Re: 1974 75HP Chrysler Lower unit leaking around the 2 piece split!!
Depending upon the age of the lower unit it will either be a 2 bolt or 3 bolt gearcase. Using the three bolt as an example: there are three long studs running from the gearcase to the top of the midunit: One at the point and two behind the water pump. The front one runs through a hole in the point of the leg with a 3/8 nut and washer on top. the rear two run through the oil chamber and in addition to the nut the one nearest the water pump has a sealing O-ring and a heavy washer.
Remove all three nuts and washers and the gearcase should (with a little tapping) come down. The gearcase has a milled groove and large O-ring to seal it. It also has a locating bushing and sealing O-ring at the front stud.
Clean everything well and coat with non-hardening Permatex or silicone RTV and reassemble. If the gearcase appears corroded at the sealing surfaces do NOT sand down to clean metal. The relation of gearcase to midleg sets the pinion gear lash. Changing this dimension will grind off the gear teeth in some period of time depending upon how much metal was removed.
Until you get the other gearcase assembled, clean well then coat the crack between the gearcase and midunit with Permatex. Very temporary stopgap, not to be considered permanent.
2 to 1 ratio should have given a 3-5 MPH (perhaps if lucky, even as much as 8 MPH) increase in top speed.
Later, if you get flush with cash or really ambitious, set the powerhead on a 1979 or later one piece midleg and lower. You can use all your cowls and hardware but the one piece has better prop selection and will give 1-3 MPH more than the 2 piece.
