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  1. M

    Mercruiser 4.3LH backfiring & weird timing

    Are we sure that we are on number 1 cylinder and also have we verified the balancer hasn't spun?
  2. M

    Unidentified wire

    Yeah I realized on my last run that my in dash tach was off by 400 rpm at 4800 rpm so when the dash says 4800 the shop tach reads 4400
  3. M

    Unidentified wire

    Gotcha
  4. M

    Unidentified wire

    Just wanted to make sure The 21p 4 blade I was running 4600 rpm at 3/4 throttle so I didn't go wide open and the 19 pitch 3 blade I was running 4400 @ half throttle so again I didn't really test at full throttle.. it's my understanding that max rpm is 4400-4800 is that correct? The 21p 4...
  5. M

    Unidentified wire

    Thanks
  6. M

    Unidentified wire

    Yeah i knew that a 21p 4 blade was equivalent to a 3 blade 23 and idk how the 4 blade did on the original boat it was on with this same engine i never really went full throttle because i was watching my rpm and i didn't over rev because I made sure to keep my eyes on the shop tach because...
  7. M

    Unidentified wire

    Took the boat out yesterday and it ran great I do have a few questions though as the 4.3 is new to me 1st when I start the engine cold it has 40psi of oil pressure idling and goes up to 60psi while under power and maintains 60psi the whole time under power. But after a 30 minute run down river...
  8. M

    Unidentified wire

    Funny you should say that.. I bought a complete boat with this engine in it and a rotten floor just for the Y-pipes and the upper unit with plans to convert my boat to a 4.3. The guy said that he shut the boat off to pick up some friends but then the boat wouldn't start back up. He popped the...
  9. M

    Unidentified wire

    Next question ... On the Thunderbolt 5 module and the audio alarm I do not get an alarm at key on position .. It is my understanding that the alarm is A: constant on while key is in the on position due to the oil pressure switch at the distributor (I have touched the tan/blue wire in this...
  10. M

    Unidentified wire

    This was the post that threw me off
  11. M

    Unidentified wire

    Yeah Thank you I was just reading a post about how to identify the difference between the 4 and the 5 and it was said that the 4 was mounted to the exhaust and the 5 was mounted to the distributor so I ended my search and just concluded that I had the 4 module and not the 5 but Thank you guys...
  12. M

    Unidentified wire

    Ok so it is a thunderbolt 5 ignition...
  13. M

    Unidentified wire

    There is a purple/white wire at the ignition module so I will check between the 2 wires with a volt meter.. not sure why the previous owner would have kept it in base mode but I'm sure thats why he sold it for a song because it cranks up and idles great.. he must have seen wires unhooked and...
  14. M

    Unidentified wire

    L095209
  15. M

    Unidentified wire

    I did not know that thunderbolt 5 was also on the manifold. Would the wire be at the front of the engine?
  16. M

    Unidentified wire

    Anyone have any other ideas
  17. M

    Unidentified wire

    I have the thunderbolt 4 ignition the module is mounted to the exhaust so no base mode
  18. M

    Unidentified wire

    Working with a 1998 mercruiser 4.3 I have a purple wire with a white stripe that is connected to a black wire. it comes out of the wire harness right where the fuel pump connects. My wiring diagram shows purple/white stripe wire is for trailer trim but it doesn't show that it connects to a...
  19. M

    Making engine beds

    The stringers are in but they will go untouched I am only adding the engine mounts the boat had a 3.0 in it and I'm putting a 4.3 in
  20. M

    Making engine beds

    Also do I tab first ( before I cover the a blocks) or after I cover the blocks
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