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  1. Scott Danforth

    1986 Mercruiser 470/170hp/3.7L Carb backfire, low vacuum, other weird issues

    I would drain the coolant prior to the leakdown test. I would also re-test the water jacket
  2. Scott Danforth

    MerCruiser 4.3lx shortblock compatibility?

    The PO states in post #1, his block is toast.
  3. Scott Danforth

    1986 Mercruiser 470/170hp/3.7L Carb backfire, low vacuum, other weird issues

    Here is a picture of the open deck. see how any combustion gasses seeping past the cylinders except that little bit of landing in the middle would have to go into the cooling water jacket. here is a picture of the open deck being closed for a high-performance hot-rod build.
  4. Scott Danforth

    1986 Mercruiser 470/170hp/3.7L Carb backfire, low vacuum, other weird issues

    the pressure test says that your head gasket where the cooling passages are is in tact. being an open deck block, it would be unlikely for combustion to transfer from one cylinder to another without entering the combustion side. you did have the cooling water drained when you did your test...
  5. Scott Danforth

    I freeze my block so you don't have to!

    wait until ambient air in the garage falls to 20 and you will see your block temp drop quicker. right now your still at 25ish with an 37 degree block. you have a thermal mass of iron in the 400# range. knowing that ductile iron has a k factor of about 70, you should be able to calculate the...
  6. Scott Danforth

    Increase power 1993 150 proV

    Time to understand how a carb works, Bernoulli's principle, and what a carb signal is.
  7. Scott Danforth

    1986 Mercruiser 470/170hp/3.7L Carb backfire, low vacuum, other weird issues

    When setting points, going to quote my father and high school autos teacher..... feeler gauge is close, setting with a dwell meter is accurate
  8. Scott Danforth

    Increase power 1993 150 proV

    swapping to bigger carbs means the signal other than WOT is lost and drivability from idle to mid-range suffers.
  9. Scott Danforth

    Swapping engines 2004 90hp mercury to a 1989 125 Force wiring

    why step 15 years backwards to an obsolete motor?
  10. Scott Danforth

    MerCruiser 4.3lx shortblock compatibility?

    FWIW, I start a big block without a choke and dont have start issues or idle issues. throttle to 1/3 for the first 30 seconds or so for it to clear its throat. then as I deal with lines, etc, the motor warms up to about 120, and I am off I used to runt a 360 mopar without a choke in wisconsin...
  11. Scott Danforth

    MerCruiser 4.3lx shortblock compatibility?

    then you didnt tune the carb right
  12. Scott Danforth

    Boat wont start

    Pull plugs and try to turn it over. if water comes out, you have trouble shooting steps ahead.
  13. Scott Danforth

    1986 Mercruiser 470/170hp/3.7L Carb backfire, low vacuum, other weird issues

    I would look at timing. if you havent set dwell with a meter, start there
  14. Scott Danforth

    MerCruiser 4.3lx shortblock compatibility?

    You can get low mileage running 4.3 motors for under $200
  15. Scott Danforth

    MerCruiser 4.3lx shortblock compatibility?

    I would avoid EFI in a boat for many reasons. You have to use Marine EFI (very expensive), and it doesn't make more power or better economy If you use an aluminum motor, you need to run a heat exchanger
  16. Scott Danforth

    Random

    You met my Uncle's?
  17. Scott Danforth

    1986 Mercruiser 470/170hp/3.7L Carb backfire, low vacuum, other weird issues

    Use a factory head gasket Measure the head for flatness with a machinist ground bar. If it isn't flat, get it machined If you shave your head, you need to remeasure your push rods
  18. Scott Danforth

    1986 Mercruiser 470/170hp/3.7L Carb backfire, low vacuum, other weird issues

    you ran it to 200F. you already spit the head gasket. they spit their head gasket if the temp goes much over 175 best you can do is do a compression test and hope you didnt score the pistons. BTW, these motors have high cranking compression. you should see 170PSI on the gauge. if you lost...
  19. Scott Danforth

    MerCruiser 4.3lx shortblock compatibility?

    The OP's 22' islander sure could use a 5.0 or 5.7
  20. Scott Danforth

    . . . and I Thought Hi-tech Boat Engines Were Bad . . .

    Im on the 3rd rebuild of a trans because the factory GM (JMBX) torque converters are a joke. only 0.5mm of carbon fiber clutch face bonded and pressed by a hydro-formed piston. they edge load, eat the friction material, take out the pump, which in turn drops pressure and the trans eats itself
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