1974 Merc Lower Unit Question

[country boy]

Hello,can anyone tell me if a LU housing off a 70's model 85 hp merc housing #1623-6051 fit on my 1974 115 merc ser#3945429 i found one reasonaby priced and mine needs replacement or can anyone tell me where i may be able to find the info on the web. thanks.C.B.

 

[Faztbullet]

Re: 1974 Merc Lower Unit Question

If its a empty housing it may fit if the upper bearings are the same. You will need to reshim everythng if you swap housings. If it is a complete unit you are trying to "just bolt on" the gear ratio is way off as 85 is a 2.3.1 and 115 is 2.1. Some say you can change prop to overcome difference but the one's I know that tried it have had performance problems one way or the other..

 

[country boy]

Re: 1974 Merc Lower Unit Question

If its a empty housing it may fit if the upper bearings are the same. You will need to reshim everythng if you swap housings. If it is a complete unit you are trying to "just bolt on" the gear ratio is way off as 85 is a 2.3.1 and 115 is 2.1. Some say you can change prop to overcome difference but the one's I know that tried it have had performance problems one way or the other..

yes it is an empty housing and my plan would be to swap housings someone else has one for a 115 but a little pricy and the one for the 85 hp is about 70.00 cheaper but if it wont work out without shimming or modifying the 85 hp one i think i will spend the extra and get the one for the 115.Thanks for the fast reply.C.B.

 

[Faztbullet]

Re: 1974 Merc Lower Unit Question

Anytime you swap housings you have to reshim as they are not machined the same and hp makes no difference. OMC's are different as they are machined to spec's.

 

[country boy]

Re: 1974 Merc Lower Unit Question

So it would be besides the shimming it would be ok to use the 85 hp one it looks the same from the pics ,so if its no major problem i may go with the cheaper one.Again much Thanks still learnin all this stuff.C.B.

 

[country boy]

Re: 1974 Merc Lower Unit Question

yes it is an empty housing and my plan would be to swap housings someone else has one for a 115 but a little pricy and the one for the 85 hp is about 70.00 cheaper but if it wont work out without shimming or modifying the 85 hp one i think i will spend the extra and get the one for the 115.Thanks for the fast reply.C.B.

After some negotiation i picked up this housing for the 85 H.P. for $ 95.00 shipped to me,can anyone elaborate some on the shimming of the L.U. steps to to do it.i have never done one before and i will be doing this one in the near future .Thanks C.B.