96 Evinrude 6hp to 8

[Dizz]

I have like new 6hp.Roughly 18 years ago since it was having issues planing off my 1236 job with 2 and load gear I wanted attempt changing to 8HP.
I went local dealer and looked in parts list and said carb is only difference.
Put it on and although it still purrs smoothly I noticed no improvement.
It does bleed black gunk from exhaust for couple weeks put up but dosen’t seem run rich.Specs call for 500 more RPM on the 8.
Dealer said just not enough arse get a 9.9.
With all parts list on internet I looked up every engine part on 6 and 8.
Ive searches everywhere I can find and I see mentioned reed valves bigger,intake bigger,etc.
Of all parts block,head,reed valves(called Leaf)intake,pistons,carb,ONLY difference is the carb and block.Why block with same reed Valves is beyond me?
Any ideas

 

[racerone]

Not everyone is well versed in parts look up.-----The 8 HP ( for many years ) had more reed petals / different intake manifold etc.

 

[Dizz]

Yes I could only find information on pre 90 motors including LeRoy
Just not much to read
It will plane off my 1443 Tracker Jon with just me and sure 17” Transom doesn’t help
Instead If building 15” And 20 transom Jon’s BassPro split the difference with 17”
Works good just little cavitation with my 15 hp right before it comes full plane