Interchangeable Lower Unit help..........

[tswheezer]

I have a 90hp Mercury Tower of Power. Runs great but I have a feeling the lower unit is going to be going soon. Can anyone please tell me which years are interchangeable with this lower unit I have so that I can start looking just in case.
Want to get the family out there boating soon.
Thanks!

 

[tswheezer]

Re: Interchangeable Lower Unit help..........

Anyone???? I really could use the help. I need to order something so that we can get out there on the water soon and have no clue.

I have a 90hp Mercury Tower of Power. Runs great but I have a feeling the lower unit is going to be going soon. Can anyone please tell me which years are interchangeable with this lower unit I have so that I can start looking just in case.
Want to get the family out there boating soon.
Thanks!

 

[Wingedwheel]

Re: Interchangeable Lower Unit help..........

What is the year and ser # of your motor?

 

[hotrod53]

Re: Interchangeable Lower Unit help..........

When I recently replaced mine on my Merc 500 I needed to know shaft length, number of splines, does it have a preload pin, and what size and year your motor is. Start by looking up on top of the lower unit near the water pump, there will be a casting number that will help you match it up. You may find that a suitable replacement will not necessarily have the same casting number.

There are many sources for used replacements, Ebay is one. Many of these guys are recyclers and can help match it up for you. I would suggest asking if it were pressure tested, that insures that the seals are good.

 

[Mi duckdown]

Re: Interchangeable Lower Unit help..........

Why Do you think that the lower end is going soon?

 

[tswheezer]

Re: Interchangeable Lower Unit help..........

The motor is a 1978 Mercury Tower of PowerLong Shaft - Serial number is 4848289

 

[Chris1956]

Re: Interchangeable Lower Unit help..........

gearcases from early 70s to late 80s, from inline 4 and 6 motors are interchangeable. IL4s can have different gear ratios. Most all are longshaft.