The Volvo 280, 290 and 280 Duo-Prop incorporate the anti-cavitation plate as the exhaust port. Viewed from the rear, it is a wide flatted oval opening with a rubber flat (located directly above the prop. These drives are the only ones which require brackets to mount the Doel-Fin. The #445 Bracket will fit the 280 and 290 drives, whilst the 280 Duo-Prop and most 290 Duo-Props will require a separate bracket (#446 Bracket).
The brackets will fit around the exhaust port.
1) Using the brackets as templates, drill four 5/16" holes into the exhaust port (two on top and two on the bottom).
2) Slide the two 2.5" bolts from the bottom through the holes in the plates and exhaust port.
3) Secure with the nits and washers provided.
Doel-Fin wings can then be mounted through the tabs on the sides of the bracket. Secure by the hardware provided with your Doel-Fin package.