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  1. Grumpy Bear

    Newbie question about testing voltage with a DVA!

    Below is what the CDI troubleshooting manual says I need to do to test ignition voltage on my 1974 Mercury 500 50hp. I made my own DVA to connect to my multimeter. However, as any good noob, I have questions! (1) What setting should I put my multimeter on? DC 200? More? Less? (2) So I have 2...
  2. Grumpy Bear

    Who knows about selenium plate rectifiers?

    1974 Merc 500 50hp. At some point, I took apart my rectifier (which, as it turns out, is a selenium plate rectifier). I'm not sure I reassembled it correctly -- lots of washers and spacers, etc. Now my motor runs very rough at idle and bogs at throttle up. Timing, carbs, compression all...
  3. Grumpy Bear

    I think my switch box is fried... or am I not testing this right??

    Motor has been running very rough, won't idle right, dies when you try to throttle up in gear. Decided to check the switch box. So, the first pic is what the manual says the ohm readings should be. I set the ohm meter to 1K as directed. When I test, the readings are OPPOSITE (and still not the...
  4. Grumpy Bear

    Take a look and listen -- see if you can help me diagnose the problem!

    Thanks ahead of time! Couple of short video clips to watch/listen to if you can. Motor is "warm" and warm-up throttle is now all the way off. Choke is off. So, I have: - Link & synced (at least 3 times to make sure) - Carbs are clean and set to spec - Turned out the carb idle screws about 1.25...
  5. Grumpy Bear

    74 Merc 500 50hp, pee hole question...

    When water leaves the water pump and up the copper pipe into the powerhead, here's my question: is some of it designed to flow back out down around the exhaust tube (down through the lower unit) and some eventually through the pee hole? I was testing the flow of water going through the motor by...
  6. Grumpy Bear

    '74 Lightning Energizer ignition -- help with rotor and cap???

    See pic. I'm guessing the rotor must come off before I can remove the rest of the cap? Either way, obviously, both must come off, and it's stuck on pretty tight. I have a wire (white or blue, not sure which) that is shorting and need to get to them underneath. The plastic is old, combined with...
  7. Grumpy Bear

    Gotta scratch I'm not sure how to itch.....

    1974 Merc 50hp 500. See pic. First time the case has been opened in 41 years. Actually didn't realize that a scratch in my cylinder #4 was this significant until I started honing (as odd as that is -- 220# hone, about to finish with 320#). Replaced the piston and rings for this cylinder already...
  8. Grumpy Bear

    Please judge my cylinders!

    1974 Merc Thunderbolt 50hp. The #3 cylinder had no compression (pic 1) but the rings were stuck and scored when I opened it up. Had to dig them out. Noted a broken reed which probably caused this issue. The other cylinder (pic 2) had great compression but still stuck rings (1 of which I had to...
  9. Grumpy Bear

    Lower end cap... check valve??

    '74 Merc 500 Thunderbolt. I noticed this hole when I took off the lower end cap -- nothing in it and light and air blows right through. Then I see on some diagram that there is supposed to be a tiny check valve in there?? What is the purpose of that? Is there supposed to be a check valve in...
  10. Grumpy Bear

    Piston ring compression tools

    74 Merc 500 50hp. So, can you reinstall the pistons into the cylinders with standard piston ring compressors (like pic?), or do you have to have the special Merc ring compression clamps to get the job done (pic of 3) ? Thanks again! Kevin
  11. Grumpy Bear

    How the #@%! do you get this bearing off??

    While I have the powerhead on my 74 Merc 500 50hp cracked open, I thought I would replace the seals and bearings in the upper and lower end caps of the crankshaft. I got the lower cap off just fine, but I'll be a son of a gun if I can figure out how to get the bearing out of the thing (see...
  12. Grumpy Bear

    Replace this piston?

    Hello all. I'm rebuilding the powerhead of a 1974 Merc 500 50hp. One of the pistons I know I need to replace (and not just the rings). Another, however, had good compression but when I looked at it, it was pretty scuffed up (it was next to the other piston that was pretty much fubar). I've...
  13. Grumpy Bear

    What is THIS??

    br1975 Mercury 500 50hp. See attached pics. A tiny little hose connected from the lower to upper powerhead broke (one pic shows where it broke, the other where it is connected on the lower end). With the motor running, it will only idle at full choke and fuel is spraying from the broken hose...
  14. Grumpy Bear

    1975 Merc starts up, runs great, warms up, but then won't restart?

    So, my 1975 Merc 500 50 hp starts right up, runs great, warms up, but then won't restart (or has a very hard time starting back up) after it has been shut off for a few minutes. Here is what I've done so far: new gas (no ethanol), gas additive (Quickleen), new fuel pump kit, new sparks. I have...
  15. Grumpy Bear

    75 Merc 50 hp carb rebuild advice?

    I'd like to attempt a carburetor rebuild on my 1975 Merc 500 50 hp. Anyone know of a good source to guide me through the process? Video was be great, but not necessary. I have a service manual, but it's not that detailed. For anyone who has done this, any advice? Never attempted this before...
  16. Grumpy Bear

    Soaking fuel pump check valves?

    I'm cleaning and replacing the gaskets on the fuel pump for my 1975 Merc 50 hp. Should I also clean the check valves? They have that diaphragm in them, so I don't know whether including them in the soak would be a good idea or not. Thanks!
  17. Grumpy Bear

    1975 Merc 50 hp fuel pump cleaning questions...

    Hi all. Brand new here and a first time boat owner. I am replacing the fuel pump gaskets on my '75 Mercury 500, and I was wondering about 2 things: (1) I am soaking the fuel pump housing in solvent, but I didn't put the check valves in because I didn't know if it was okay to soak them in...
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