Pelher;
You did not give us enough information to properly answer. Is your engine electric start? Generally if there are wires comeing from the engine for an 8 hp motor, it is electric start. That being the case, the two wires are either color coded for example red for positive with black for negative. In some, one of the black wires may be colored coded white which is for the positive. That being said, the positive should go to the positive side of the battery; otherwise, you could damage the alternator and/or battery if cross wired.
If the cables are thick and it is electic start, for quick connect/disconnect, use of a two plug trolling motor plugs is ok to use but make sure of your wiring connections that red goes to the plus side of the battery. Also use minimum of # 6 cable from the plug to the battery is a must as the electric start pulls alot of power. Thinnk of heat going thru a large cable vs a very small cable. the very small cable will burn up for example a #18 wire will burn up.