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What is initial timing on 4.3GL & can I advance it to improve performance?

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  • What is initial timing on 4.3GL & can I advance it to improve performance?

    If I ran super unleaded instead of 87 octane, can I set the timing more aggressively? On an EFI 5.0L Camaro I used to have, I set the initial to 10* from 0* and put super unleaded in it and no pinging or anything and it felt quicker when combined with K&N filter, and other bolt-ons etc... Would this be possible in my boat to improve performance since it is just basically a carbbed version of the same style Chevy small block motor?

  • #2
    Only if you use right oil.
    BOAT SPECS FORUM HELP STARCRAFT FORUM SHOP iboats
    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

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    • #3
      You need to get the volvo service manuals to get the timing spec.
      As for comparing your Camero engine to your boat engine... what works in a car/truck usually doesn't work as well in a marine engine. But it is your engine, so crank away with the advance, but when it grenades...

      Maybe a 4.3 is too small of an engine for your boat. Myself I wouldn't buy an 18ft with less than a 5.7. and a longer than a 22ft a 7.4
      Last edited by jimmbo; October 30th, 2018, 05:58 PM.

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      • #4
        Your 4.3 is already pushing the same power your camaro 5.0 was pushing. The Marine 4.3s are pushed to their limit

        Not much you can do. If you need more power, you need more motor
        Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

        1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

        Past Boats
        1970 Wooster Hellion - Merc 9.8
        2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
        1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

        What’s behind you doesn’t matter.Enzo Ferrari

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        • #5
          If the Camaro had one, I bet the knock sensor working with the computer kept the timing at bay.
          2002 Bryant 188 4.3MPI

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          • #6
            As the others have said, probably not going to amount to much messing with the timing. Funny thing is that the manufacturers of the engines have already figured this stuff out and set things the best possible way.

            Best regards, Ted . . . . Cape Cod, MA

            Current Boats: Formula 330 Sun Sport, O'Day Mariner Sail #3224, Sunfish
            Past Boats: Catalina 22 Sail #10531, Formula 242 Sun Sport
            Twin Mercruiser 7.4 LX MPI (0F802036, 039), Bravo 3's (0F806198, 199), Mercury 7.5 HP (1969), Johnson 4.5 HP (1980)

            My Boating Web Pages: http://www.tpenfield.com

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            • #7
              I think the 4.3s were more sensitive to detonation judging by what I see in my OMC shop manual, the V8s both can run with more total advance than the 4.3 which is more limited:

              4.3: base timing 6* BTDC, total advance at 3200 rpm = 18* (6 base + 12 mechanical)
              5.0: base timing 10* BTDC, total advance at 3200 rpm = 22* (10 base, 12 mechanical)
              5.7: base timing 8* BTDC, total advance at 3000 rpm = 29* (8 base, 21 mechanical)

              BTW the gas pumps we have at the 2 gas docks close by only sell 93 octane gas anyway, but in my shop manual it indicated if your are running lower octane gas the 4.3 should be timed at 1* BTDC.

              Before doing anything to your base timing you should use an advance timing light to check your full advance with the boat in the water so you can run it up to whatever the full advance spec is (if you can't find it use 3200-3500 rpm) boat anchored or tied up lol!
              You do not want to get into a situation where you have detonation but due to the noise inherent in running a boat you never hear it before its too late!
              What ignition do you have (Delco EST?) and is this carb or throttle body injection? Pay close attention to the color of the center electrode insulator of the plugs....you don't want it to be blistered white.....light tan or grey is good.....
              Last edited by Lou C; October 31st, 2018, 08:37 AM.
              1988 Four Winns 200 Horizon
              4.3 OMC Cobra

              98 Jeep Grand Cherokee 4.0 Selectrac
              07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

              "While air doesn't freeze....rust never sleeps"

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              • #8
                You will get more out of making sure your ignition and fuel systems are up to snuff and your prop pitch is properly selected to allow it to reach the specified max rpm at WOT, than changing the timing.
                1988 Four Winns 200 Horizon
                4.3 OMC Cobra

                98 Jeep Grand Cherokee 4.0 Selectrac
                07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

                "While air doesn't freeze....rust never sleeps"

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                • #9
                  I wish I knew how to use multi-quote so I'll respond without the quotes:

                  - I got the boat for 8500 bux from a cousin so I wans't going to shop for another '04 with a V8 (but yes of course I wish it had one).

