1978 Mercury inline 6 90hp

[Gomer50]

I am curious as to why the 90hp inline 6 was only rated at 4500-5000 RPM.All the other inline 6's seem to be well above the 5300RPM rating.Even my 80hp and 85 hp inline 4's are rated up tp 5300 RPM.Was this a Mercury brain fart??

 

[Droll]

Re: 1978 Mercury inline 6 90hp

The intake and exhaust ports on the 90 are very small, doesn't allow enough flow to allow higher rpm...

The bigger models got bigger ports and a bit higher exhaust that again will allow power at a higher rpm...


Arne Kjetil