Sherwood Raw Water Pump - Is it supposed to weep?

[Bob4203]

I was running my Universal M-18 equipped with the Sherwood Raw Water pump this past weekend, checking all my hoses, clamps and other fittings readying for the spring. I noticed a slight drip, drip, drip, coming from under the Sherwood Raw Water pump impellor housing (about an 1/8 " hole). I was not sure if this was for pressure relief which helps from keeping that light paper gasket on the face plate from blowing.

I saw the schematic of the pump and noticed a 1/8" NPT brass screw in "drain plug" but I failed to feel for any other plug after I turned the engine off.

Do the raw water pumps, specifically the Sherwood weep water? Or do I indeed need to buy the replacement plug?

Thanks
Bob
1988 Catalina 30 Mark II

 

[Stu Jackson]

When that happens, it is time to replace the seals, there are two, one for water and one for oil. Check that pump diagram again.

Here's how to rebuild a pump, in this case it's an Oberdorfer, but yours is similar. Either rebuild or buy a new pump.

Oberdorfer Pump Rebuild 101 - http://c34.org/bbs/index.php/topic,6766.0.html

You NEED to do it, and soon.

http://c34.org/bbs/index.php/topic,5078.msg31322.html#msg31322

I recommend you also read the links within those links, lotsa good info there. You could also consider buying an Oberdorfer replacement pump, it's better built than the Sherwood. Source is DEPCO.

 

[Bob4203]

Thanks Stu,

I replaced the impellor last year as well as the front seal. The slow drip is pure water coming directly from the intake strainer (lake water). No oil sheen noted. Why would it be time to replace the seals? The hole in the bottom of the body would be below the impellor (slightly off center) in the water housing.

I could check and see if the hole is threaded (mirror and flashlight needed for that), but I do not believe the pump requires resealing. The engine only has 548 hours on it! I just want to know if these pumps have a weep hole for water pressure relief?

Thanks

Bob

 

[JK_Boston_Catalina310]

Bob,

You might also want to consider dumping the Sherwood. I did it last year and would never go back. Here is a post on the subject (http://forums.sbo.sailboatowners.com/showthread.php?t=139566). I had to do some modifications but I don't think you would for your motor, it should just bolt on.

Jesse

 

[Bob4203]

No, I do not believe that I have to rebuild or replace my Sherwood raw water pump just yet. I did not use the engine for a long time last year and the impeller deteriorated and was replaced. It was no big deal aside from chasing small pieces down to the heat exchanger. Why a paper thin, paper gasket on the outer cover plate surprised me!

Okay back to the question: Do Water Pumps Weep by Design? :dance:

Thanks
Bob

 

[Stu Jackson]

Thanks Stu,

I replaced the impellor last year as well as the front seal. The slow drip is pure water coming directly from the intake strainer (lake water). No oil sheen noted. Why would it be time to replace the seals? The hole in the bottom of the body would be below the impellor (slightly off center) in the water housing.

I could check and see if the hole is threaded (mirror and flashlight needed for that), but I do not believe the pump requires resealing. The engine only has 548 hours on it! I just want to know if these pumps have a weep hole for water pressure relief?

Bob,

I don't understand the "slow drip is pure water coming directly from the intake strainer (lake water)..." I thought the leak was from the pump's own weep hole. Can you explain this?

Why would it be time to replace the seals? ...but I do not believe the pump requires resealing. If, indeed, the water is coming from the pump's weep hole, it means one of the two seals failed, regardless of how long or short ago you replaced them. The link in JK's post pretty well describes the issues with Sherwood pumps, and Capt Ron calls them "crap" which is, compared to the Oberdorfer's, pretty much the consensus of the group, both here and in our C34 forums and the C34 Tech wiki. Please try that link and get back to us.

Good luck.

 

[Stu Jackson]

No, I do not believe that I have to rebuild or replace my Sherwood raw water pump just yet. I did not use the engine for a long time last year and the impeller deteriorated and was replaced. It was no big deal aside from chasing small pieces down to the heat exchanger. Why a paper thin, paper gasket on the outer cover plate surprised me!

Okay back to the question: Do Water Pumps Weep by Design? :dance:

Thanks
Bob

Bob, yes, they do. That's the whole concept of weep holes. The impeller has nothing to do with the seals. The impeller pumps the water, the seals keep the oil and water apart.

See my previous comments.

 

[Bob4203]

Stu,
You then answered my question. Yes, they do weep.

When I see an exploded view of the Sherwood pump, there is a drain hole that takes an 1/8" NPT brass screw in plug. That fills in a small hole. This is called the "drain hole" with associated "drain plug". Obviously, it just drains the water in the housing that contains the impeller, which to me would be unnecessary unless water pressure when the engine accelerates must build up enough that a relief hole or discharge hole for the raw water must escape. I might have been looking at that hole! I did not have a mirror and flashlight to be able to determine if the hole was threaded. If threaded then obviously the plug came out. I was not aware that a drain hole existed. All I know is that when the engine was running I could see droplets of water coming from this hole. It was not associated with he internal seal as suggested as no oil was observed. I sail in a lake and what was coming out the hole was lake water; clear and fresh.

