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Old 03-21-2023, 06:57 PM   #1
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Raw Water Hose Replacement

I decided to see if I could find the missing fin from my impeller that I noticed was AOL when I put the boat up for the winter. My raw water pump is connected to the engine oil cooler by two short lengths of hose with an aluminum(?) tube in the middle. Mine had obviously been there for a while, and I eventually resorted to a heat gun and slip lock plyers to loosen the hoses enough on the tube that I could get the assembly apart (destroying the hoses in the process). This seems to be a pretty common setup on Leman engines and I was wondering if other people have difficulty getting the setup apart to hunt down impeller bits and pieces?

I was thinking it might make sense to simply ditch the solid tube and put one continuous piece of hose between the raw water pump and the cooler. The way I see it that would make it easier to bend and flex the hose to remove it when needed. Does anyone know a reason not to do this. It would also have the advantage of reducing the number of hose connections from four down to two.

I have seen some people suggest putting a "Y" strainer in this section of hose to catch impeller bits before they get to the oil cooler. Is there any reason not to add a strainer to the system?

My impeller chunk was sitting right there waiting for me to retrieve it. Looking into the cooler is seems that it would be pretty hard for any bits to make it any further into the system. Am I right in that thought?

Looking forward to hearing what the engine gurus have to say!
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Old 03-21-2023, 09:23 PM   #2
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No Guru here but I too have thought about eliminating the pipe. But my assumption it must be there for a reason. Why else did they add it? Perhaps hose close to the block would not be safe or hold out thus the pipe?Probably Brian at American Diesel would be the one to consult.
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Old 03-21-2023, 10:09 PM   #3
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Absolutely consult with Brian before doing any mods and see what his take is. I donít see any problem but I am not an engine guru, but Brian is.
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Old 03-21-2023, 11:03 PM   #4
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Originally Posted by R. Bush View Post
I decided to see if I could find the missing fin from my impeller that I noticed was AOL when I put the boat up for the winter. My raw water pump is connected to the engine oil cooler by two short lengths of hose with an aluminum(?) tube in the middle. Mine had obviously been there for a while, and I eventually resorted to a heat gun and slip lock plyers to loosen the hoses enough on the tube that I could get the assembly apart (destroying the hoses in the process). This seems to be a pretty common setup on Leman engines and I was wondering if other people have difficulty getting the setup apart to hunt down impeller bits and pieces?

I was thinking it might make sense to simply ditch the solid tube and put one continuous piece of hose between the raw water pump and the cooler. The way I see it that would make it easier to bend and flex the hose to remove it when needed. Does anyone know a reason not to do this. It would also have the advantage of reducing the number of hose connections from four down to two.

I have seen some people suggest putting a "Y" strainer in this section of hose to catch impeller bits before they get to the oil cooler. Is there any reason not to add a strainer to the system?

My impeller chunk was sitting right there waiting for me to retrieve it. Looking into the cooler is seems that it would be pretty hard for any bits to make it any further into the system. Am I right in that thought?

Looking forward to hearing what the engine gurus have to say!
Would someone please explain to me how to just highlight and answer the paragraph that I want to address, which is about the "Y" strainer? Question 1! I know I have read why it would be helpful to isolate impeller parts before they go any further, but I now can't visualize how a "Y" would work. Question 2! So those are the questions I want to get answered, but cannot figure out how to streamline the question to the specific quote.
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Old 03-22-2023, 07:08 AM   #5
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Originally Posted by R. Bush View Post
I decided to see if I could find the missing fin from my impeller that I noticed was AOL when I put the boat up for the winter. My raw water pump is connected to the engine oil cooler by two short lengths of hose with an aluminum(?) tube in the middle. Mine had obviously been there for a while, and I eventually resorted to a heat gun and slip lock plyers to loosen the hoses enough on the tube that I could get the assembly apart (destroying the hoses in the process). This seems to be a pretty common setup on Leman engines and I was wondering if other people have difficulty getting the setup apart to hunt down impeller bits and pieces?



I was thinking it might make sense to simply ditch the solid tube and put one continuous piece of hose between the raw water pump and the cooler. The way I see it that would make it easier to bend and flex the hose to remove it when needed. Does anyone know a reason not to do this. It would also have the advantage of reducing the number of hose connections from four down to two.



I have seen some people suggest putting a "Y" strainer in this section of hose to catch impeller bits before they get to the oil cooler. Is there any reason not to add a strainer to the system?



My impeller chunk was sitting right there waiting for me to retrieve it. Looking into the cooler is seems that it would be pretty hard for any bits to make it any further into the system. Am I right in that thought?



