Mercruiser 7.4L Bravo Gen V Not Starting

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by Jack Heape, Nov 30, 2021.

  1. Jack Heape

    Jack Heape New Member

    8
    Jan 14, 2021
    Little River, SC
    1997 Sea Ray 270 w/ Wesco 10k Trailer 2014 Ram 1500
    Garmin Echomap UHD 74SV
    7.4L Bravo Gen V with Bravo I outdrive
    I have a 1997 Sea Ray Sundancer 270 with a Mercruiser 7.4L Bravo Gen V engine. Bought the boat 6 months ago and engine has ran fine with no problems. Started right up every time. Yesterday I arrived at the marina and started the engine just to warm it up before we were going to go out for a short trip later in the day. Started up fine, no problems. I shut it down. 1.5 hours later went to start it up for our little day trip. Would not start. After several attempts I just let it be. Wife left for home next day so I started trouble shooting. Read several threads on the forum here. Checked the fuel filter, spinning it off emptying the fuel in a bucket to check it. No water or debris (I had just replaced the filter recently). I left the filter empty to see if fuel pump was working ok. Cranked the engine over a couple of times. Would not start. Spun the filter off and it was full of fuel, so pump is working. Put timing light on coil and have spark. I took off the air filter and held open the carb flapper to get some more air in and also sprayed in some started fluid. Engine finally cranked but ran really rough. Help carb open still and ran it up to 1200rpm. Engine really rough and a little black smoke from unburnt fuel I think. Backed it back down to idle and engine quit. My next step is I am going to replace the coil, spark plugs, and wires. Not that expensive and they wires look a little worn. Anything else I can check or look for? Looks like there is a little module on the side of the distributor cap that I think is a sensor assembly.
     
  2. jgoedd99

    jgoedd99 Active Member

    168
    Aug 10, 2008
    Buffalo, NY
    1998 370 DA
    7.4 Mag MPI Horizon Inboards
    I think a tune is probably in order as you indicate (plugs, wires, coil, cap, rotor, ignition sensors/modules, etc). Plug wires are frequently overlooked, if the plug wires are Mercruisers they will have a date code printed on them with Quarter and year, such as "Q4 1996". That is telling you they were manufactured in the fourth quarter of 1996. Can't tell you how many boats i see from this vintage still using original plug wires. My recommendation to anyone buying a 10 plus year boat is to do all your maintenance as soon as you buy it unless you have dealer records or other good proof showing it was done recently. This includes all of the above, plus filters, fluids, T-stats, impellers, fuel pump gear oil, etc. This way you know where you stand with all your maintenance, and you can follow a schedule from here on out. Doing all this preventatively is a great way of avoiding a bad day on the water.

    PS went through all this with my son's 1996 270DA with the same engine. His one lingering issue that was finally resolved this summer was to have the Weber carburetor rebuilt, these carburetors are fussy. There was dirt in the float bowl causing float to hang up and run rich.
     
    Chris-380 likes this.
  3. HawkX66

    HawkX66 Well-Known Member

    Jul 27, 2020
    SE Virginia and NH
    "Tread Knot"
    1997 Sea Ray Sundancer 290DA

    2020 F350 6.7L
    454 L29 Carb w/ Bravo III
    Not that it matters for diagnostics, but what makes you think your motor is a gen v? Should be a gen vi I believe unless it's been swapped out.
    With it running well and then out of nowhere it just won't run, then runs poorly, it screams a bad connection to me. Was the choke closed? Is that what you were holding open?
     
  4. Jack Heape

    Jack Heape New Member

    8
    Jan 14, 2021
    Little River, SC
    1997 Sea Ray 270 w/ Wesco 10k Trailer 2014 Ram 1500
    Garmin Echomap UHD 74SV
    7.4L Bravo Gen V with Bravo I outdrive
    Thanks for the input! Yes, I have already changed all the fluids, filters, impeller, fuel pump gear oil. What do you mean by t-stats? The thermostat? Didn't think of that. Will add to list.
     
  5. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Yes rebuild the carb
     
  6. Jack Heape

    Jack Heape New Member

    8
    Jan 14, 2021
    Little River, SC
    1997 Sea Ray 270 w/ Wesco 10k Trailer 2014 Ram 1500
    Garmin Echomap UHD 74SV
    7.4L Bravo Gen V with Bravo I outdrive
    I think it is a Gen V based on the Mercury Parts Catalog using the engine serial number. Its not an MPI or TBI which are the two Gen VI listed. The parts breakdown on the Gen V match what I see on the engine, for example water pump, fuel pump, ignition coil, etc.
    Yeah, I think its a bad connection as well. Now if I can just figure out what got disconnected or what wire went bad <G>. Thanks for the input!
     
    Chris-380 and HawkX66 like this.
  7. Jack Heape

    Jack Heape New Member

    8
    Jan 14, 2021
    Little River, SC
    1997 Sea Ray 270 w/ Wesco 10k Trailer 2014 Ram 1500
    Garmin Echomap UHD 74SV
    7.4L Bravo Gen V with Bravo I outdrive
    Yes, I will look at doing that. But would a carb just go from running fine to not running at all in an hours time?
     
  8. HawkX66

    HawkX66 Well-Known Member

    Jul 27, 2020
    SE Virginia and NH
    "Tread Knot"
    1997 Sea Ray Sundancer 290DA

    2020 F350 6.7L
    454 L29 Carb w/ Bravo III
    If something held the float where it wouldn't allow the needle and seat to open, yes.
    What about the choke? Did you have to manually open it? If its electronic and loses 12v when warm it will close and not allow the motor to run or run extremely bad if you can get it to start.
     
  9. Jack Heape

    Jack Heape New Member

    8
    Jan 14, 2021
    Little River, SC
    1997 Sea Ray 270 w/ Wesco 10k Trailer 2014 Ram 1500
    Garmin Echomap UHD 74SV
    7.4L Bravo Gen V with Bravo I outdrive
    Yes I was holding the choke open. It would open slightly when cranking engine. I opened it up further with starting fluid and it started, though ran really rough.
     
  10. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Start with the complete tune up as suggested. Sure if a hunk of crap gets stuck in a jet.
     
    Chris-380 likes this.
  11. HawkX66

    HawkX66 Well-Known Member

    Jul 27, 2020
    SE Virginia and NH
    "Tread Knot"
    1997 Sea Ray Sundancer 290DA

    2020 F350 6.7L
    454 L29 Carb w/ Bravo III
    I would try holding it open with a clothes pin or something. You might have fouled some plugs if it did close when it was warm.
     
  12. jgoedd99

    jgoedd99 Active Member

    168
    Aug 10, 2008
    Buffalo, NY
    1998 370 DA
    7.4 Mag MPI Horizon Inboards
    Yes Thermostat.
     
  13. Jack Heape

    Jack Heape New Member

    8
    Jan 14, 2021
    Little River, SC
    1997 Sea Ray 270 w/ Wesco 10k Trailer 2014 Ram 1500
    Garmin Echomap UHD 74SV
    7.4L Bravo Gen V with Bravo I outdrive
    Just a follow up. Bought all the stuff and went to the boat this am to start working. First off though, I checked all the wiring, wires to choke, etc.. Choke seemed a little loose. I also found one ground wire that had come completely loose that screwed onto the ignition ckt breaker mount. Fastened it back. Turned the key and she started right up. Warmed up, then let it sit for 20 minutes, cranked it again. No problems. Disconnected that ground wire and also the wires to electric choke. Still started up no problem. So I don't know what the heck it was but am going to do a full tune up anyway just to be safe.
     
    scoflaw and HawkX66 like this.

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