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

ShoestringMariner

Lieutenant Commander
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Apr 18, 2015
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1,560
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

Petty Officer 1st Class
Joined
Dec 14, 2013
Messages
355
I'm not an expert, but can look stuff up, gears and prop shaft are the same part numbers.
 

ct1762@gmail.com

Senior Chief Petty Officer
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Jan 17, 2019
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761
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

Supreme Mariner
Joined
Dec 28, 2013
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The fine spline 3 cylinder driveshaft was first used in 1989 model year.
 

ShoestringMariner

Lieutenant Commander
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Apr 18, 2015
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Slightly off topic, but what are the differences between the pre 81 and post 81 lower units?

Those cases have a different PN.
 

racerone

Supreme Mariner
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Dec 28, 2013
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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 !
 

ct1762@gmail.com

Senior Chief Petty Officer
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761
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

Supreme Mariner
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Dec 28, 2013
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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.
 
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