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  1. #1
    Join Date
    Oct 2018
    Posts
    10

    Default Volvo MS4A repair or replace?

    Hello, after 12 years of trouble free service one of my Volvo Penta MS4A gearboxes on an AD41 has suffered major failure and all advice and opinions and next steps are welcomed.
    After removal and disassembly of the gearbox the cause of failure appears to be the bolt on the input shaft gear has come loose. The result is the top gear is now in two pieces and the input gear has teeth damage so gear set is a write off.
    The reduction gears appear ok along with the oil cooler.
    All bearings contaminated with metal pieces.
    The flywheel damper plate appears ok.
    I know gear sets are out of production so one option is to find another 1.95 ratio box and refurbish before fitting although final costs may be close to an alternative gearbox.
    A better option is replacement of both with ZF45A or 63A or similar and sell the other good gearbox to recover some costs. We intend to keep the boat for many more years so I do not mind the expense of new gearboxes.
    Has anybody had experience of replacing the gearboxes with ZF or similar and can offer any advice? I will be doing the work myself so any advice is welcome. Reduction ratios are also slightly different with the alternatives and current WOT revs are about 3900 at 25 knots so will a re pitch of propellers be necessary? ZF units are shorter, has anybody used extension sections on prop shafts to avoid moving engines backwards? Prop shaft behind the coupling is also very short before the gland packing. Lifting engines with spacers under the feet is not a problem. Clearance under the MS4A is tight so any increase in size in the bottom of the gearbox could be an issue.
    Thankfully the failure happened on the return journey after our holiday and we were able to return back to our berth on one engine although the replacement option will now be a winter project possibly with posts of progress on here.
    I am new to the forum so please give me time to get the hang of things with replying etc.

  2. #2
    Join Date
    Apr 2007
    Location
    midlands
    Posts
    7,298

    Default Re: Volvo MS4A repair or replace?

    Quote Originally Posted by Princess315 View Post
    Hello, after 12 years of trouble free service one of my Volvo Penta MS4A gearboxes on an AD41 has suffered major failure and all advice and opinions and next steps are welcomed.
    After removal and disassembly of the gearbox the cause of failure appears to be the bolt on the input shaft gear has come loose. The result is the top gear is now in two pieces and the input gear has teeth damage so gear set is a write off.
    The reduction gears appear ok along with the oil cooler.
    All bearings contaminated with metal pieces.
    The flywheel damper plate appears ok.
    I know gear sets are out of production so one option is to find another 1.95 ratio box and refurbish before fitting although final costs may be close to an alternative gearbox.
    A better option is replacement of both with ZF45A or 63A or similar and sell the other good gearbox to recover some costs. We intend to keep the boat for many more years so I do not mind the expense of new gearboxes.
    Has anybody had experience of replacing the gearboxes with ZF or similar and can offer any advice? I will be doing the work myself so any advice is welcome. Reduction ratios are also slightly different with the alternatives and current WOT revs are about 3900 at 25 knots so will a re pitch of propellers be necessary? ZF units are shorter, has anybody used extension sections on prop shafts to avoid moving engines backwards? Prop shaft behind the coupling is also very short before the gland packing. Lifting engines with spacers under the feet is not a problem. Clearance under the MS4A is tight so any increase in size in the bottom of the gearbox could be an issue.
    Thankfully the failure happened on the return journey after our holiday and we were able to return back to our berth on one engine although the replacement option will now be a winter project possibly with posts of progress on here.
    I am new to the forum so please give me time to get the hang of things with replying etc.
    Hmm , I might have a gear set from a few boxes it have , what part of the uk are you from ?

  3. #3
    Join Date
    Nov 2001
    Location
    scotland
    Posts
    3,416

    Default Re: Volvo MS4A repair or replace?

    Quote Originally Posted by volvopaul View Post
    Hmm , I might have a gear set from a few boxes it have , what part of the uk are you from ?
    Volvopaul is acknowledged as one of the resident experts on here (no connection etc) so worth speaking with

  4. #4
    Join Date
    Sep 2011
    Posts
    2,228

    Default Re: Volvo MS4A repair or replace?

    Quote Originally Posted by scottie View Post
    Volvopaul is acknowledged as one of the resident experts on here (no connection etc) so worth speaking with
    +1, One of the most respected and helpful mechanics on the forum, also no connection.

  5. #5
    Join Date
    Nov 2001
    Location
    Medway
    Posts
    19,875

    Default Re: Volvo MS4A repair or replace?

    Go for repair if you can with any secondhand parts available, inexpensive and fast course of action to go down plus the benefit of the boat not having to come out of the water.(unless you have those PITA deep sea seals). All other bits needed to reassemble (gaskets/seals etc) are available, most on stock.

    The alternative is to change one or both of the reverse gearboxes, which usually means you have to physically move and reposition the engines, then realign shafts. Plus sort the oil/water cooling pipework and very probably repitch props.
    Gaskets/shims/ seals/bearings for my rebuild came from Keyparts, cost around £150.00.
    Have not heard of anybody drawing shafts backwards or using some sort of extention to mate shaft with new gearbox.
    VolvoPaul will be your man on this case.
    Many of the major parts that do fail in this reverse gear are still available from Volvo.
    It is a common misconception that any failure in this box is the end, it is not so.
    Two boxes in our club which had major component failure recently, simply repaired and quickly put back into service.
    Something else to consider, these boxes are now nearly 40 years old and there must be thousands and thousands out there suffering both neglect and abuse.
    So a few give up !
    Last edited by oldgit; 18-07-19 at 07:34.

  6. #6
    Join Date
    Oct 2018
    Posts
    10

    Default Re: Volvo MS4A repair or replace?

    Thanks for all the advice so far. Of course repair is the simple option I suppose I might have lost some faith in the gearboxes but they have given years of reliable service. Volvopaul the boat is located at Newark and the gearbox is removed and at home. If you have spares I am interested, just let me know. If you have I will examine the reduction gears for damage. Also there is damage to the inside of the case around where the top gear exploded but this is just appears cosmetic in the rough cast area.

  7. #7
    Join Date
    Apr 2007
    Location
    midlands
    Posts
    7,298

    Default Re: Volvo MS4A repair or replace?

    I am sure I have a complete top gear set , vertical shaft and cone , plus a casing , front housing , lower housing etc .

    If your final drive is ok there is no reason your box can’t be rebuilt, send me a private message with your details,

  8. #8
    Join Date
    Oct 2018
    Posts
    10

    Default Re: Volvo MS4A repair or replace?

    Thanks to all for advice and opinions so far. Differing views and approaches are all welcome.

  9. #9
    Join Date
    May 2015
    Posts
    73

    Default Re: Volvo MS4A repair or replace?

    I have a spare box the correct ratio that I had as a spare for my boat that I have now parted with .

  10. #10
    Join Date
    Oct 2018
    Posts
    10

    Default Re: Volvo MS4A repair or replace?

    Hello Amour, what condition is the box in? Is it as is or has it been refurbished? What area are you in?

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