The Brand/Make or Model of the motor would help, I will guess that it is an Outboard. Most Outboards have a Release and Set pin that is on a hinge just beneath the Cowling, usually Forward part or just under the Motor Cover,(cowling), in the front of the Drive Shaft.
You can find out this data and get much more info at BoatSafe(d0t)com.
I strongly suggest that you look at that site and at least take the safe boating class for your state, or at the least brush up anything that you are uncertain of.
Wear a PFD. please.
Boat Safe, please.
iboat is a decent site also.
I also included a link to a free PDF for Honda OBs, I have a Suzuki, Evinrude, Johnson, Tohatsu , Mercury and others that I use on my sailboat, all are 1980s-1990s and all are below 10hp, Long Shafts.
I also own a Bass Boat/Bay Boat that has a 2003 50hp Evinrude on it.
I have been boating safe and enjoying the ride for 40 years now. It is all in the preparation and the details , but do not over complicate a simple rule, USS always has the Right of Way, so do many barges.
You also may want to look at Your State (d0t) com and look at the Requirements that vessel needs to meet to be operated.