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Which drive is better Merc Alpha 1 or OMC Cobra-gctid348613

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    Which drive is better Merc Alpha 1 or OMC Cobra-gctid348613

    With 2958's approaching 25 years probably looking at major rebuilds of both engines, drives and fuel tank. Been looking at several 2958's on-line, Would prefer single engine for engine / drive rebuilding & fuel economy. However the ones locally are twins & FWC:

    2 SBC Alpha 1's,

    3 SBC / Cobra

    1 5.8 Ford / Cobra

    All thing been equal which drives would be preferred and why?

    Which is more salt water tolerant?

    A second more costly but maybe better choice would be dumping the Alpha's and Cobra's and replace with rebuild Volvo DP's and bite the bullet... Brining be back to finding a single engined boat.

    Dollar wise this leads me back to finding the right 2850 CB and planning for a modern FI re-power with Volvo DP.

    Comments or suggestions please

    Rod
    Rod
    1991 4387
    Sidney, BC

    #2
    If you want a single engine, I would get a Contessa. I think the 29 Avanti tap dances on that line where it needs twins. I know if I was shopping Avantis, I would target the twin 5.8s with Cobra drives because that was the most HP offered in that hull. That means 1989 and early 1990. But, if you want a 29 Avanti with a single engine, I would target a 1990 Avanti with the 7.4L Merc Bravo setup. Swap the Bravo 1/2 for a 3, and call it a day.

    If I was doing a single engine, I would get a 1985 or 1986 Contessa with a 290/Power Trim, swap to a big block ratio DP, and yank the 5.7 and throw in a 8.1 or 8.2L big block. I know that hull will haul serious @$$ with that setup.
    Matt Train
    BOC Site Team
    Chicagoland, IL

    Comment


      #3
      Rod, The 5.0L and 5.7L SBC breathes better than the 5.0L and 5.8L Fords do. Basically, you'll get more performance from the SBC, IMO.

      I like the Fords, but cylinder head work must be done to equal that of the SBC..... again, IMO.

      As for the two drives.... Merc A and OMC Cobra:

      Both are Dog Clutch gear engagement.

      Both require a shift interrupt system of one form or another.

      Both have the sea water pumps in the drive.

      Both are Gimbal suspension.

      Both are thru prop exhaust.

      Both require a separate lower shift cable.

      Both require shift cable bellows.

      Both use a Gimbal Bearing.

      Both use a rubber hubbed drive coupler.

      Both require periodic engine drive coupler alignment.

      The Alpha max hp rating is near 300 and a max hull length of 26 foot... I believe.

      The OMC Cobra.... I'm not sure.

      Service for the Cobra can be more limited.

      Service for the A drive is very common.

      Parts are available for either drive.

      Of the two, the OMC Cobra easily lends itself to the Volvo Penta conversion which opens up the option for the Duo Prop.... if that's of any concern.

      The Ford or the Chevy in front of a Merc, Volvo Penta or OMC are going to be about the same.

      Tit-for-Tat on that.

      As for a single engine with the Duo Prop, that may be a good option if the hull is not too heavy for a single.

      .
      Rick E. Gresham, Oregon
      2850 Bounty Sedan Flybridge model
      Twin 280 HP 5.7's w/ Closed Cooling
      Volvo Penta DuoProp Drives
      Kohler 4 CZ Gen Set

      Comment


        #4
        2850Bounty wrote:


        Of the two, the OMC Cobra easily lends itself to the Volvo Penta conversion which opens up the option for the Duo Prop.... if that's of any concern.

        .
        Are you sure your not from VP sales rick ?

        The belt on my engine fell off what do I do??

        RICK : Just go ahead and pull the engine/drive, install a VP Duoprop with a brand new 8.1L fuel injected no problem all fixed up.
        :kidding

        Back to the subject, Merc Alpha 1 all the way. I have had a few with no real major issues. My 1st boat did have an omc cobra, and I did have issues with the engine side of it and since they were out of business parts were difficult to come by. An attempt by omc to do 4.3 electronic ignition had a faulty ECM and replacements were impossible to find(this particular module was only made for 1 year). I will say though, that omc did haul *** when it ran good .

