All the listed home remedies are temp. None work for the long run, even a cage trap and they will return after a hosing. I would not recommend discharging a weapon of any sort in an area not allowed, many just want a reason to take your property, and when checks for life come in shooting cats will qualify you same as a serial killer. Of course the old conibear 330 or even a 220 will always work and is quick, silent, humane and most definitely permanent as is the cage trap and a 45 gl garbage can of water.
But as this is 2020 and your neighbors cats and wild feral cats have the full right to **** and destroy your property without retaliation or consequence, you should build an enclosed facility to safely store your boat, or move it to a facility or place that has no cat issues. Be calm, be kind and be cat safe.
HM