Can anyone let me know the major differences between a #4 and a #5 mercury drive. Can a 5 bolt right on to a #4 extention box. Horsepower ratings? reliability? Parts? Height difference. Any help would be appreciated. Thanks NK

The 4 & 5 share the same bolt pattern and I believe same length. They both have virtually no cavitation plates and do cause extended time getting on plane! In fact some folks gave up because of great difficulty gettting on plane and assosiated drivability issues( going up wind or down w/ bow high and loss of visibility, while feathering throttles etc. etc.) They are about 5 " -7 shorter than #3 a or #3's. However the #5 is much stronger and will handle more Tq. the #5's DO eat up horsepower!! Dave

The first built V's were not a whole bunch different thean the IV's and they also had the IV's polygon shaft and gear sets. The later V's have net forged gears which I hear are stronger. I ran IV's with 800 hp going to them with no real issues. I switched over to V's with net forged gears this season. Had it out once. Didn't notice any real performance difference. The gear case in the V is close to an inch shorter than a IV as well. If you are looking for IV's I have a pair fresh from TNT with 1.33 gears.