There is no plug for this transducer – unless you create your own. Usually the rooster tail is caused by the transducer being too low in the water but this is sometimes necessary to get depth readings at higher boat speeds. It also exposes the transducer more to damage by floating debris, stumps, tress and rocks…
What type of boat do you have and does it have a fiberglass hull? You may have to post some pictures of your boat hull for us to look at alternate mounting locations.
Whether you can get a depth readings at higher boat speeds is a function of the shape of your boat’s hull, how the water flows off of it and where you can mount the transducer. Not all boats have a mounting location that will allow for this and also allow the Si sonar to work at its best.