I have a PRU-3. It does not row well at all. Even if you get it going straight, if you then coast for 8 or 10 feet on a dead calm day, it will turn sideways, all by itself. Rowing against a 2 knot head current or a 10 knot head wind is a tough haul with little headway.
It's a great little boat for what it is intended for, which is being stored a lot & used a little. I can go from rolled up in the bag, to in the water with motor running, in just under 6 minutes, if I use a battery powered leaf blower to inflate it & then finish off the air pressure with the foot pump that comes with it. Even my silly little 21' micro-cabin boat, is able to store the PRU3 easily when it is rolled up. Actual boating performance is not that good, but it gets me by. If I needed to use it more often, I would want a hard bottom boat.
A 30# thrust trolling motor ($100) with a group 27 battery (another $100) will get you about 3 knots & go for about 45 minutes to maybe an hour if you are lucky, with 2 people in the boat & no current or wind to fight.
A 2.3 hp gas outboard moves it about 4-5 knots at 1/3-1/2 throttle unless you load it like a pig. A 3.5hp does just a little better. A short shaft outboard will cavitate badly at 1/4 throttle if you have only a single 200# person in the boat. Loaded with twice that weight, the short shaft is fine. A long shaft motor works well with lite loads, but adds stress to the transom, so I would derate the 6hp max rating if using a long shaft.
Even with the motor, the PRU3 slides sideways pretty badly if there is a cross wind. Even 5 knots is noticeable. 10 knots makes you pay attention. 15 knots makes you concentrate a little harder.
There is also the RU3, which is 2/3 the price of the PRU3 & about the same size/weight. The PRU has tubes that are an inch larger in diameter & has slightly higher HP & weight capacity written on the tag. When I bought the PRU3, I was told that the RU was PVC & the PRU was Hypalon. I now see on the website that both are listed as being PVC. I have one unconfirmed report that in the old days, the PRU was made by Achilles. Mine came from China. I've probably had it for about 3 years now. I've probably used it 15-20 times.
If I were to add a keel to the PRU, I might choose to add 2 small dagger boards on the back of the transom. It would also be nice to have a pair of wheels back there for beaching. Plastic wheels encased in a cover that mimics a dagger board might be a good way to go.