                  - Interesting you say the 4.3 is 6* BTDC, everyone on this forum tells me 87 octane is fine (4.3GL vortec heads), but Lou seems to indicate either 87 octane isn't okay OR my boat was set to 1* from the factory?

                  - Good point on the knock sensor, the Camaro had one but I didn't feel it retard the timing or hear any pinging so I still think 10* was fine. DOES THE 4.3GL have a knock sensor? There is a sensor on the lower block with no harness attached and I thought perhaps that could be a the knock sensor and just isn't used on the carbbed short block?

                  - I cant't say the boat is under powered, I just have always liked performance so a timing advance is a cheap way to increase it a bit.

                  - Can anyone tell me if there are any special things to do to set the timing? On the Camaro I had to unhook a wire in order to set initial timing accurately.

                  - yeah Lou, the plugs looked good (platinums came on vortec motors which of course last a long time) but I am going to replace the cap & rotor and maybe the wires eventually. I'd love to do the Edelbrock 4 barrel and intake too but its money!

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                  • #10
                    Setting timing depends on your engine's ignition system. You'll need a manual. But if you tinker with the timing, fuel and power, you may have the chance to buy that larger engine.

                    A boat engine is worked much harder than an automotive engine. That is why my 4.3 only averages 3 mpg, 4 on long trips, vs. 20+ mpg if it was in an S10. Even a lead foot car driver only uses full power for a short time. Once up to speed, an auto engine barely works. With a boat, it's full time.
                    '96 Larson 174 SEI BR. 4.3LX 4 bbl Weber s/n 0F786604. Alpha One Gen II s/n 0F709315

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                    • #11
                      your motor is designed to run on 87 octane. increasing timing would increase octane requirements, however increase vacuum at idle and introduce reversion (bad)

                      your factory service manual will have the timing for your particular volvo and the ignition that is on your particular volvo 4.3

                      generally the 4.3's are on the raged edge. increasing timing, simply mean that you either burn holes in the pistons and replace the motor or you suck water in the motor, hydro-locking it and then replace the motor.

                      remember, your 4.3 is prop rated, where the camaro was crank rated. if you want more performance, get more motor.

                      Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                      1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                      Past Boats
                      1970 Wooster Hellion - Merc 9.8
                      2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                      1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                      What’s behind you doesn’t matter.Enzo Ferrari

                      Comment


                      • #12
                        Regarding your Camaro engine with the knock sensor, the computer works very fast to retard timing to where you would not hear pinging. You could probably have set it to 15 and had exact same results. The initial timing from idle until 1500rpms or so is what your butt dyno is reading.

                        For your particular 4.3, a knock sensor would only make a difference when used by an external computer controlled ignition of some sort with the port for it. Does your carbed 4.3 have TB4/5? Or just distributor controlled timing?
                        2002 Bryant 188 4.3MPI

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                        • #13
                          Not sure what TB4/5 is? I did see a GM ignition module on the distributor so it appears to be one of the newer kind.

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                          • #14
                            I think that is mercruiser terminology....Thunderbolt 4 or 5....
                            going back to the original question, the info I gave you was for OMCs specs, make sure you are using Volvo's specs for your engine...they may not be the same due to the differences between the older 1st gen 4.3 that I have vs yours which is much newer.
                            As far as what fuel octane is adequate, that is an individual thing to an extent. In that an engine might run well (ie no pinging/detonation) on 87 octane when new but as it ages and accumulates carbon build up, the octane requirement of the engine changes so it needs a higher octane gas for it to not ping or detonate. The problem is that pinging or detonation is very destructive and it is hard to hear in a marine engine. So I have always used premium gas and never had pinging or detonation. In fact even though I had two blown head gaskets at the end of the summer of '16, when I took it apart, there was no burning on the tops of the pistons, valves etc.
                            1988 Four Winns 200 Horizon
                            4.3 OMC Cobra

                            98 Jeep Grand Cherokee 4.0 Selectrac
                            07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

                            "While air doesn't freeze....rust never sleeps"

                            Comment


                            • #15
                              Sign up today
                              TB4/5 sorry, got mixed up as to which forum I was in, I will retire from this one.
                              2002 Bryant 188 4.3MPI

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