60 & 70 hp gearcase 88 and 89 differences beside driveshaft?

[ShoestringMariner]

Hey guys, I’m pretty sure 1988 was last year of the 4 spline shaft, but is that the only change?

Will a 1981-1988 gearcase work with 1989 internals?

Thanks in advance

 

[juno pierrat]

I'm not an expert, but can look stuff up, gears and prop shaft are the same part numbers.

 

[ct1762@gmail.com]

i literally just got done putting a rebuilt 1985 70hp on a 1979 75hp midsection and lower. they bolted up perfectly. i also think the 89' was a 4 spline as i've put a 49 cube powerhead on a 1989 midsection with the only change required was the adapter, and went to a fine spline around 92' or 93' when they changed to oval port goodness. but then again don't have both in front of me.

 

[racerone]

The fine spline 3 cylinder driveshaft was first used in 1989 model year.

 

[ShoestringMariner]

Slightly off topic, but what are the differences between the pre 81 and post 81 lower units?

Those cases have a different PN.

 

[racerone]

Different shape nose.-----Different bearing housing on front of the propshaft !!-----The bearing housing was made smaller as the nose of the gearcase is different !

 

[racerone]

Shoestring-----Your location ?

 

[ct1762@gmail.com]

Racer i've got a bunch of 3 cyl loopers. the 89' that accepted my older 49ci block was a 4 spline i'm positive, but is it possible my 89' was an early production run that still used the 4 spline from previous years (86-88 56ci)? must be! ill be taking apart yet another 89' 56ci motor and will pay attention to the splines. I've got a 1980 75hp 20'', a 1981 and 1982 both 70hp. would any of those be considered "small gearcase" ones? ill take a look at the bullets on the gearcases and see if i can spot the difference. I assume the 75hp one would be the best for top end correct?

 

[racerone]

It takes a long time to learn what fits what I guess.----When motors are 30 years old there is always the chance that parts have been swapped over.