A 40 HP on a 490 rib is a poor performer, worst being a 4 strokes which is kind of slow on hole shot. Install an induction tach, go for a wot spin with you alone on flat glassy waters and check max achieved RPM with current prop.
Check manufacturers working wot parameters to compare, will know how much under propped you could be. Can optimize engine performance by raising RPM to near max wot RPM playing with prop pitches. Withoiut a tach you're blindless playing with pitches.