Thanks
_/)

So, if indeed these pumps do have a weep hole to relieve the pressure then all I have to do next time I am up on the boat is feel for the plug under the pump housing. If I find the plug, hey I have a weep hole! If not, I will have to buy a plug.

 

[Stu Jackson]

So, if indeed these pumps do have a weep hole to relieve the pressure then all I have to do next time I am up on the boat is feel for the plug under the pump housing. If I find the plug, hey I have a weep hole! If not, I will have to buy a plug.

Bob, the long first part of your last post I didn't copy here, and you seem to be getting it. It's NOT a pressure relief hole, it needs to be closed tight all the time.

The weep hole and the drain plug are two separate things. In this link

http://www.marinedieseldirect.com/c...ervice=200151&printoperators=200157&comment1=

The drain plug is Item 13. That seems to be what you are mentioning, correct? If so, you simply need a new plug, which has nothing to do with the weep holes and the seals.

Happy hunting.

 

[Bob4203]

Actually, I was hoping that someone who had to remove the Sherwood pump for repair, replacement or otherwise would provide the answer. I will be checking it out further to determine if this small hole in the housing is the drain hole and will therefore require that plug in the schematic. If however I do find that a plug is found when I look over the unit closer, then the small "weep" hole must be just that, a "weep" hole. Crazy, hey?

Bob

 

[Anonymous 121765]

I agree with JK

I also had a Sh**twood pump, two actually.

I believe they're designed to fail.

If you compare them to an Oberdorpher pump, they have a third more parts.
And what's with the half clips?

First pump lasted a year and a half on a new engine. Second one lasted less than that.

If you get tired of messing with an inferior pump, try the Ober, it's interchangeable.

CR

 

[Bob4203]

Hey Cap,

Appreciate the feedback. If I were to take the boat out of the Army Corp impoundment we call Lake Lanier, I am sure I would pick up an Oberdorfer as a replacement. So far with over 500 hours on the engine and circulating fresh lake water I only had to replace the impellor once and it was because the engine sat idle for over many months. The fins dried up and became brittle. Thus far no oil seal breakthru, binding, shaft failure, etc, etc on the Sherwood.

I am going up to my boat this weekend, will feel around for the drain plug on the impellor body and determine if that hole I saw with the dripping water was the drain with a missing plug. If so, I will correct it. If however, I do observe that the drain plug is in and the "other" hole is weeping water then I will asssume this is part of the design and that I can live with as it has caused no harm in the last 500+ hours of engine operation so far.

Bob

 

[Stu Jackson]

One last time

Bob, the pump should NOT weep anywhere. There are, or should be, no holes for water to drip out of the impeller portion, and the ONLY other place it could weep from is, well, the weep hole. Take another look at the diagram and my earlier comments. Whether or not you're in salt water, drips from the pump can have a catastrophic impact on your forward starboard engine mount and the oil pan, neither one is good for your engine (from my earlier links).

Good luck.

 

[Bob4203]

Stu,

The first thing I did when I got home was download the schematic of the Sherwood pump where I too noticed the drain hole and plug, but no second hole in the housing diagram. I sent MarineDiesel an email inquiring about a second hole as well, but nothing came back so far. I just wanted someone to pull the impellor housing to check and see if one or two holese were present. It does not make sense to have a weep hole as the force of water flow would literally make a continuous stream come out. Your right about the water dripping on the block above the oil pan and gasket and running down the mount. Does not make sense!! So I will solve the mystery this weekend and determine if indeed the drain plug came out and replace as necessary. If the shaft bearing failed I would see oil coming from behind the impellor housing through the gasket between the engine and pump unit. For now its just fresh water coming in from my thru hull and picked up into the impellor housing...........as for an immediate replacement? I will pay closer attention to this Sherwood as cautioned by several responders.

Thanks

Bob

 

[Stu Jackson]

If the shaft bearing failed I would see oil coming from behind the impellor housing through the gasket between the engine and pump unit. For now its just fresh water coming in from my thru hull and picked up into the impellor housing...........as for an immediate replacement? I will pay closer attention to this Sherwood as cautioned by several responders.

Bob, Good to hear. The shaft bearing is also not the "issue", recall, there are two seals, the water seal and the oil seal. One could well fail before the other. It works BOTH ways. If the water seal fails, you get water through the weep hole. Then the ONLY thing stopping water from getting into your engine is the oil seal, which is designed to keep the oil from getting out. I still don't understand "the fresh water coming in through my thru hull" part, sorry.

Sometimes one doesn't hear back via email. I'd call the DEPCO pump guys in FL.

Good luck.

 

[Bob4203]

Thanks Stu,

The DEPCO website is very impressive, but I could not find a blow-up schematic of my Sherwood pump to locate a second hole in the housing. I will just have to wait and see when I get back to my boat.

I will let everyone following this know via this thread what I found to help other M-18 or Sherwood Raw Water pump owners. Its the drain hole needing a plug or I am in trouble!

Bob