TOPIC: Advice on Repair of Cav. Plate-Merc 400

Not sure if that is the correct term, but I'm wanting to know how to repair this, (pic.) What type of metal is this? I do not have the missing piece.
Just finished stripping all the lower unit,getting ready to replace impeller. Also having hard time trying to shift FRN. Controls are off but the only way can get into N is by lifting the spring on Mech. Could someone have taken unit off and not lined up right?
All info appreciated, Milton.

I believe it is cast aluminum. If you have a weld shop close by they can do repair work like that. I had a local prop repair business replace a skeg for me. They clean up the break area, weld in a new piece of aluminum and fair it. You'd never know there was a break. There are some pointers in these strings how to line up your shifter. It's tricky but works. I had to do it on my Mark 58 but it's been a few weeks back and I forgot. You know how that goes.
Cal

63 Sabre---- Appreciate the info, Took the lower unit off this morning, had my brother tig weld/alum. rod, can't even tell.
Now to get to the impeller and replace it. Guess I'll figure out the shift problem.
Thanks again, Milton

Trying to get to the impeller but not having any luck. Gonna have to come up one with or make a tool. In the pic.will counter clockwise remove this?
Thanks yall have been so helpful.
Milton

yes its a standard thread sometimes heat is required as well as a tool
you can make a tool but there happens to be a correct factory tool on ebay now, if your going to keep your merc you should buy the tool
impellers should be replaced at least every 2 years

cgi.ebay.com/ebaymotors/MERCURY-OUTBOARD-LOWER-UNIT-TOOL-MARK-35-55-58-PUMP-/120847108510?pt=Boat_Parts_Accessories_Gear&hash=item1c230c899e

mlg. The plate turned out excellent!
Just went through this procedure awhile ago. Madprops has some really good pointers on how to change the impeller. Here are some pics I took when I did mine. The "cap" is lefty loosey. I made a "tool" if you want to call it that with a pipe nipple and two 1/4 bolts then used a pipe wrench to loosen it. The wierd(?) picture is of a short section of pvc pipe with the inside beveled to install the new impeller. I lubed everything up with cooking oil, twisted the impeller into the pvc and just slid it onto the drive shaft and into the pump housing. Don't lose the little roller bearing type key that fits in there otherwise the impeller will install but will not turn with the shaft. Also make sure the impeller is twisted in the right direction turning clockwise.
Cal

while you have the water pump cap off you should consider replacing the seal in the cap as well as the impeller. IF you can get the cup out of the lower unit replace the seal in the bottom of the cup as well. Check the seal surface on the shaft while you are there.

nice job on the weld!

love the jet prop on a non jet lower.

doh! I just noticed that! not enough coffee this AM

Thanks 63 Sabre for the info on the impeller tool.
Built one like yours and with help from 3' cheater pipe & heat it finally gave up the ghost.
Now to locate impeller (locally), maybe the cap seal and I will be going back together.
Thanks again,
Milton
P.S. So when I'm looking down driveshaft, impeller will rotate clockwise?

One more question. Does anyone have a part # for impeller (Merc 400)? How about water pump seal?
All info appreciated.
Milton

impeller 47-20268 superceeded to 47-65959.for starters mercury should have them.