OK - maybe they're not going to knock 20% off... but I'm well within my rights to a replacement as technically it is faulty:
Under the Consumer Rights Act you have an early right to reject goods that are unsatisfactory quality, unfit for purpose or not as described and get a full refund.
But this right is limited to 30 days from the date of purchase of your product.
However, this right doesn’t apply to faulty digital content.
If that's the case, factor in shipping costs to the dealer, covering return costs to shop, labour to swap the transom wheels over, Honda's internal costs, repairing the boat which is now second hand, depreciation on said boat, etc... 20% would probably be cheaper to them ;-)