difference between 1980's Evinrude/Johnson 4.5, 6, 7.5, 8 HP

[merc20076]

I have a 1981 Evinrude 4.5HP lower unit in good condition since the powerhead has no more good compression. In fact I wanted to re-build it but both pistons were different and rings for the 2nd are NLA. I've heard that they are the same as the 7.5HP models is this true or not? Is 6 and 8HP the same also?

If I can find a good working 7.5 HP motor that as a busted LU I'd install it on my LU in good condition. I am planning to buy a inflatable SIB so I could work to save alot on a outboard.

 

[steelespike]

Re: difference between 1980's Evinrude/Johnson 4.5, 6, 7.5, 8 HP

Beginning in 84 the 6,7.5 and 8 hp arec all 10cu in.69-79 6 hp is 8.84 probably somewhat related to the old 5.5.and has the old style split gearcase.It appears the 2.5,3 and 4.5 are all 5.28 cu in.It does appear the 4.5,later 6,7.5 and 8 hp share
a gearcase can't speak for the mid leg.

 

[Chinewalker]

Re: difference between 1980's Evinrude/Johnson 4.5, 6, 7.5, 8 HP

The gear cases are the same across the line, except for the waterpump housings, which use different grommets on the 4/4.5 models. Mid-legs are different between the 4/4.5 and 6-8 models.

 

[merc20076]

Re: difference between 1980's Evinrude/Johnson 4.5, 6, 7.5, 8 HP

Searching for 1981 4,5HP parts, the 7.5HP is in the same list.


http://www.boats.net/parts/search/BRP/EVINRUDE/1981/E5RHCIC 1981/parts.html

Can a 7.5HP bloc can fit on the rest of a 4,5HP mid and lower unit?

 

[Chinewalker]

Re: difference between 1980's Evinrude/Johnson 4.5, 6, 7.5, 8 HP

No - bolt patterns are completely different. You would need a 6/7.5/8 mid...