75hp Chrysler lower unit swap?

[Tnstratofam]

We purchased our second boat last Thursday. It is a beautiful 1982 Starcraft 16 footer with a 75hp Chrysler outboard. The lower unit is shot. Had a mechanic tell me that Force lower units would work. He said the 85hp and 125hp wouldn't but others ,70hp, 75hp, 90hp, 105hp would bolt right up. The powerhead on the engine is good. New carbs and good compression. My question is should I try to repair the engine or look for something else to replace it with. I plan on upgrading the engine in a couple of years with a complete restore. The boat is lake ready otherwise and in excellent shape. The PO put in a new floor and seats before he realized the lower unit was bad. We want to get her back on the water for some fall and winter fishing so the lower unit will be the quickest with our budget, but I don't want to waste our money on that if I would be better off just replacing the engine and controls. I'm going to verify the engine is in running order before I spend anything on her. The admiral wants this boat running so I can start our restore on our ski boat. Any opinions will be appreciated. Thanks to all.

 

[jerryjerry05]

Re: 75hp Chrysler lower unit swap?

The direct swap would be 75-79 75hp.
The newer 85/125 might not work?
Get pics.
Start your motor search early.
If you change brands, OMC/Mercury/yam will need controls and wiring harnesses.

 

[Frank Acampora]

Re: 75hp Chrysler lower unit swap?



If the engine is a 1982 also, and if it indeed does have the one piece lower unit, ANY lower unit from 1979 up to 1990 will bolt up. HOWEVER, gear ratios were different and performance may suffer a bit if the incorrect ratio lower unit is installed. IF you do use a later lower unit, it may also be necessary to cut a clearance slot in an internal web inside the bottom of the midleg.

Here are a couple of different lower units. Later units with two piece drive shafts will fit but the water pump is larger and you will need to grind a little clearance in the midleg.

Last photo shows a 1990s dual exhaust lower unit mounted onto an early 1980s Chrysler 105. So, if you are willing to do a little extra work, many lower units will fit.

 

[Tnstratofam]

Re: 75hp Chrysler lower unit swap?

Thanks to all for all the info on the swap. We got lucky ( I Think ) A local marina had a good used 75hp Chrysler lower unit that we pressure tested and changed the oil in. They gave me a 30 day warranty. We took it out this past weekend and The motor performed well. Also thanks Frank for your help in setting my timing and carbs up through your posts. That helped a bunch. Happy boating to all. Until our next repair. Thanks again Dave.