADI system, where grounding the "M" wires kills the ignition. They also need an electric choke function.
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