Re: 84 3.0 l4 omc sterndrive change to a new v6 engine sterndrive??
the ratios are almost identical. 1.71:1 and 1.77:1
If it is in good condition, swap away.
You'll need a new prop though. The 800 series lower gearcase has a 15 spline propshaft instead of the 13 spline size you have now.
Only other thing you might have to swap is the steering worm gear in the upper. You'll know if your steering is backwards.
But those steering pieces are easy to swap between the 2 drives if necessary.
