After a prop change...

[Learn2surf]

Will it be pretty obvious if the prop isn’t on properly?  I don’t usually do any work myself...but I had to change the prop as the dealer is busy. Everything seems smooth like before. I am wondering if I would notice or would the boat compensate a bit until things start to break.  Thanks!

[mikeo]

If you didn't get the prop on properly then it would fall off or the boat wouldn't go. Here's a few things to check, at least mentally (did I do that?):

1. Prop shaft looks good, no damage, isn't bent. If you think it's bent, that's a different question.
2. After you pulled the old prop (SAVE IT, IT CAN BE REPAIRED!) did you put a new (or re-use) the brass key in the driveshaft? No amount of tightening the nut is going to keep the prop from spinning on the driveshaft without a key installed.
3. After you put the nylock nut back on the driveshaft, did you put a new cotter pin in the hole so the nylock nut doesn't spin off? 
4. Did you manually spin the prop to make sure there is at least 1/2" or more of clearance from the bottom of the boat?
5. On your first run out of the marina, don't put a rider in the water. Stop at the end of the 5 MPH zone, take off like you have a rider, get up speed, feel for any new vibrations, slow down/stop. Go in reverse, not fast, but enough to move the boat. If everything feels like it did before you swapped the prop, you're good to go. If you didn't do, or fail any of the checks above, re-check your work.

Swapping a prop is like changing a tire, everyone should know how to do it, some don't. Some people are too good at it, either from practice, or just because.

I was comparing the performance of different props on my boat early last summer. I got to the point that I could swap a prop at the dock with only a few dives underwater. The water was clear and shallow enough that I had to be careful not to hit my head on the bottom of the boat, but I could easily pick up any tools I dropped. Swapping a prop in the water is possible, but not recommended. I didn't want to block the ramp on a busy day when I was testing props.