        Comment


          #5
          biohazard wrote:
          The belt on my engine fell off what do I do??

          RICK : Just go ahead and pull the engine/drive, install a VP Duoprop with a brand new 8.1L fuel injected no problem all fixed up.
          Are you sure your not from VP sales rick ?
          I sure could be, Brian!

          Truth is... NO, I'm not in any way affiliated with Volvo Penta sales... although I'd not mind that at all!

          I've owned several Mercruiser and Mercury powered boats over the years, and used to work on the pre- Alpha and Alpha drives long before Merc was able to use the Cone Clutch and make the B drives. Until I began working on the Volvo Penta's, I hadn't given Volvo Penta much thought.

          But after having worked on a few of them, the light bulb came on.

          Since then I've had a preference as a result of seeing their engineering, not as a result of owning them. I own them because of this.

          That being said, all drives have their issues... both weak points and strong points. We try our best to choose wisely.

          Remember what the Grail Knight said to Indy?



          .
          Rick E. Gresham, Oregon
          2850 Bounty Sedan Flybridge model
          Twin 280 HP 5.7's w/ Closed Cooling
          Volvo Penta DuoProp Drives
          Kohler 4 CZ Gen Set

          Comment


            #6
            Thanks for the detailed replies! More questions...

            I really like the style and layout of the 2958 but the cost doing a refit with twins is prohibitive!

            Do you believe that fuel tank replacement must be figured in when purchasing boats of this age?

            Hull shape of the 2850 is more deep V than the 29/3058?

            I know of a pair of 2006, 200 hr. VP 375 hp 8.1 duo props complete with FWC, transom shields, trim pumps, alternators, pumps, gages hes asking 20000.00 for the pair... Any problem dropping one of these in 2850?

            My understanding of converting lower end of OMC drive to Duo Prop is that we still use the OMC gearbox, dog clutch and the infamous ignition shift kill box?

            Have seen Volvo Penta conversion kits advertised to covert Cobra drives to SX i think????

            If this is correct is it possible to get the VP kit as a Duo Prop?

            Have read many of your posts on the superiority of the AQ suspension... Am I correct thinking that the newer VP drives like the SX use similar suspension as OMC??

            Is the MC suspension similar as well?

            Rod
            Rod
            1991 4387
            Sidney, BC

            Comment


              #7
              Roddy wrote:
              • 1 wrote:
              • I know of a pair of 2006, 200 hr. VP 375 hp 8.1 duo props complete with FWC, transom shields, trim pumps, alternators, pumps, gages hes asking 20000.00 for the pair... Any problem dropping one of these in 2850?
              • My understanding of converting lower end of OMC drive to Duo Prop is that we still use the OMC gearbox, dog clutch
              • and the infamous ignition shift kill box?
              • Have seen Volvo Penta conversion kits advertised to covert Cobra drives to SX i think????
              • If this is correct is it possible to get the VP kit as a Duo Prop?
              • Am I correct thinking that the newer VP drives like the SX use similar suspension as OMC??
              • Is the MC suspension similar as well?



              • 1 wrote:
              • No, other than the BB being about 250# heavier than the SB.
              • No, the OMC Cobra and the Volvo Penta SX are completely different, so the entire drive is replaced with the SX or DP-S style drive.

                The gear arrangement is also completely different. Gear selection now occurs in the upper transmission unit, whereas Dog Clutch selection occurs in the lower unit.
              • No more SI or ESA, and no more split shift cables.

                The SI/ESA can all be removed and it now becomes one shift cable only from the helm to the drive.
              • The kit does either drive... SX or DP-S, since both upper units mount in the same way.
              • See above.

