9.9 powerhead on a 7.5 chassis?

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samleen18

Cadet
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Apr 23, 2025
Messages
15
I recently got my hands on a johnson 9.9 powerhead from the late 1980s. my current outboard is a 1982 evinrude 7.5. the bolt pattern on both motors is the same, so I am wondering if I can fit the 9.9 powerhead to the 7.5 chassis to get a boost in power without adding a lot of weight.

the boat is an avon rover r2.80 that the 7.5 struggles to get on plane
 
jimmbo

jimmbo

Supreme Mariner
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May 24, 2004
Messages
13,674
Welcome to iboats
I doubt the 7.5 Gearcase is robust enough to handle extra Torque of the 9.9, and Propping could become an issue
 
S

samleen18

Cadet
Joined
Apr 23, 2025
Messages
15
jimmbo said:
Welcome to iboats
I doubt the 7.5 Gearcase is robust enough to handle extra Torque of the 9.9, and Propping could become an issue
Click to expand...
evinrude did make a super10 that I read was the 9.9 powerhead on the 7.5 chassis. I couldn't find much more info on it
 
R

racerone

Supreme Mariner
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Dec 28, 2013
Messages
38,499
???----Not sure how you determined that a 9.9 HP will fit on the 7.5 HP midsection ----Because it will not fit !!-----And the " super 10 " was not a 9.9 on a 7.5 midsection.-----Sorry --you are sadly mistaken on these 2 topics.
 
kbait

kbait

Commander
Joined
Nov 13, 2007
Messages
2,471
Agree w/racer^.. powerhead base gasket 9.9 vs 7.5
 

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