Upper gear housing identification

[nathanglasgow]

Can anyone tell what year and Hp motor this upper gear housing is off .Its part number is cast just beside the water pump housing and is 50554-4.I bought it advertised as suitable for a 20-25hp motor but when comparing it to the one on my 1979 20hp it is too small.Is it off the earlier 20hp models or from a smaller motor entirley?Thanks

 

[Frank Acampora]

Re: Upper gear housing identification

I don't know numbers and a photo would help BUT: Earlier 20 and 25 lower units swung a 9 inch prop. Their lower unit and midleg was sized between the 9.9-15 series and the larger 35-55 series engines.

later 20 and 25s like your '79 used the same lower unit as the 35, 45, and 55. They swung a 10 3/8 inch prop on a larger prop shaft. The midleg was smaller though, and the drive shaft while the diameter of the 35-55 series was necked down to fit the smaller crankshaft splines of the 20-25.

Because of the gearing and prop, the later 20 and 25 produced more usable power and speed than the earlier ones. However, other than the top end (engine block and cowling pans), I don't think any other parts are interchangeable.

So: if the lower unit looks too small, it is too small, and is for the earlier series engines.--Sorry!

See my private message to you