I have a '94 Larson 19.5' boat with a Volvo 5.0FL and a SX outdrive. One of the things I noticed with this outdrive is there is no trim tab, just a plug where the trim tab goes. Is this normal, or should there be a tab. I downloaded the manual, and it shows the tab and the installation procedures. So, are all outdrives supposed to have a trim tab, or do some lack them? And why would one outdrive have them, and another not.