Lower end compatibility

[Mercnewguy]

Hello I'm hoping someone out there with a much more vast knowledge of Evinrude and Johnson motors can help me out. I am wondering if by any chance a 1975 70 hp Johnson lower end would be compatible with a 1983 Evinrude 55 hp. I haven't seen the two side by side but there is a really good deal on a lower end in my area I would love to have as a spare. Looking up the part numbers there are A LOT of part numbers that are the same. Thank in advance.

 

[emdsapmgr]

Looks like the 55 hp model in 1983 was a commercial model. If the lower unit will bolt up, it likely will present another problem. Usually the commercial model lower units have different/unusual lower unit gear ratios. These engines are made to run all day, pushing heavy barges at slow speeds. Doubtful that it would perform effectively on a pleasure boat. Simple prop changes would not make it work optimally.

 

[Faztbullet]

It wont fit as driveshaft splines a different, the 55 is a 2 cyl fine spline in a 3 cyl lower and the 70 has the coarse 4 spline shaft and gear ratio is different..

 

[racerone]

Agreed , it does not fit because of the different splines.

 

[Mercnewguy]

Thanks for the replies everyone I appreciate it.

 

[Mercnewguy]

Would it matter if it was a 1979 Evinrude 55hp and a 1975 70hp?

 

[racerone]

????----It was clearly stated that the 2 cylinder motors have a different spline on the end of the driveshaft.

 

[bob johnson]

didn't they make some 3 cylinder 55 hp outboards based on the same block as the 65 and 70 hp models?

bob

 

[racerone]

In 1968 and 1969 they made a 3 cylinder 55 hp.---And those were HYDRO-ELECTRIC shift models.

 

[Faztbullet]

In 1968 and 1969 they made a 3 cylinder 55 hp.---And those were HYDRO-ELECTRIC shift models.

and they where 4 spline also....