mark 20 lower unit interchange with 30?

[Chris696]

Can I put a 9 spline lower unit from a MK30 on my MK20 6 spline? Is it possable to put my drive shaft 6 spline (S) into the MK30 that has a 9 S ? Found one for sale and was suppose to be for mk20, but turns out it has 9 spline, so that's from a MK30 right? My casting broke, so I'm looking for a replacement. I've read in here that the LU of a 30 is like a 20 except for a heavier driveshaft. Is that the only difference???? Please respond ASAP so I can know to buy it or not. Thanks

 

[Chris696]

Re: mark 20 lower unit interchange with 30?

I went on mercruiserparts.com and looked at the lower unit parts for MK20 and 30. Looks like both use 1602-1439a gear housing assembly. Also the gear pinion drive shaft is 43-20805 on both. Looks like the roller bearings for the drive shafts are the same 31-28157. The shift shafts are the same too. The only difference I see is the driveshafts. Mk20 is 45-23730 and MK30 is 45-25240. Looks like I may be in luck!!! Anything I'm overlooking??? Did only the driveshafts change between 9S and 6S?? Hope so!!!!!