90hp V4 Johnson

[Firewood]

I just picked a used 90 V4 Crossflow. After some normal tuning and tinkering it now runs great. Previously I owed a 70hp Johnson. Let me say that was rated at 3gph and the 90 is rated at 11gph!! So my question is what is the difference between the 90hp and the 115hp? The displacment is the same, I did my best to cross reference parts between the motors but everything seems to match and be interchangeable.? SO wheres the extra 25hp come from? The way I look at is if i'm burning 11gph I might as well get an extra 25 ponies. The only thing I can figure is the timing is different or intake is different. Also I did see a reccomendation to set timingto 24degrees instead of 28 at WOT.

 

[Firewood]

Re: 90hp V4 Johnson

^bump^

 

[Big Rod]

Re: 90hp V4 Johnson

Firewood, Hi, I'am pretty sure it's the ability to flow the fuel/air mix in and the exhaust gases out quicker.On the 115's and 140's, you will notice a bump on the exhaust side that is not present on the 90's. That bump houses exhaust headers like a race car engine.The cylinder exhaust ports are larger and fitted with smooth flow inserts.Larger bore carbs.,timing etc. all leads to a hopped up 90 and boy did those modifications work. Hope this helped...

 

[Firewood]

Re: 90hp V4 Johnson

I figure this winter I'll change the reeds and see what I can do to help it breath a little better. Always can use more power!