Volvo MS4A repair or replace?

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Princess315

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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.
 
Princess315 said:
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.
Click to expand...
Hmm , I might have a gear set from a few boxes it have , what part of the uk are you from ?
 
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 !
 
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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.
 
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,
 
I have a spare box the correct ratio that I had as a spare for my boat that I have now parted with .
 
A not uncommon result of gearbox failure in MS4 series is the shaft punching a hole in the upper cover.
For anyone interested the generic top plate on the 270 and 280 sterndrive( possibly others ) is identical.
A quick search of the net can produce replacements for around £50-75.00 pounds.
 
Top cover is ok but I don't know how the top gear didn't escape through it! Always have paused in neutral before change of direction and annual oil changes with Mobil SHC. Prop not fouled so I suppose these things just happen sometimes.
 
So I have disassembled and inspected the gearbox further and here is a list of the damage
Upper gear in pieces, input gear teeth missing, small reduction gear damage to teeth, top bearing carrier damaged by top gear, main housing damaged through to top cover bolt threads, metal particles everywhere, all bearings contaminated.
Failure appears to be due to the centre bolt on the input gear coming loose, I experienced this many years ago on a 270 outdrive with the universal joint coming loose. Best option now appears to be another gearbox as there is not much left to repair.
Major damage all due to one little bolt!
 
Princess315 said:
So I have disassembled and inspected the gearbox further and here is a list of the damage
Upper gear in pieces, input gear teeth missing, small reduction gear damage to teeth, top bearing carrier damaged by top gear, main housing damaged through to top cover bolt threads, metal particles everywhere, all bearings contaminated.
Failure appears to be due to the centre bolt on the input gear coming loose, I experienced this many years ago on a 270 outdrive with the universal joint coming loose. Best option now appears to be another gearbox as there is not much left to repair.
Major damage all due to one little bolt!
Click to expand...

Had a look in my stock today , I have everything apart from the very bottom gear of the vertical shaft and the output shaft gear
 
Due to a ever increasing list of damaged parts I have sourced another gearbox with a known history as the easy option for now with the possibility of rebuilding what little of mine is left as a spare. Interesting everyone has advised repair rather than replace.
Superheat6k I have seen your manual and read it with interest in the past.
As the replacement gearbox is also a port side as is the failed one I would be interested if anybody would take the opportunity to swap both gearboxes to the opposite side to reverse the load and use the opposite faces of the reduction gears and use the opposite drive cone etc. Just a thought so all views are welcome, maybe ask the question as a new post.
 
Princess315 said:
Due to a ever increasing list of damaged parts I have sourced another gearbox with a known history as the easy option for now with the possibility of rebuilding what little of mine is left as a spare. Interesting everyone has advised repair rather than replace.
Superheat6k I have seen your manual and read it with interest in the past.
As the replacement gearbox is also a port side as is the failed one I would be interested if anybody would take the opportunity to swap both gearboxes to the opposite side to reverse the load and use the opposite faces of the reduction gears and use the opposite drive cone etc. Just a thought so all views are welcome, maybe ask the question as a new post.
Click to expand...

superheat6k said:
If you do decide to rebuild it this might offer some assistance as the MS4 is reasonably similar to the MS3. I wrote this when I couldn't find a manual, so and as I do this routinely for large refrigeration compressors, I thought why not for my gearbox.

Best of luck with your project ...

https://www.dropbox.com/s/2n3rlh4auna1qbz/Volvo Penta MS3B Gearbox overhaul instructions.pdf?dl=0
Click to expand...
 
Hi Paul

You appear to know more than most regarding ms4a gearboxes - is it possible you could advise me on the best way forward please.

I have removed our gearbox and noted that the axle shaft has detached itself from the gear set and the gear set threads have rounded. I have been told by numerous people that spares are difficult if not impossible to get. Is this correct or can you direct me to who can repair or supply these parts

I am currently on my way back from France with the gearbox in my car looking for the best options for my Aquastar 38 with Volvo Penta TAMD41B engines.

Any help you can give would be greatly appreciated.

Thanks

Eric
 
Sorry to hear you appear to have similar problems to my failure. I obtained a complete used gearbox and I let Paul re build it for me. Any second hand unit is a gamble and my replacement needed a selector cone as it was well worn so it had a full rebuild and should be good for a few years now. Give Paul a private message he is the person to talk to.
 
Do not dismiss repairing the gearbox. Parts are still available from Volvo Penta for this design of reverse gear, even after 40 + years.
One or two major items are no longer manufactured including the gear set,however (95% of bits )? ,including the gearshaft can still be ordered off the shelf from Sweden.
Have look at this website.
https://www.marinepartseurope.com/en/volvo-penta-explodedview-7745630-44-19577C.aspx
Some boxes such as MS4A and MS4B are virtually identical, where as the visually similar MS5 has some small internal differences in shaft bearing sizes etc.

Do not treat this as gospel but.... Princess 35 usually has the 2.63:1 ratio.(Rare as hens teeth secondhand)
Fairline Corniche/Princess 315/330 1.93 : 1 ratio.. (Bit more common " ).
Not sure about the earlier Princess 33 with 165HP Volvos. ?

Replacing just one of the boxes is not really an option.
Usual replacement path is a pair of ZF 45 (or similar) available from somebody like Lancing Marine but the engines have to be moved inch or two further back in boat to mate with shaft couplings.
If you come across a boat for sale where the engine mountings have mysteriously been relocated,its probably due to different boxes being fitted.
New box listed on ebay USA for $7000.00 dollars plus one or two secondhand units.
Anybody got any further info. ?
Hint.......... if you hear of one being sold...Buy it
 
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