Re: Will a 1988 125HP lower unit work on a 1989 125hp
You can use lowers from either an 85 or 125 within the years of 1984 to 1991I believe. Frank A. can correct me if I am wrong. There is a gear ratio difference between the 85 and 125 but, if necessary, you can work around this with a prop pitch change.
There are usually lowers for sale on ebay motors and craigslist.
Re: Will a 1988 125HP lower unit work on a 1989 125hp
Iknow for sure a 85hp, lower unit will work, I did a power head swap from a 1987, 85 hp and put a 1989, 125 hp power head on the lower unit, bolts up just fine,and runs great
Re: Will a 1988 125HP lower unit work on a 1989 125hp
Any 3 or 4 cylinder lower unit from about 1979 to 1990 with the possible exception of the later Force 70 horsepower will fit. Bolt pattern, shaft size and length were the same. Water pump was slightly different but will mate up perfectly. The only thing you need to be careful about is shaft length. Some engines were 20 inch long shaft and some were 25 inch extra long shaft. Obviously, if you have a 20 inch and buy a 25 inch lower, you will need to change the shaft and vice-versa.
Your 125 had a gear ratio of about 1.78 to 1. Some 85s and all 90s had a 2 to 1 ratio. If you get one of those, you will need to go up two pitches in prop to keep RPM the same. However, you should be pleasantly surprised because you will most likely see a 3-5 MPH increase with a 2 to 1 lower unit ratio and the larger prop.