                Only the drive changes..... kit is same.
              • Yes, all three....., Merc, OMC and the later SX or DP-S are all gimbal suspension.

                To get away from this, you'd have to stay with the AQ series drives up to around 1996..... of which were still in production along side of the SX and DP-S until then.
              • Yes... see above.



              Rick E. Gresham, Oregon
              2850 Bounty Sedan Flybridge model
              Twin 280 HP 5.7's w/ Closed Cooling
              Volvo Penta DuoProp Drives
              Kohler 4 CZ Gen Set

              Comment


                #8
                My take is if you can't get volvo 280/290 you should get the alphas. The mercs will handle moderate performance 350s. No 383's unless you baby it, and no 454s etc.

                I ran a merc alpha, early style (there are gen 1 and gen 2). I did have some problems with it. The drive was pretty solid. There are some typical issues with a drive of this age:

                1) Steering can be sloppy. The early units had a 'splined' sttering fork which when loose, would wear out the splines. The retrofit involves taking them all apart. There is a way to do this by cutting holes in the transom plate and fitting with plugs in order to get to the steering clamp, but it's no fun. Otherwise you have to pull the engine to get to it. I did this job. You also have to remove a steering 'collar' which in my case was so seized it had to be cut out. Thankfully I had a spare.

                2) Gimbal bearings. They should last, but ANY water leaking into the bellows area, and they are toast, usually along with the ujoints. Sometimes the gimbal will just not come out. Sometimes the drive input shaft will rust into the gimbal and the drive gets stuck. What a pain!

                3) There is a 'pocket' behind the drive (In what merc calls the 'bell housing') which collects salt and corrodes out. DO maintain this area (You are suposed to check for allignment once a year anyway.

                4) Shift interrupt. This system works well, but the lower shift cables are always getting sticky, causing this system to act up.

                2,3,4 don't apply to volvos. They have their own issues though, with tilt and other steering issues. They can handle big power though, which is an advantage to those looking to repower.

                The big advantage of the mercs over volvos is power trim. It's great on a small boat, but on my big one I just want the bow down more, so I wouldn't be using it anyway.

                Chay

                Comment


                  #9
                  cfoss wrote:
                  .........

                  1..... 2,3,4 don't apply to volvos. They have their own issues though, with tilt and other steering issues. They can handle big power though, which is an advantage to those looking to repower.

                  2.... The big advantage of the mercs over volvos is power trim.
                  1... Any play or slop in the AQ series drive steering system can usually be corrected by replacing the two collar steering fork bushings.

                  This is much easier and much less expensive than correcting steering issues on a Gimbal Suspension drive.

                  2... We tend to think Bayliner ONLY here, and we aren't aware of the Volvo Penta drives after 1986.

                  Unfortunately for us, Bayliner did not use any of these drives! This is unfortunate, because these are the best stern drives that Volvo Penta put on the market.

                  .
                  Rick E. Gresham, Oregon
                  2850 Bounty Sedan Flybridge model
                  Twin 280 HP 5.7's w/ Closed Cooling
                  Volvo Penta DuoProp Drives
                  Kohler 4 CZ Gen Set

                  Comment


                    #10
                    2850Bounty wrote:
                    Both require periodic engine drive coupler alignment.
                    How about the BIII's?
                    2007 Discovery 246
                    300mpi BIII
                    Welcome island Lake Superior

                    Comment


                      #11
                      2850Bounty wrote:
                      1... Any play or slop in the AQ series drive steering system can usually be corrected by replacing the two collar steering fork bushings.

                      This is much easier and much less expensive than correcting steering issues on a Gimbal Suspension drive.

                      2... We tend to think Bayliner ONLY here, and we aren't aware of the Volvo Penta drives after 1986.

                      Unfortunately for us, Bayliner did not use any of these drives! This is unfortunate, because these are the best stern drives that Volvo Penta put on the market.

                      .
                      Holy crap, I am about to correct Rick.

