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mixing evinrude lower units 90 hp v4

1986 Newport

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Short story

I would like to run a 1995 lower unit on a 1988 90 hp Evinrude. I have read this is not possible but it seems to work during test fit. The 1995 is a 2 piece drive shaft that is slightly longer (1995 crank shafts are slight shorter). The spline outer diameter and tooth count is the same. I would understand the short shaft on the short crank might be an issue but the 1995 is the best lower unit I have.

The long story

I have a 1986 Boston Whaler with a 90 HP Evinrude. Got the boat as a free hand-me-down because of a stripped drive shaft. Bought a parts boat with a running 1988 90 HP Evinrude. I should have swapped motors and called it a day, but the mechanic I asked to do the swap convinced me all I needed to do was swap lower units and have fun on the water. Worked for a summer but the crank shaft splines let go on the way home one night. Now my good 1988 lower unit has been damaged (not as bad as the 1986). So to my wife's dismay I bought third motor, a 1995 85 hp spl. The lower unit and power head were good so I jumped on it. I plan is to run the 1995 lower unit on the 1988 engine and rebuild the 1986 with the power head off the 1995. Currently I have the 1988 engine and lower unit on the boat with the slightly damaged shaft. Plan on tuning up the engine this way but want to put the 1995 lower unit on before April so we can start skiing.

Thank you for your help,

Lee
 
Find a used OEM shaft part #5000618 or a new SIE 92-30-04-0A and pop old one out and pop new one in...

Is the part number on the shaft? I would like to buy a used one but its hard to be sure someone has a pre 1991 converted to a two piece with the right upper. Is the lower part of all the two pieces the same? I might be able to justify price of a new two piece set if I can rebuild one of my other lower units with the bottom part. ( I would have a pre and post 1991 upper to swap around)
 
Ordered new upper shaft 5000618 and a seal kit 5000411. I could have "popped" and swapped but I wanted to inspect the gears before I invested too much into it so I tore both my spare lower units down (1995 and 1986) and cleaned the components. Was not too bad of a job. Parts showed up today so I'll rebuild this weekend. I should have ordered a drive shaft retainer it did not come with the shaft or seal kit.
 
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