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Chollyfunk · 08-01-2024, 02:45

Hello all, as the title says I'm wondering if it is possible to straight swap a Penta MSB gearbox for an MS?

I have an MD11C and the MSB gearbox no longer engages forwards after a meeting with some fishing net. I'm having problems getting anyone to repair it (assume it is something to do with the gear "cone" lining?) and MSB gearboxes seem to be non-existent.

I have found an MS however and from the MS/MSB manual there seems to be little to no difference apart from the gear ratio?

Anybody got any experience of this please?

Thanks so much!

DougR · 09-01-2024, 06:05

The main difference between the models is in the shift cone and its matching gear “cups”. The MS gear used a brass cone engaging with steel gear cups....brass against steel.
The MSB used a steel cone which engaged with friction material lined gear cups. Most likely the problem which you are encountering is wear or damage to the friction material surface in the gear cup. Some owners have had success having the worn/damaged friction material replaced with new material.

Both models were available in two reduction ratios, 1:1 and 1.91:1, with the 1.91:1 being most of the production.

Other than having the reduction ratio remain the same, there is one other thing to be aware of in swapping transmissions, and that is the front gear case casting. These transmissions were used on engine models MD5,6,7,11, and 17.
Transmissions used on the 5,6,&7 had one bolt pattern in the front housing, and transmissions used on the 11 and 17 had a different bolt pattern. This has to be watched.

Chollyfunk · 09-01-2024, 06:11

Super helpful thankyou!

So as I understand the MD11C has an eccentric flange so if I find an MS with the same fitting it should be a stratight swap?

It seems having the MSB repaired will cost me the same or even more than a replacement MS or even MSB (if I could find one) as one of the tabs on the rear bell housing is broken so that would also need to be re placed - so I think it makes sense.

Would there be issues going from the 1.91:1 MSB ratio to the 1:1 MS ratio do you think?

Quote:

Originally Posted by DougR

The main difference between the models is in the shift cone and its matching gear “cups”. The MS gear used a brass cone engaging with steel gear cups....brass against steel.
The MSB used a steel cone which engaged with friction material lined gear cups. Most likely the problem which you are encountering is wear or damage to the friction material surface in the gear cup. Some owners have had success having the worn/damaged friction material replaced with new material.

Both models were available in two reduction ratios, 1:1 and 1.91:1, with the 1.91:1 being most of the production.

Other than having the reduction ratio remain the same, there is one other thing to be aware of in swapping transmissions, and that is the front gear case casting. These transmissions were used on engine models MD5,6,7,11, and 17.
Transmissions used on the 5,6,&7 had one bolt pattern in the front housing, and transmissions used on the 11 and 17 had a different bolt pattern. This has to be watched.

Engine man · 12-01-2024, 08:40

Hello - I have access to a used MS gear from a Volvo MD11C. I also have access to all parts needed to mount a Volvo MS2 gear to a Volvo MD11, or MD17.

Please contact me off list if interested. Joe

Chollyfunk · 12-01-2024, 08:52

Hey thanks so much - I think you're US based correct? I'm in the UK so maybe logistically challenging.

I'm guessing both the MS and MS2 would require new props also as they will be different ratios? How complicated is conversion to an MS2?

Quote:

Originally Posted by Engine man

Hello - I have access to a used MS gear from a Volvo MD11C. I also have access to all parts needed to mount a Volvo MS2 gear to a Volvo MD11, or MD17.

Please contact me off list if interested. Joe