I need to replace my lower unit housing and some people have told me most alpha ones were the same and some have said the opposite. I went to Mercruiser website and they do show a different part number for the R than the MR. I think I found a good deal on a used one, but I want to make sure it's the right one before I buy it. My boat is a 1986 with a 185hp 4.3 v6 . The ratio is 1.84 to 1. The serial number is 0A686991. Thanks
