Winterizing 350 mag and water pump issues !

I have a 2006 Crownline 240EX with a 350 mag and a bravo III drive. I have 2 questions.

1. I went to the lake this past weekend to winterize the boat. I was told it had 5 blue drain plugs. I could only find 4. 2 on bottom left raw water pump, one above the other. One plug on bottom right on drain housing where many hoses come together. One up top near thermostat housing. Can't fine #5?

2. I started engine and the belt squealed real bad and noticed raw water pump locked up. I took belt off and could turn it counterclockwise but not clockwise which is the direction it should turn, I think? I notice a lot of times when I shut the engine off it kind off runs backwards for a millisecond as the engine stops. Could this have turned the rubber fins in the water pump backwards and now it is in a bind and wont flip them the other way when I start it. Like I said, I can turn it backwards by hand but not clockwise.
Any help appreciated.

Marty in Arkansas

same engine
1. Suggest you have a 3 point drain system. The one at the thermostat is a vent. Suggest you buy new drain plugs and remove/replace all of them and grease the threads when you install them. The heat deteriorates the plastic and they break-off. Replace every few years

2. No idea but recommend you replace the impeller. Might want to remove the belt and test the pulley's

I discovered this when I rebuilt my water pump some years ago... If you install the impeller "backwards", ie. fins pointing the wrong way, within a revolution or two of the pump, they reverse and point in the correct direction. What you are seeing is symptomatic of a water pump impeller that has lost it's flexibility and, as "sab" suggested, needs replacement. Suggest , if it's a plastic body pump, that you get the whole "kit" and replace the plastic housing and wear plate as well, not just the impeller. Be careful not to reverse the hoses when you reassemble. If the old impeller is missing any pieces... FIND THEM... most likely hung up on the input to the engine oil cooler, usually the first thing down stream from the pump output. Lube impeller with soapy water to facilitate install and to provide some lube during the first start. NEVER RUN these pumps dry. Supposedly 20 seconds running dry kills them. OEM kits ONLY!!

Thanks for the reply!
I took the belt off and couldn't turn it clockwise by hand and I am a pretty big guy. I could turn it counterclockwise though. It has a metal housing. I think I am just gonna order a new pump and put it on next spring.
Again, thanks so much.

Pumps not turnable by hand in reverse... The pumps are designed to be rebuildable.... you may change your mind when you see new pump price...

You are right, they are a little pricey. Thanks for the help everyone!!!