water pump screw question

[holtcl]

Was coming back from a cruise recently, went down for the routine engine room check, and found that raw water was spraying around the STBD engine room, looked like it was coming from the area around the impeller plate. I shut STBD engine down, tied down the gear, and came home on one.

Today it was warm enough to fire the engines again so I figured I would try to find out where the water was coming from.

Turns out that the screw that sits on top of the raw water pump (where the impeller is) has apparently broken off. See pics.

Questions:

1. What is that screw for?
2. How deep down does the screw go (e.g., how long is it)?
3. The old screw was bedded in; recommendations on what bedding material to use when I replace with a new screw?
4. Other words of wisdom?

I assume that I will have to get the broken off part out with something like an easy out. I just don't want to go too deep when drilling.

Thanks in advance for your help.

Cheryl
Cinderella
1971 53 MY

 

[rmatt]

Looks like the screw that keeps the cam in place. The cam is the piece that dis-forms the impeller allowing it to pump.Hard to see the pic. If that is the only screw that goes into the area the the impeller is located, then it is the cam screw. You will have to take the plate off the back, remove the impeller and remove the cam. Remove the broken screw or replace the cam and screw with sealing washer.

 

[SeaEric]

+1. That's got to be the screw that holds the cam in.

 

[MikeP]

Yep, that's crevice corrosion - I've had exactly the same thing happen to the small screws that are in the bottom of engine/genny mufflers as well as that cam.

Assuming the cam itself isn't damaged, you can just pull the cam out (after removing cover plate/impeller as noted) and get a new screw - It's a standard machine thread though I don't remember what thread size. Go up to the hardware store with the cam (I can never remember if it's Ace or True-Value though I should be a stock-owner in the place by now). Ideally you want bronze screws but 416 SS is right next to bronze on the cathodic scale - there isn't enough difference to matter in a normal lifetime. It's possible that WM might have bronze screws; I doubt that the Hdw store will though they might. But it really won't matter - 416SS is fine. DO NOT use brass screws.

Might as well buy two screws and do the other pump as well...

 

[saltshaker]

Now would be a good time to evaluate the pump and possibly rebuild it. I would think a new impeller would be the bare minimum.

 

[holtcl]

Thanks this is VERY helpful- I did the impellers last year so I thought I would wait until next year on those, but at least this gives me a chance to examine it; and maybe do both pumps while I am at it.

What is involved in "rebuilding the pump."

Cheryl
Cinderella 1971 53 MY

 

[MikeP]

I have not rebuilt the pumps on our Hatt though since I install new impellers every year, I'm "in there" to see it regularly. On other pumps that I have rebuilt that look similar, there are usually two bearings and a couple of seals. Pulling the bearings/installing new ones can be a little difficult if you don't have the tools to do it.

Getting them out is no big deal because you don't care if you mess them up. Usually you can press in new ones with a vice or the old time way - an appropriate size socket and a hammer! But the bearings usually have to be seated in the housing and on the shaft so you have to be careful about where you apply the pressure. If you seat the bearings in the housing and then try to press/tap the shaft into the bearing, you will damage the bearing. If you seat the bearing on the shaft first and try to press/tap the bearing into the housing by tapping/pressing the shaft, again, you will damage the bearing. Usually you can come up with various sockets - deep well and standard - and arrange the proper support for pressing/tapping.

I'm sure you can find appropriate pics of this on line somewhere so it actually makes sense.

Just be careful - if you damage a new bearing - which probably won't be visible, you've created a problem that may not exist now. Obviously any local shop could rebuild the pump but that's no fun and where's the satisfaction in that?

It's easily do-able for you but if you have never done that sort of thing before it can look a bit bit formidable the first time.

 

[holtcl]

Thanks Mike- that's helpful detail. Maybe something dad can help me with if I decide to delve in.

Cheryl
Cinderella
1971 53 MY

 

[MikeP]

Yep, I guarantee he has done plenty of that sort of thing - with the correct tools!

 

[holtcl]

Got into the pump today- store didn't have bronze bolts so I got the stainless. Job was easy and I understood the issue when the impeller came out with the cam on top- 'ah ha'. Thanks for all your help!

Cheryl
Cinderella
1971 53 MY

 

[SKYCHENEY]

While you have it out, check the back wear plate.