possible raw water pump failure

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possible raw water pump failure

Started my engine on my boat today, and didn't see any water coming out of exhaust. I checked raw water strainer and thru hull, and didn't see an issue. Impeller is changed every year, so didn't feel that could be the cause. I pulled the engine cover and found a very rusted out raw water pump housing. Highly suspect this is my cause. I have a 2004 C36MKII with the M35B. Considering replacing with the Oberdorfer N202M-908. Wondering if anyone else has done this, and if I have the correct part #?

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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I replaced the Sherwood with an Oberdorfer N202M-16. A slight modification to the mounting base and one of the nipples was required. There is a lot of info on this site.

Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

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Additionally, if pump failure is due impeller fins breaking away, be sure to remove that debris from your heat exchanger.

Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

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I use a Oberdorfer N202M-908 on our Mk2 with a M35B engine.  It’s an adequate bolt on replacement, and believe that it’s suitable for many other Universal diesels.   The N202M-16 is the same pump with a different mount.    The N202M-908 is a bolt on replacement.

I’m in the minority but I’ve always felt that the Sherwood G908 is a better pump. There is nothing wrong with having your old pump properly rebuilt.  That said, by the looks of your pump body the seal has been leaking for a long time (years).    This could lead to a situation where it’s not rebuildable (I suspect this to be the case).

Search the forum and I’d be surprised if you don’t find a tutorial or photo essay of this common change over.   The readers digest version is that it is bolt up but requires modification  of the inlet/outlet 90’s.    The previous owners of our boat installed our Oby pump and provided a complete spare.  These were piped up by the vendor, Cardinal Pumps and Ill include a photo of the spare.

Cardinals solution was a little over the top.    The Sherwood G908 in/out 90’s are too close together for the Oberdorfer.  This prevents the second 90 from rotating in place.   Most owners just shorten one 90 until it clears.

 

Paul brings up a good point.   It’s important to find out why your old pump failed.  The Sherwood G908 has its problems but they usually pump.   The 2 main causes of not pumping (due to pump failure) are the pump face is worn allowing raw water to bypass the impeller, or the impeller is so damaged that most of the vanes are destroyed.    There are additional causes, some quite extreme, but these are the most common.   If the pump face is scored the part is quite expensive, making the rebuild parts alone about the same as an Oberdorfer pump.   If the impeller is destroyed you need to find the pieces or they will reduce flow through your raw water heat exchanger, leading to overheating.   If the pump face and impeller are good you may have a larger issue.   

Ray & Janice Taylor
"Mizu"
Hood River, Ore.
#2113 2002 TM
 

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Great information everyone. Thanks. Headed to boat right now to take apart. Being doing quite a bit of research and i am concerned about my engine possibly running hotter with the Oberdorfer. I am in San Diego, and the water is fairly warm.

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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Blair, if you are a DYI with tools, you can easily modify the N202M-16 version base and save $200.00. I converted to Oberdorfer years ago and I am very happy with its service. I also replaced the seals once after 230 hours of use.
You can find content and photos on my website and album on my signature below.
Haro.

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I agree with Haro, same pump, easily modified base.  

As you have read the Oberdorfer does not pump as much as the Sherwood which can lead to overheating.   It's been my experience that the Oby is fine for our application if the other components of your cooling system are in good shape.   I have no overheating problems in water warmer than San Diego.   

Ray & Janice Taylor
"Mizu"
Hood River, Ore.
#2113 2002 TM
 

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Ok, got my replacement pump. The impeller is already installed in it. Should I shoot a little dish soap in the ports so I don't have a dry start?

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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Wow! This is ugly!

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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Impeller looks good.

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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The new pump.

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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Successfully installed, but I have water dripping out of cover on front at bottom screw.
removed cover to see if O ring was there and properly seated. It was. Now what?

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

Ken Krawford
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In the past those pumps came with an O-ring AND a paper gasket.  You only need one.  If you use both the pump face will leak.