Looking forward to hearing what the engine gurus have to say!
Pictures would help. As for eliminating a metal tube, in my opinion, there is absoulutely no reason why this cannot be safely done. The circuit is simple low pressure. As long as the hose does not rub against anything, an intervening metal tube is not necessary. As to why the system was designed that way, who knows? I have attached a picture of my Lehman 120. Notice the blue silicone hose. That hose goes from the header tank (7 psi cap) to the heat exchanger. There used to be steel pipe in between. I think it was there because the clearance behind the injector pump is tight, but silicone hose is thinner walled so there is no danger of rub-through. Yes, that hose is sufficiently-rated rated for pressure.Click image for larger version

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Old 03-22-2023, 08:05 AM   #6
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Greetings,
Mr. RB. Perhaps the length of steel tube is to eliminate eventual sag of a long rubber tube run.
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Old 03-22-2023, 08:56 AM   #7
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A good quality bronze strainer would be fine in my opinion. I canít imagine why not anyway.
I have a lot of experience with them in different applications, and I was exactly thinking I might add one after the raw water pump too.
Something like this one, it traps anything in the screen and you can clean it out in place.
https://www.grainger.com/product/APO...-Bronze-40D872
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Old 03-22-2023, 11:08 AM   #8
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Greetings,
Mr. RB. Perhaps the length of steel tube is to eliminate eventual sag of a long rubber tube run.
The total length of the run is only 12" with a slight downward inclination. Surely a piece of wire reinforced hose should be able to handle that without sagging or vibration being an issue.
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Old 03-22-2023, 01:37 PM   #9
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Thanks to everyone who posted a reply. I took the advice of the group and sent my question to the ever helpful Brian at American Diesel. As an FYI here is his response:

A) Is there any reason I shouldn't replace the two small pieces of hose and the metal tube connecting the raw water pump to the engine oil cooler on my SP135 with a single piece of high quality hose? It would make it a lot easier to remove that section to look for any impeller bits that may have gotten loose from the raw water pump and gotten into the system. No reason why a wire-reinforced hose wouldn't be a great way of connecting the raw water pump to the oil cooler.

What about adding a "y" type strainer to that hose to catch the bits before they get into the oil cooler in the first place? No need, your engine oil cooler will catch the impeller blades that manage to break free. Our recommendation is to install a "water flow alarm" sensor on your exhaust elbow, which will let you know if the water flow is impeded.
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Old 03-22-2023, 05:19 PM   #10
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Another reason for metal pipe in a coolant line my be to prevent the hose from collapsing if it is on a low pressure or suction side of a water pump.

A wire reinforced hose replacing a metal pipe would prevent that negative event.
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Old 03-22-2023, 06:26 PM   #11
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Greetings,
Mr. A. Valid point but on a Lehman the pipe is on the pressure side. It's in the hose from the water pump to the heat exchanger.
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Old 03-22-2023, 07:22 PM   #12
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I removed that bit of steel pipe from both my Ford Lehman 120s. No steel reinforced hoses required because this hose would NEVER be under suction. Sag? Hardly any and so what if it does? If you are anal about it you can add a couple of zip ties along the way to prevent sag, but again, so what?
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Old 03-22-2023, 07:25 PM   #13
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Quote:
Originally Posted by R. Bush View Post
Thanks to everyone who posted a reply. I took the advice of the group and sent my question to the ever helpful Brian at American Diesel. As an FYI here is his response:



A) Is there any reason I shouldn't replace the two small pieces of hose and the metal tube connecting the raw water pump to the engine oil cooler on my SP135 with a single piece of high quality hose? It would make it a lot easier to remove that section to look for any impeller bits that may have gotten loose from the raw water pump and gotten into the system. No reason why a wire-reinforced hose wouldn't be a great way of connecting the raw water pump to the oil cooler.



What about adding a "y" type strainer to that hose to catch the bits before they get into the oil cooler in the first place? No need, your engine oil cooler will catch the impeller blades that manage to break free. Our recommendation is to install a "water flow alarm" sensor on your exhaust elbow, which will let you know if the water flow is impeded.
Borel is fhe brand fo use.
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Old 03-22-2023, 07:26 PM   #14
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I removed that bit of steel pipe from both my Ford Lehman 120s. No steel reinforced hoses required because this hose would NEVER be under suction. Sag? Hardly any and so what if it does? If you are anal about it you can add a couple of zip ties along the way to prevent sag, but again, so what?
Rich, exactly. That has been my experience.
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Old 03-22-2023, 08:52 PM   #15
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Greetings,
Mr. A. Valid point but on a Lehman the pipe is on the pressure side. It's in the hose from the water pump to the heat exchanger.
Thanks for the education. I have a lot to learn.

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