Home Engine Systems Performance Transom Support Plates Transom Top Washer Plate CMC Transom Top Washer Plate $42.19 Transom Top Washer Plate quantity Add to cart Product Details Product Details Hole Centers: 12-7/8″. Made of strong 3/8″ 6061 T6 extruded alloy aluminum. Eliminate bolts “biting” into transoms. Distributes loads on high performance engines.