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My understanding is the paper gasket is for where the pump mounts to the engine. It is a circular gasket, and only location that it fits.
The pump comes with impeller and o ring already installed. I took the front cover off, and there was white grease on everything. I would imagine that this is mainly supposed to go on impeller, so you don't have a dry start. I don't know if this is causing the leak.

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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Blair,

The bottom screw of the Oberdorfer face plate should be installed with locktite to prevent leaks.  This video shows the procedure around 9 minutes.  This may be the cause of your leak.

https://www.youtube.com/watch?v=2cOec7fNM_A

The Impeller lubricant that Technician uses in this video is Jabsco Impeller lube. You should see or feel a waxy residue from this lube.   This is the only lubricant they recommend although many use lots of different lubes.   Sherwood recommends soapy water or silicone.  

Additionally I spoke with the pump technicians at Oberdorfer earlier this year.  At that time the only lubricant they recommend was Jabsco Impeller Lubricant.  It’s is a clear honey colored lube.  It seems odd that your pump has white grease, also the impeller and shaft are not installed when the pump is shipped.  This prevents the impeller from taking a set during storage.

Ray & Janice Taylor
"Mizu"
Hood River, Ore.
#2113 2002 TM
 

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Blair, I replaced the original 4 screws with allenhead screws. To prevent leaks I apply ample amount of lanocoat then tightening the screws. Run the engine withe cover on so it becomes warm then tighten screws more.
Haro.
 

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I would not suggest using loctite on the screw or it will be difficult to impossible to remove in the future.
The bottom line is there should be no leak if everything is made correctly. Check that the O ring is not damaged (no nicks or cuts) as well as the grove that it sits in is not damaged (no metal burrs). Also check the plate flatness with a metal straightedge (there should be no visible scratches and no gaps between the plate and straight edge).  Did they supply a proper diameter O ring? 10%-15% of its thickness should be sitting above the groove when its seated to create an effective seal.

Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

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Thanks again for everyone's input.
This is pretty disappointing.
I don't see any visual reason for the leak. I am going to reach out to where I bought the pump, and request a new O ring.

I may have other issues as well.
There does not appear to be any water coming out the exhaust at idle.
When I raise the engine speed, water starts to come out. I went out for a short motor, and engine temp never went above 165.
I see other boats at idle in my marina, and water is coming out exhaust.
Looks like I have another issue to address.
I wonder if it is ok to take boat out like this?

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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Blair-
Isn't the o-ring located inboard of the four plate screws? Refresh my memory on that point. If so, and you are getting an apparent leak through one of the screws, it's really not the screw, it's the o-ring not sealing correctly. If it's not sealing, then its probably also allowing air to be sucked into the pump and therefore the pump would be loosing suction until you overcome it with increased RPM. You should be seeing water flow out the exhaust at engine idle. Again, if the face plate is slightly bowed and not perfectly flat, there is damage to the o-ring grove or o-ring itself, the pump will leak and suction will be compromised. 

Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

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Paul,
Yes, you are correct on the o-ring location.
When you first suggested checking o-ring, I did pull it apart and gave it a visual.
Maybe I didn't look close enough? I also did not check cover with a straight edge to see if it is flat.
I am waiting for my replacement o-ring, and will check that cover is flat at that time.
Do you feel it is ok for me to take my boat out in this condition?
I have a big group showing up on the 4th, but don't want to risk damaging my engine.
Maybe if I just keep rpm above idle?
Thanks again to all for this valuable input.

Blair White
2004 C36 MKII # 2169 "Dash"
Pacific Beach, CA

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Based on your test run experience, it's probably ok to use the boat. Just keep an eye on the temp gauge and be ready with the anchor if a cool down is needed. You also might experiment with some silicone grease on the water pump impeller and o-ring and see if that alleviates the issue for the time being.

Other root causes for poor water flow can be salt/mineral  buildup in the exhaust elbow, intake flow restriction, (ie seaweed in the filter basket), worn impeller or pump casting wear from the impeller (unlikely with your new pump), heat exchanger corrosion/clogging. I've experienced most at one time or another over my many years on the water.

Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

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