Another idea ....
Put a 90 elbow between the cooler/riser box and the exhaust manifold mounting the riser/box crossways or athwartships. Rigid mounting to keep the riser moving in sync w the engine will solve the mounting issue. Some changes in the wet exhaust run may be necessary.
Re the space in your boat this could be an advantage and a side exhaust may even become attractive.
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Eric
North Western Washington State USA
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