Circuit breakers are not a protection device intended to replace good sense. If you already anticipate a serious problem, deal with it at the source: reconfigure your arrangement to ensure the wiring is routed clear of the identified pinch points.
Circuit breakers are not as simple as fuses. For an approved circuit breaker of less than a 50 amp rating, the testing criterion is that it must trip within a maximum of 2 minutes at 200% of its current rating and trip at 135% of it's rating in less than one hour. Before the breaker trips you may have a fire to deal with. In prolonged use, a marine circuit breaker is exposed to a corrosive environment that may disable it entirely.
Depending on the round-trip length of the wire run, a nominal 30 amp load at a minimum of 12 volts, requires at least 10 ga. copper wire, properly terminated. A starter motor, either stalled or operating at lower voltages can draw substantially more than the nominal amperage. For this reason, wiring to starter motors is not conventionally fused by ABYC standards. If you decided to fuse your circuit, you’d need to know the cranking amps of your starter, probably 30 to 40 amps for your kicker. Then you’d choose a fuse size that won’t cause nuisance tripping., like 1.5 times the max cranking current. Lastly, you’d make sure your battery wire to starter can handle that 1.5 x current rating.