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  1. 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...
  2. 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'...
  3. 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...
  4. 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...
  5. 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 ?
  6. 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...
  7. 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).
  8. Scott06

    Fuel Pump Wiring

    You need to add a new switch that is the oil gauge sender with one wire on it. If you look at parts 41,42,43 in this diagram they use a 1/8" npt T to put the sender (41) and oil pressure switch (42) into the oil system. You can reuse your sender and get a 1/8" T and pipe nipples to attach...
  9. Scott06

    Working During Winter

    Why not just pull the drain plugs after every time you use it? In mine this takes 10 min... You could do a tub if it were big enough and you had the refractometer to check and top up AF strength. Would need a huge tub I think the marinas that winterize this way use a couple 100 gallons of PG...
  10. Scott06

    Dieseling after shut off and loud noise when trim is higher in shallow water

    Agreed trim it back down a hair and the rattling should stop
  11. Scott06

    Dieseling after shut off and loud noise when trim is higher in shallow water

    Our dock is in shallow water (27") so every time I go in or out we are at max up on the trailer button. Important to keep rpms at a min doing this Would pull your drive check gimbal bearing, U joints, and engine alignment. Check bellows for cracking or splits. Also a good time to do the water...
  12. Scott06

    Mercruiser overheating

    Take the elbow off and see if the passages are clear. I think you may also be able to take a cap off each end of yours. As along as water can flow it is ok
  13. Scott06

    Mercruiser overheating

    In freshwater they outlast the boat. Have had boats 40+ years old with original exhaust manfiolds in perfect working condition
  14. Scott06

    Mercruiser overheating

    I would bet the passages in your thermostat housing are plugged. The one "after the thermostat" -I assume you mean the hose that feeds water to manifold? that should be flowing some water at all times to cool the exhaust even when the thermostat is not open. Or do you have a separate feed to...
  15. Scott06

    Propeller Pitch Selection

    What is the drive ratio? I think with a boat that light will need a 1.47 drive and probably a 21" pitch or maybe a tad more pitch. As outlined you want to find a prop shop like Hills or I think Prop MD does pitch exchange. Just need to find someone who will work with you to try before you buy...
  16. Scott06

    Trim pump wiring acting opposite

    I think the 4 th one is for trailer button you have two up buttons trim and trailer trim works through the limit switch trailer always works regardless of drive position
  17. Scott06

    Need RPM’s on 383MPI 1970 SeaRay 24’ project

    When reading plugs they show what you last ran which was likely idle to read them you need to run at what ever rpm you want to look at afr then cut it off immediately and pull a plug
  18. Scott06

    4.3 Mercruiser Crank, No Start

    You will not get any power to fuel pump if engine is not running and ignition is on unless you jump out the oil pressure switch. The purple yellow from starter is what supplies power during cranking. If you think is fuel related dump some gas down carb and crank it over.if you have ignition it...
  19. Scott06

    Winterization

    If you got full amount of water out of the 5 drain plugs then you are good I would drain the -50 af you put in and leave it dry given the temps u state If you ask two guys on here about af or no af you will get 3 different answers … I personally don’t use it and have never had any corrosion...
  20. Scott06

    Mercruiser Vacuum Gauge

    Would Anni correct pitch show lower or higher vacuum
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