Need a Lower Unit

Hey guys,
My Frankenstein Mercury 115, in-line 6, circa 1970-80's is going to need a lower unit. I have no reverse, forward works, but goes in hard under part throttle, and every time I have checked the gear oil, it is full of metal shavings. So far it works OK, but I am sure that it won't be long before I need to replace it.
My question is, how can I determine which Lower Units from what engines/years will fit my merc. What are the different specs I need to make sure I get one that will fit.
I intend to get a good used one, slap it on, and then tear into mine and see if it can be rebuilt and keep it for a spare.

Thanks for any help or advice.

Float, Float On!

GT

PS- I don't have any good pics of it yet, but if anybody needs some, I will be posting some tomorrow...

Re: Need a Lower Unit

Any of the inline 4 and 6 lowers from 68 thru 86 will fit. There are three gear ratios. 2.33/1 2.0/1 and 1.78/1.

I like the 2.33's on everyting but the lightest of boats. (Make the torque with the gear, instead of the motor)

Your motor came standard with a 2.0 gear set.

Mercury made a 1.78 lower, why I do not know. The only motors I have seen that can take advantage of that gear are the V6's

I have a nice 2.0 early 70's lower that I can open up, inspect, reseal and sell for $250. Problem is it will cost probably half that much to ship it. (just a guess)

Try and find something local from someone you trust.

Good luck

Re: Need a Lower Unit

Thanks, that's a big help...more questions, Will the prop swap over to any of these or are there differences? Will the drive shaft and shift shaft work on any inline 6 powerheads? I mean, where there any differences in the spline counts? Does it matter if the drive shaft has a preload pin or not? And. finally, what does one of these lowers weigh without the prop? I know it will be an awkward package because of the drive shaft, but if I find one some where far, I might consider paying for the shipping and packaging costs.

Best Regards,gt.

Re: Need a Lower Unit

I have a whole 115hp on a baha, 84 model i think, very good engine just needs a pp. let me know if you want the lower because i have no title for the boat!! would cost $300 delivered.Tom

Re: Need a Lower Unit

As long as shaft lengths are same, all the lowers will interchange.

Not sure on the weight.

Re: Need a Lower Unit

Thanks again for the info, but pardon my noobness...How do I correctly measure for the shaft length?
:redface:

Re: Need a Lower Unit

I believe from where it mates to the upper,you know the flat surface to the tip of driveshaft and yeah fits alot of models.

Re: Need a Lower Unit

I wanted to thank you all for your help and let you know that I scored a cherry L/U, nearby, for a great price. I should have it installed by this weekend and test it out. Of course, I am also gonna see if the fish are biting