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Hitchin' a ride
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Discussion Starter · #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?
 

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Telstar 28
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Teflon tape please... not polyurethane caulk... Teflon is far more chemical resistant IIRC...
 

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Telstar 28
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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...
 

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Jolly Codger
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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.
 

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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... ;)
 

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Senior Member
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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.
 

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Hitchin' a ride
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Discussion Starter · #10 ·
I think the HE zinc should be ok by itself. It has a 1/4 inch of fine thread and feels very tight without the tape. Thanks guys.
 

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You could carefully run a miniscule bead of high-heat gasketing around the top of the threads, or even the top of the zinc screw hole. If the zinc has several threads in direct contact with the metal, it should work. But if you goop over the seam, that may lessen the dripping and achieve your goal.
 

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Hitchin' a ride
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3,191 Posts
Discussion Starter · #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.
 

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I know it's a new pump but check the impeller. As for the hoses if 5/8 was on before it should be going back on I would think. Ambient temperature I would guess could effect how a hose slids on a off? Measure the OD of the fitting?
 

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Hitchin' a ride
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Discussion Starter · #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.
 

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Telstar 28
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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.
 

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Hitchin' a ride
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3,191 Posts
Discussion Starter · #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:
 

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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.....
 

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Hitchin' a ride
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3,191 Posts
Discussion Starter · #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.
 

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Hitchin' a ride
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3,191 Posts
Discussion Starter · #20 · (Edited)
Oooo. Learn something new everyday!

Well, wrong again. I took the elbows off and turned the shaft and it does rotate easily both ways. Looking into the holes I can see that only one of the blades is torn off.
 
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