interchangeable lower units

will the lower unit from a 89 model serial # C162231 ELPTO mercury interchange with a 96 serial # G317774 ELPTO MERCURY BOTH ARE 90 HP

They are not the same part number and the latter model had two different clutches - so can't give you anything more than a "maybe".

In mid 1994 Merc made "some changes" to the majority of their model line. Many things stayed the same but enough changed that some items were no longer a "bolt on" replacement.

Both units used the same drive shaft, so that will "fit in" to the crank and I would assume that the bolt pattern will be the same, but I wouldn't want you relying on my word and having an item shipped at significant cost only to find that it is a touch different.

In late 1993 the reverse gear was changed from a 3 dog to a 6 dog and the change also resulted in a longer internal shift throw. The 89 unit will bolt up but you would need to swap to a 1989 shift linkage to make it operate. The 89 linkage is a 8-1/2" overall and the 90 and up are 8-1/4"... Cheapest way is to order a SEI unit..

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I have a bad lower unit on a 8hp 2-stroke mercury. I was also wondering if I can swap it for an earlier merc 8hp 2-stroke.

The one that's bad is a 1995 serial# 0G235566 model# 1008211RD

The one I want to swap in is a 1991 serial#0D008423 model#1008201LD

Thanks for any help you can provide.

George