                      Rick, Power Trimmed VP AQs DID make it onto Bayliners, but you need to know which Bayliners (and what years):

                      1. We already know of Mike (FordM) who had a 1984 2750 Ciera that was factory equipped with the "mumps style" Volvo power trim with a DuoProp.

                      2. 290 series Volvos with Power Trim made it on to some 1985 Contessas and a handful of 1986 Contessas, 2550 Cieras, a couple 2450 Cieras, 3250 Conquests, etc. In general, the bigger boats. Contessas were a 50/50 split, 2550 Cieras were more 25%, but in general they are not terribly hard to find.
                      Matt Train
                      BOC Site Team
                      Chicagoland, IL

                      Comment


                        #12
                        290 series Volvos with Power Trim made it on to some 1985 Contessas and a handful of 1986 Contessas, 2550 Cieras, a couple 2450 Cieras, 3250 Conquests, etc. In general, the bigger boats. Contessas were a 50/50 split, 2550 Cieras were more 25%, but in general they are not terribly hard to find.
                        My brother has a 1986 28 foot Trophy Offshore (2859 / 2860?) with a 290DP and a 454 Chevy

                        http://baylinerownersclub.org/media/....jpg[/img]
                        " WET EVER "
                        1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
                        mmsi 338108404
                        mmsi 338124956
                        "I started with nothing and still have most of it left"

                        Comment


                          #13
                          Matt, almost.... close.... but no cupy doll!

                          While I did say; "Unfortunately for us, Bayliner did not use any of these drives!" ... I'm refering to the drives after 1986 where the design became even better.

                          We all know that Bayliner may have benefitted from the 270T, the 280T (if you can call that benefitting) and the 280 PT (such as Mike Emm's) and the last few (some 85's, some 86's and even some '87's ) were fitted with the 290's, of which are also Power Trim.

                          So I'm pretty clear that most of us know this.

                          It's the good stuff after 1986/87 that we Bayliner owners don't often get to know about, unless we've owned other boat brands.

                          That's what I was refering to!

                          (Perhaps I should have worded it differently)

                          Tell ya what, Matt....... I'll give ya one today.

                          Matt.... 1

                          Rick.... 0

                          .
                          Rick E. Gresham, Oregon
                          2850 Bounty Sedan Flybridge model
                          Twin 280 HP 5.7's w/ Closed Cooling
                          Volvo Penta DuoProp Drives
                          Kohler 4 CZ Gen Set

                          Comment


                            #14
                            It's a hollow victory, sir.

                            As for the 28 Trophy, I group them all into the Contessa class since its based on a Contessa hull, but good call nonetheless.

                            - And after looking at it again, he seems to have an even more rare 1986 1/2 model.....'86 boat and drive, 1987 colors.

                            Congratulate him on having something he will likely be able to count on one hand production-wise.
                            Matt Train
                            BOC Site Team
                            Chicagoland, IL

                            Comment


                              #15
                              Thank you gentleman! Thanks for correcting my errors regarding lower VP Duo-prop on OMC upper shifting arrangement The 2958 with Cobra with Duo-prop lower adds an upgrade path for the OMC legs, if they become un-serviceable. Assume that if installing VP lower DP on the OMC upper that if the upper was to suffer a catastrophic failure, one could acquire an upper SX conversion kit and be back in business?

                              I take from non reply to the fuel tank question that these tanks are at the end of there safe service life and its when they will leak, not if they will leak

                              Was trying to be optimistic about fuel tanks but can see in cold reality that in a 2958 its a big undertaking to change tanks and this cost must be figured in...

                              Have seen numerous OMC's & MC's with what appears to be factory full FWC.

                              Don't think have seen any AQ series with full FWC. Is this correct or another error on my part?

                              Out of curiosity what improvements did VP make to the AQ series post 1986.
                              Rod
                              1991 4387
                              Sidney, BC

                              Comment

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