Optimax Hose Flush Attachment Plug
 

So I've been using the hose attachment on the back of my Optimax for a while now to flush it, and every time I take off that little plug in the back, I wonder, is that part necessary? Some part of me wonders why they would put that little piece of plastic on the back, since obviously one day I'm going to drop it in the water and lose it. Does anybody know if that part is necessary? If so, I might try to order a couple more to keep in the boat. If not, I might try to put a quick connect attachment on the back to save myself the pain of unscrewing the thing every time.

I have a quick connect on my 300xs that stays open

Not sure on the necessity, but had to get a replacement before and found it in stock at Redmonds.

Can't say for sure, but pretty sure it's necessary. Believe it closes the cooling system loop. I have the quick disconnect and it's nice. Warning, you can't just use a regular quick disconnect. The one made for this has a check valve in it.

I would agree, seems like having it removed would effect the vacuum

I have a Suzuki outboard and it has two hose connections on it and both have removable plugs to attach the hose to. They have to be put back or the engine will overheat(this is per the manual). Do you have a manual to refer to? I am pretty sure if it is a part on the motor then its there for a reason...