A 30" shaft will work but a 36" shaft is better. But the power should be enough for trolling and it will get you wherever you want to go faster than fin power alone. However, I think the oars will probably move you faster than the light motor for high speed motatin'.
You won't know for sure unless you try it. If you have the motor then rig it up and give it a shot. Just be open to the factors I mentioned and be prepared to upgrade to a longer shaft motor.
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