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Raw water pump

8K views 56 replies 14 participants last post by  cardiacpaul 
#1 ·
Yet another question. I am replacing the raw water pump. On land I would use teflon thread tape on the 90 Degree elbow threads to make a good seal. Is it the same practice for raw water, or will it eat away the tape? I was also told that some use polyurethane caulk to make the seal, is that correct?
 
#2 ·
Teflon tape please... not polyurethane caulk... Teflon is far more chemical resistant IIRC...
 
#5 ·
Yes, unless you like tiny, hard to trace, leaks...

BTW, do not take any agreement between CD and me to be an indicator of future agreement...
 
#7 ·
I would reconsider teflon/caulking the threads on the HE zinc, the more you insulate the zinc from the HE the less effective it becomes. It is conceivable that the effects of the zinc could be completely negated, therefore I would recomend no teflon tape/caulking . This is one time a minor leakmaybe acceptable.
 
#8 ·
Svwhirlwind's got a very good point... nix the teflon tape on the zinc... he's completely right... it would act as a galvanic isolator...which is the last thing you want on a zinc. D'oh... my bad. While I don' t like tiny leaks, corroding heat exchangers are far worse...cause then you get a lot of them, plus a costly repair... ;)
 
#9 ·
Yes, you don't want to isolate the zincs....

Technically the teflon is really there to act as a lubricant/friction reducer and the tapered threads should seal themselves by design - but the tape will of course make up for some flaws or lack of tightening and is routinely used to reduce the possiblity of leaks.

An alternative to tape, especially if you are dealing with a system where you don't want an errant piece of the tape to enter the system is a teflon-based paste-type sealant.
 
#12 ·
The new pump is in and the new hoses are on. The engine started, and after about a minute, the system primed and I got water out the exhaust. Unfortunately it seems like I am getting less water out. The pump is working, and when I go to high idle, I get more water out. Temp stays where it normally does, no overheating. I have not cleaned out the heat exchanger yet. Strainer is empty. So, I am wondering if using hoses that are too small would cause less water. I kind of doubt it, though. I bought 1/2 inch to replace from the strainer on to the engine and the rest of the system. They were very tight going on, but the next size up, 5/8, slid right on, and that seemed too loose. The old hoses weren't marked. I don't think 1/8 inch would make a difference. Could it be that the old impeller was spinning more freely from wear, and sending more water?
I get a spurt about once every 45 seconds at idle, does that seem right?
Oh, and no tape on the zinc threads is holding the seal.
 
#14 ·
The previous hoses didn't have a size on them and they did not match up with the Trident hoses that I bought. Either too big or too small. I didn't measure the nipple, unfortunately. I may have to go back and do that. I will have to keep an eye on the temp and use that as my indicator that everything is ok.
 
#15 ·
Bestfriend-

The hoses are supposed to be very tight going on... but they should fit over the fitting without needing to be cut, but should need to be forced. If they don't need to be forced, then the hose is too big.
 
#16 ·
something must be up with the moon

Heres the latest. I started the boat up today and got no water out the exhaust. Two days ago I was getting what I thought was not enough, but I was getting some. So, first I took the hose off the seacock and made sure it was open and flowing, it was. Next, checked the strainer, no blockage, but the water did not taste very salty(I had filled the strainer with fresh water to help prime). I deduced that the pump was not working. So, next I disconnected the pump discharge hose and fired up the engine. No water coming out, not even a breeze coming out the hose. I took the pump off and guess what, a whole bunch of tiny rubber pieces came out. Then I looked in the elbows and saw that even bigger pieces were blocking the passage. So, somehow the impeller shattered. Back to the store.:mad:
 
#17 ·
BF - was it a new pump or just an impeller change? Either way, maybe you got stuck with an impeller that had long outlived its shelf life.

Did you have the pump apart before/during installation and notice the condition of the impeller at that time?

These impellers are usually pretty tough - it would be rare for a good one to fail so soon. This one sounds like it self destructed soon after startup.

Real important, obviously, to get all the "bits" out of the HE system.....
 
#18 ·
Faster - It was a new pump, and I did not take it apart. I haven't cleaned out the exchanger yet, that was my next project, so that worked out ok. I had read on another board that it didn't matter which way the impeller was put in because it was rubber and would flip the right way. I find that very hard to believe looking at the innards of my old one. The tolerance seems much too tight. I think this one was put together wrong.
 
#21 ·
Impellers can get pretty brittle if they're run dry or get too old. Globe makes some that are designed to resist burning out if run dry. Once the impeller gets brittle, the blades break off and get stuck in the cooling system... which is very bad.
 
#22 ·
bestfriend said:
... I had read on another board that it didn't matter which way the impeller was put in because it was rubber and would flip the right way. I find that very hard to believe ..
Actually it's true - the impeller will flip itself around if installed backwards, but I usually try to get it in in the correct orientation "just because"..

When you buy a replacement (which obviously you'll have to do) it should come with a small capsule of silicone lube to put on the impeller to help it seat itself and prevent damage during the initial "dry" run til it primes itself.

Luckily you don't have to find a large number of bits... I'm actually surprised it quit pumping altogether with only one impeller blade missing..... maybe there's more to this yet?
 
#23 · (Edited)
What really irks me, besides the extra work, is that I emailed sherwood and asked them if I needed to lube anything before install. They said no.:mad:
Oh and I won't be "buying" a replacement. No way. This ones on them.
I think the blade that broke was blocking any flow of water. The pump was probably still running.
 
#24 ·
The impeller may have been "prelubed" by Sherwood I suppose, but if it was on the shelf forever the advantage would be lost anyway.

If the blade that broke off is big enough to block flow, then your might get lucky and there won't be a whole lot of other debris to pick out!

Best of luck. (and get 2 impellers.... now!)
 
#26 ·
I have been in contact with sherwood and they told me to go through the warranty process at the marine store. So, I have to send it back and wait. Meanwhile, I will put the old pump back on. It still works, but the seals are starting to leak. They had suggested that I put it on wrong, but there is no way. It only fits one way. If its installed 180 degrees wrong, the block and throttle assembly is in the way of the hoses. If I switched the hoses, it would be painfully obvious. The discharge hose is only long enough to make it to the closest nipple. But, along with persistence, I will have to have patience and jump through their hoops.
 
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