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  1. Scott06

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

    I would look at the rubbing block on dist to see if there is uneven wear. would try another set of points and condenser to see if that is why the dwell is so inconsistent. Have never seen a dwell bounce that much.
  2. Scott06

    4.3 GL-C - Distributor clamp bolt

    Those tamper proof Allen head wrenches or tools are available at most home stores and Amazon if u know the size
  3. Scott06

    OMC vs Volvo drives

    Modern Volvo sx drives are robust and durable. Most of what you are metioning was a hangover of issues OMC had with the introduction of the cobra outdrive. Although the drives look similar to the omc cobra Volvo heavily modified them post acquisition. Have several neighbors at the lake with VP...
  4. Scott06

    Bravo 3 loss of lube oil - slowly then rapidly x2

    You need to pull the boat before you get water in drive. When u say lower unit was replaced you you mean the lower half or the complete outdrive
  5. Scott06

    Propeller Pitch Selection

    Agreed he has to have more gear reduction. Have you tried a Rev 4 vs the enertia? The "effort to turn down low" is almost too much for my 5.0/1.81 drive. The grip on these props (incl enertia is insane)
  6. Scott06

    Fuel Pump Wiring

    Purple wire to pressure switch off the switch have a splice/T one leg to starter other leg to fuel pump. This way the fuel pump gets powered either by starter when starting or thru the Switch when ignition is on (12 v to Purple wire
  7. Scott06

    MerCruiser 4.3lx shortblock compatibility?

    I dont think the heads in as left GM condition can take anywhere close to .500” lift i think vortec may be limited to .430” with machine work
  8. Scott06

    Engine fogging

    No issue With carb at all.
  9. Scott06

    MerCruiser 4.3lx shortblock compatibility?

    Missed that. Then yes rebuild the junk yard 4.3 vortec... unless it has good compression. if so might get away with just changing head gaskets and core plugs
  10. Scott06

    MerCruiser 4.3lx shortblock compatibility?

    You can re jet your weber carb for the vortec heads. The weber carb is essentially the same as the edlebrock 1409. There are a few threads here where guys lay out the jetting needed to work on a vortec 4.3 If there is nothing wrong with your current short block take the donors heads to a shop...
  11. Scott06

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

    Ok if cooling system holds pressure head gasket is ok, look elsewhere for low compression rings or valves. Rule out dwell and timing.
  12. Scott06

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

    You said the AF side of the cooling system did not hold pressure, correct? if so there is a leak somewhere could be heat exch. Would do a poor mans leakdown test or rent a leakdown tester to see if valves are leaking by and verify dwell timing and Scott recommended. Hard to say from the...
  13. Scott06

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

    Find out if you have a valve leaking past seat that would be my inclination with low compression and backfire
  14. Scott06

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

    cyl 2 is basically dead cylinder or close to it 3 &4 are not far behind. Videos looked fine based on what you saw with pressure test I would guess head gasket. Since you could loose cooling system pressure other places besides head gasket Get #2 up to tdc with valves closed put compressed air...
  15. Scott06

    MerCruiser 4.3lx shortblock compatibility?

    Yes but you can likely prop around one or two steps in outdrive ratio like I did. What I surmised from my repower is each ratio step is approx 2" in prop pitch. This allows the boat builder to keep all different hull and power train configurations basically working within the 15"-23" 'normal'...
  16. Scott06

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

    Yes take the plugs out and ground the coil wire (take dist end off the cap) and ground. Spin it on starter. You want to look for even movement on every valve. Intakes and exhaust may have different lift amounts but all intakes and all exhaust should move about the same. The clips on the rockers...
  17. Scott06

    MerCruiser 4.3lx shortblock compatibility?

    Yes probably. I kept my V6 drive (1.81) with the 5.0 (stock except for intake and Edlebrock 1409) that should have by the factory had a 1.62 drive. I had to go up from a 19" pitch to 21" pitch. If I knew then what I know now I would have done a 5.7 instead of a 5.0. Boat was not offered with a...
  18. Scott06

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

    That temp is too high , likely you have blown a head gasket as 3.7 s are very sensitive to over heat due to open deck block design. do a compression test , if ok have you checked ignition timing? replace impeller make sure heat exch is clean. Do you have milk in oil ?
  19. Scott06

    MerCruiser 4.3lx shortblock compatibility?

    Have to agree with Scott. While a vortec head intake and carb swap will gain 20-30 hp if you have a 22 ft boat just get a 5.7. I did a 4.3 to V8 swap. Since the front and back of the 4.3/5.0/5.7 blocks are the same, you can keep a lot of your accessories and piece it together easily. Certainly...
  20. Scott06

    Fuel Pump Wiring

    https://www.justanswer.com/boat/5y7cc-wirer-electric-fuel-pump-installed.html this is a link to the merc wiring diagram shows how the OEM two terminal switch (6) is wiring into the harness and splice from starter terminal to fuel pump (7).
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