115 Lower Unit

[deanf3582]

Maube someone can help me also in this as far as merc that is . I have a 70s 115 hp tower of powe. I need a l/u for. I know the cast numbers in it are 1623 6658. Can anyone tell me what year and hp motors will cross with it. The motor has 97-102 psi on all 6 I would love to keep it and not trash it due to not being able to find a lower unit. Please any help.

 

[GA_Boater]

Welcome aboard.

Please look at the Help Tip on top of the page about posting to inactive threads. Moved your post to a new thread for maximum visibility.

Is your lower unit beyond repair?

 

[utfyrfytr]

Most of the late 60's starting I think about 67 up and through the 70's will fit. Your issue is the year of your motor. The 1970/71 motors had a drive shaft ratio of 1.78:1 the 1972-78 motors had a ratio of 2:1 (according to my manual). You need to find the year of your motor and if it is a 70 or 71 then make sure the lower unit is the also 70 or 71. If the motor is a 72-78 then you can use any the 67-70's lower units from I believe 90hp -115. I hope that is clear and not confusing you. Do some measuring of the drive shaft length and where the lower and midsection bolt together just to be sure. Good luck

 

[deanf3582]

The gear case is good. I had the one on the motor redone. I took it out and everything came out prop shaft and all. I took it back to the shop that done it and oh lucky me. They closed down. Now I know why. As far as the year I was told a 75 but no way to know 100% unless there are cast numbers on the powerhead I'm not able to see.

 

[utfyrfytr]

Find the serial # on the transom mounting bracket on your motor then you can ask here for someone to tell you what year that number indicates your motor is, that will let you know what year you need to look for or stay away from. A 1975 would mean you have the 2:1 gear ratio so that means any of the 1967 thru 70's from 90-115 hp. Just stay away from a 70 or 71 115hp as they are the 1.78:1 ratio. The only other motor to use the 1.78:1 ratio was the 70 & 71 135hp. Hope this helps.