Raw water pump failure - Need help

[Sbt3]

I had a very similar problem today when I put my boat in and am down to thinking the pump is bad. I am pretty sure I have it reassembled correctly. I tried putting the pump on both ways because I figured I could have put in on backwards the first time. I know my plate is there and the gasket is good. It wont prime the line. If I pour water into it it will shoot it out for a second but then stops. I burned up my first impeller but ordered two so I put the second one in and it does the same thing. I thought it was something to do with the strainer but that seems ok too.

Coloradonautique- did the plate end up solving your problem? Maybe I will look into it again.

Also should it prime and shoot water at just an idle? I had the boat on the lift and would start it but nothing would come out and the strainer wouldn't fill. I didn't try reving it though. I know the intake isn't clogged cause I run my ballast off the same line and those are working fine. In fact I put the line from one of the pumps into the cooling system to get back to the dock after I noticed there was a problem with the raw water pump.

Stan

[j2nh]

Had a buddy do this last summer. Changed the impeller, brought it out to the lake and it overheated. Pump on backwards.

The other thing to look at is the hoses on the inlet side. Make sure you do not have a loose hose that can cause an air leak. Water is hard to pull so the pump will go for the air if it can find it.

Look at the water strainer. Is there a gasket? Without one you could have an air leak.

Nothing more frustrating than a broken boat.
Let us know how this turns out.

[coloradonautique]

Sbt3,
Yes the spacer plate fixed it. Definitely won't work right without it. My pump (once fixed) pulled water from a bucket on the driveway all the way up over the gunnel with boat on the trailer. That is a long way and at least 6 vertical feet so there is definitely something wrong with your pump/setup.
I think it would be really rare for the pump to mechanically fail. I feel it is just too simple of a design for that kind of failure.
Check out the link earlier from linebacker with the sherwood pump breakout. It gives you a good picture of what parts need to be where.
Here are the things I would check in order of importance:

1) Water strainer clogged? O-ring okay? Everything tight and no air leaks?

2) Transmission cooler (port side of engine down low): No clogs and tight clamps?

3) Water pump
- Flat head screw on pump should point to engine
- Check impeller key, gaskets and all parts are correct and working.
- Check intake and exhaust ports are not clogged
- Try my blow test: Blow air into the intake and block the exhaust. See if holds pressure. You can do this with any path of hose to see if it is leaking along any connection.

I am assuming you have the exhaust hose disconnected from the thermostat and are checking flow at that point. You might try filling the strainer and intake hoses just to see if the pump will prime but I am thinking there is something more serious than that.

It should prime at idle although some other folks have experienced problems if not running at least 800 rpms. Technical spec says pump should fill a 5 gal bucket at 3000 rpm in 13 seconds.

Good luck. Post if you get more details on the problem.

-Lorin

[linebacker55]

Lorin

Everything run right after you put it back together? Sent you a PM.

[RCHANDED]

I marked my pump during winterization, so as not to re-install it backwards, however, I forgot what the marks meant, (what an idiot)

So, I am reading here that the screw should face the engine, is this true on both RH and LH rotation boats?

I have a 92 Excel V-drive, I'm thinking the screw faces out.

[Sbt3]

Yeah I think I tried most of those things already. I messed with it quite a bit. I am stuck out of town for the week for work so I won't be able to work on it until next weekend. Hopefully the time away will help me find the problem next weekend. I am sure it is something simple. Like you said the pump is pretty simple and it was working fine before the impeller change which indicates it was something I did unless I had water in it over the winter and something cracked somewhere but it all seemed to look ok. I will report back next weekend if I find the problem.
Stan

[DanielC]

Looking at the end of your Ford engine, that has the v-belts, on it, towards the transmission, if the engine rotates clockwise, the screw goes in to the engine. DO NOT LOOK AT THE PROP. YOUR TRANSMISSION MAY OR MAY NOT CHANGE THE ROTATION! If your engine rotates counterclockwise, the screw goes out.

[coloradonautique]

Linebacker, Yup the spacer plate fixed it and it is running like a champ now. Got your PM, you should see something in the mail soon.

RHanded, Not sure about RH rotation engines and the screw. If you look at the way the pump is designed you should be able to figure out the input vs. output. Here is my thinking on it.

1) Note the rotation of the impeller with the pulley off.
2) Pick one blade and mentally follow it around the rotation path.
3) The intake should be the opening crossed just AFTER the CAM (the thing the screw holds in place)
4) The output should be the opening crossed just BEFORE the CAM.
5) The longest path of curved pump body the blade passes should be between the intake and output, directly across from the CAM.

The CAM has a blockage built into it so I think the way the pump works is by pulling water from the intake, around the body and to the exhaust where the CAM starts and squeezes the blades forcing the water to take the only path out.. the output port. That's my thought anyways. I never took fluid dynamics in school so I could be WAY off.

Post a pic and I might be able to figure it out.

Cheers,

Lorin

[RCHANDED]

Thanks for your help guys
I found that on RH rotation engines the water pump has the screw facing out. This is how I ended up installing it and everything is working and ready for summer!

[Sbt3]

Well mine turned out to be the pump. I got a new one put it in and works great. It still bugs me what was up with the old one though. It really shouldn't be bad unless the shaft seals went out or the surfaces we worn that the impeller contacts.
Now the bad news. My boat has a shake when underload. I am pretty sure I smoked a head gasket during the overheating incident. I plan to do a compression check this weekend to confirm my suspicions.

[DanielC]

Coloradonautique, good explanation on how the pump works. Everybody, propeller rotation is not necessarly engine rotation.
I have seen waterpumps on high hour engines just not pump as efficiently, even after replacing the cam, and polishing all the grooves and were in the plate that the impeller rides on.