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Old 03-09-2015, 09:52   #1
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Water leaking from seawater pump

Hey gang,

Technical question for you. I have a water coming out of my impeller housing.

It's just a drip when the boat is off, but turn it on and rev the engine - the more the impeller turns, the more water comes out.

This is my engine / sea water pump unit:

MerCruiser 7.4L BRAVO (GEN. V) GM 454 V-8 1992-1996 SEA WATER PUMP Parts

The marine mechanic said to replace the whole thing. Which is $766usd. I'd hate to replace the whole thing if I could just replace the part.

He thought it was the bearings, although another mechanic said something internal might be bent. So why replace the whole thing?

Regardless - anyone have any familiarity with this? Can I just pull it off my boat, rip it apart and inspect it myself to see what's up? What am I looking for?

Is it easy to pull off? I'm mostly worried about the fuel pump application.

Any insight would be appreciated!
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Old 03-09-2015, 10:01   #2
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Re: Water leaking from seawater pump

A few comments.

First, it is 99% certain that Mercury did not build this pump. Almost all marine engine companies buy the pump from Sherwood, Jabsco or someone similar. If you can figure out the generic equivalent you can probably find one online for 25-50% less than the Mercury part.

Regardless of who made it, unless the pump is seriously damaged, corroded beyond repair, etc it is very rebuildable. Look at the diagram you included and you can see a whole list of gaskets, seals and bearings for the pump.

If you are up for it, take the pump off, take it apart and check it out.
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Old 03-09-2015, 10:04   #3
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Re: Water leaking from seawater pump

By the way, based on your description of the situation, unless your mechanics have x-ray vision I would recommend finding a new mechanic.

If the pump is completely eaten up with corrosion or the pulley very obviously bent and wobbling there is not way you can diagnose the pump without removal and disassembly.


The guy that wants to just replace it is either lazy or just knowing his hourly rate figures the cost to rebuild the pump would cost more than a swap out.
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Old 03-09-2015, 10:19   #4
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Re: Water leaking from seawater pump

I agree with Skipmac.

It's a Quicksilver pump, with luck, you'll just need to replace seals and bearings, and the impeller while you are at it.

Seals and bearings would most likely be available from a bearing shop, so no need to pay OEM prices.
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Old 03-09-2015, 10:20   #5
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Re: Water leaking from seawater pump

Quote:
Originally Posted by skipmac View Post
By the way, based on your description of the situation, unless your mechanics have x-ray vision I would recommend finding a new mechanic.
Agree 100%.

It visually seems fine, so I'm thinking of just taking it off and checking it all out myself. Then replacing what needs to be replaced.

Seems like a daunting task with all the parts though...
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Old 03-09-2015, 10:29   #6
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Re: Water leaking from seawater pump

Many of today's mechanics are parts changers. They don't fix anything. Some of that is because of the labor rates. If it takes more labor time to rebuild rather than replace, the new pump is cheaper. But if you rebuild it, the labor is free even if it takes you twice as long.
The most common leak is the shaft seal. Often the seal goes bad because the bearings are bad. Usually replacing the bearings, shaft seal and a new gasket solves the leaks. Bearings have numbers on their sides. If you have the time, you can buy them online for much less than a marine manufacturer. Inspect the shaft for pits where the seal contacts it. If pitted you probably need to replace the shaft.
I rebuild my pumps, 2 mains, 2 generators = 4 salt and 4 fresh pumps. About 2 hours each including unmounting and mounting.
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Old 03-09-2015, 10:31   #7
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Re: Water leaking from seawater pump

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About 2 hours each including unmounting and mounting.
Great advice. Based on your experience, I think 2 of your hours translates to roughly to 10 of my hours.

I really want to get better at this stuff, and the only way to do it is to try, even if it means mistakes.
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Old 03-09-2015, 10:40   #8
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Re: Water leaking from seawater pump

Try this, same issue:

Raw water pump failure on Westerbeke 70 - Cruisers & Sailing Forums
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Old 03-09-2015, 12:12   #9
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Re: Water leaking from seawater pump

Quote:
Originally Posted by radar_x View Post
Great advice. Based on your experience, I think 2 of your hours translates to roughly to 10 of my hours.

I really want to get better at this stuff, and the only way to do it is to try, even if it means mistakes.
This might be a good one to try. There are a number of parts but nothing super high tech, tight tolerance and such. Basically it would be hard to screw it up. Not impossible but you would have to work hard to make a mess of it as long as you remember how to get it back together.

What I do when disassembling something with a lot of parts is one or more of the following: draw a diagram, take pictures and lay the parts out in the order and orientation they came out (make sure your wife doesn't come by and straighten up if you leave it sitting too long).

Standard tools should do most of the job. The only thing you might need if you don't already have them is a set of snap ring pliers.
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Old 03-09-2015, 12:26   #10
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Re: Water leaking from seawater pump

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Originally Posted by skipmac View Post
This might be a good one to try.
Awesome. This is just the encouragement I needed.

I have a complete service manual for my engine that tells you exactly how to pull it all apart and put it back together, so I'm feeling slightly confident.

I don't have those pliers though - so I'll have to pick them up.

I'll probably post pics here if there's something I can't figure out too.

Thanks so much for your input. Makes me feel a lot better about attempting this.
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Old 03-09-2015, 12:31   #11
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Re: Water leaking from seawater pump

Quote:
Originally Posted by radar_x View Post
Awesome. This is just the encouragement I needed.

I have a complete service manual for my engine that tells you exactly how to pull it all apart and put it back together, so I'm feeling slightly confident.

I don't have those pliers though - so I'll have to pick them up.

I'll probably post pics here if there's something I can't figure out too.

Thanks so much for your input. Makes me feel a lot better about attempting this.
Well to be completely honest. This is a horribly difficult, extremely time consuming job that will destroy your engine and maybe the whole boat if you get the tiniest detail slightly wrong.

We're all just saying this to suck you into the job so we can laugh and gloat later.
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Old 04-09-2015, 09:33   #12
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Re: Water leaking from seawater pump

I tried to repair my pump but I could not remove the old bearings- they probably were pressed in. If your bearings come out easily then it will be an easy job. I ended up buying a new pump but later found out that many companies will rebuild your pump for less than half the price of a new one.

My pump had a small leak at the shaft. Changing the seal wasn't enough because the shaft was pitted and quickly destroyed the new seal. Someone suggested just moving the seal slightly so it doesn't rub on the rough part of the shaft. I haven't tired this- it might extend the pump's life.
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Old 04-09-2015, 09:54   #13
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Re: Water leaking from seawater pump

Here's what I do whenever in the same situation like I was four weeks ago. I replace the failed pump with a new pump, then rebuild the used pump and keep it as a spare.
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Old 04-09-2015, 10:05   #14
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Re: Water leaking from seawater pump

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Here's what I do whenever in the same situation like I was four weeks ago. I replace the failed pump with a new pump, then rebuild the used pump and keep it as a spare.


Exactly!

However, like Eveningtide, the last raw water pump I disassembled had been neglected too long by the PO and was corroded beyond repair. Some of the bearings and seals were beyond recognition and corroded the inside of the pump housing as well, and the shaft was pitted and seriously scored where the bearing rusted up. In that case even with zero cost for labor it wasn't worth the rebuild. I did get a couple of spare parts out of it.
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Old 04-09-2015, 10:05   #15
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Re: Water leaking from seawater pump

Yeah, I'm going to tackle it in a couple weeks after when I have some dedicated time to spend on it.

It's going to be interesting for sure...
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