3a versus no.6s
 

Hi
We have ssm3a drives(with uprated internals good for 800hp apparently). Changing engines to about 850-900hp. We'd like to stick with the 3a drives. The boat is used in very rough seas in the U.K.
No.6s have been suggested as necessary, what do you all think?
Thanks Jonathan

3A are good drives, so are all speedmasters IV, V, and VI. If your going to make a change the #6 is a great choice and will handle the power better, but they are heavier, expensive, and quite a bit of work to convert. It would be less expensive to buy a spare set of 3A drives and freshen both sets a couple times before redoing your transom and rigging to install a pair of sixes.

Many thanks for the reply.
Forgive the lack of knowledge but I had assumed they all used the same transom parts and so an easy job. So, in fact they are completely different and the whole transom will need re-doing, shape of hole etc etc. Is the no6 the big daddy with nothing above apart from Arnesons?

You also have the M8, similar to the #6 but Mercury's newest big power drive

Thread on conversion from SSM5's to 6's. BTW, SSM5's are a shortened 3A. http://www.offshoreonly.com/forums/c...comes-six.html

Many thanks Griff, great thread. Lot of work in that conversion!! I think for now we'll stick with the 3as and see how we get on, the main reason being cost(anyone got cheap no6s?)
All the best

One further question please..... what is the weak point of the 3a? Which part/shaft/bearing fails first?
Thanks Jonathan

If you are boating in very rough seas like you say a wise investment would probably be a set of Drive Guardians to help prolong the life of those 3A's.

^^^ agree.
Not only safe guards the drives but transmissions too.


http://33outlaw.zenfolio.com/img/s9/...09397899-3.jpg

Mine are set up to slip anything above 900ft/tq



http://www.marinedesigncorp.com/2014.html

and the crankshafts