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Old 08-19-2013, 12:02 PM   #41
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OK He just called me back after going and just pulling actual units off the shelf. 8 blade body measures 1.26, 10 blade is 1.32. A difference of .06 is no biggie. Like I thought he thinks the 8 blade will flow more water due to having fewer blades taking up space in a given revolution. He has no idea why a 10 blade impeller would be better than an 8. So I queried him about a 6-nothing.

I'm curious if more blades don't offer more "smoothness" of flow esp at low speeds. Like less pulsation primarily effective on the intake side.

I'm going to order a 10 shortly. I can't see that 2 less blade's volume per revolution will diminish my overall flow enough to notice. I'll report back once installed if I can tell any difference with my application ('83 Mainship III with 200 HP Perkins T6.3544M, primarily 7-8 kt but capable of 12+)
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Old 08-19-2013, 12:18 PM   #42
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Seahorse.

If device has no mfg or patent info, might consider finding shop that does 3 D printing, which can duplicate device. I know I would buy one !
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Old 08-19-2013, 12:44 PM   #43
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Your Perkins should have a Sherwood pump.
Over the years I have tried both Globe & Jabsco in my 6.354 Sherwood pump. Jabsco blades are thicker and more prone to cracking at the base. My Globes (spares) were N/G right out of the box (maybe too old but spares do get old).
The Sherwoods have a much more flexible blade and a small rib on the side of each blade which contacts the pump back and cover plate reducing friction and wear.

I have Jabsco pump on my other boat but use Sherwood impellers in it also.

I don't think the number of blades makes much difference. Reminder: many people fail to apply sealant under the cam when they install it which can lead to priming delays which in turn can lead to shortened impeller life.
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Old 08-19-2013, 12:51 PM   #44
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Please elaborate on "sealant behind cam" comment. What type sealant applied where ? Not sure I have been doing properly.
Thanks.
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Old 08-19-2013, 12:52 PM   #45
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Your Perkins should have a Sherwood pump.
Mine has the same 3193 Jabsco RW Pump many others have asked questions about on their 6 cyl Perkins. It is now obsolete but apparently was used on many Perkins engines
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Old 08-19-2013, 02:15 PM   #46
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Brooksie


Please elaborate on "sealant behind cam" comment. What type sealant applied where ? Not sure I have been doing properly.
Thanks.
You may never have removed your cam, but given the age, maybe someone else has. The cam is the piece which turns the round chamber into an oval; it's held in by a single screw from the outside of the pump. When this is reinstalled or replaced it should have some sealant under it (silicone good) so that air can't be drawn across under it causing slow priming.

Jabsco also makes a reduced volume cam for its pumps so check for this if you are having volume problems

Lots of variables here like cam fit and distance above waterline on pump but this can be a problem.

If Sherwood make an impeller for your Jabsco pump, you will like it better and it will last longer.
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Old 08-19-2013, 02:36 PM   #47
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check out p 171 of http://www.xylemflowcontrol.com/file...ller_Pumps.pdf which suggests your perkins should have a 10 blade 17937-0001. Jabsco 10 blade impeller 17937-0001-P
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Old 08-19-2013, 03:21 PM   #48
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I have somewhat unbelievable news. I just got off the phone with an Engineer (Brian Adams) at Globe. They have NO data about ANY impeller's performance! They don't test any of them. Manufacturers give them a call wanting them to offer a Globe impeller option on a particular application and they manufacture an impeller with the same dimensions as the "stock" impeller! No testing is done! (I'm sure they test for their warranty specs though). The best I could get was that they never advise going to a lesser number on any application. He is supposed to call me back (computers down) when he can look up the drawing specs of the two and give me the difference in blade length-if any. If relatively close, I think I'm going to try a 10 blade. Time will tell.

So far as long term storage-does anyone here do the talc in an airtight ziploc bag method? I found several references to storing the impeller this way. They don't even recommend keeping them in the factory 2 piece vacuum formed package since its not airtight.
Storing for anything more than 6 mos I would consider vacuum bagging slightly (not tight)...I wouldn't bother with talc although I remember old rubber snorkeling gear way always suggested to be stored in talc.

I think for 2 years or less in a ziplock or partial vacuum would be fine then used as the turnover impeller and a new spare purchased.
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Old 08-19-2013, 04:20 PM   #49
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Storing for anything more than 6 mos I would consider vacuum bagging slightly (not tight)...I wouldn't bother with talc although I remember old rubber snorkeling gear way always suggested to be stored in talc.

I think for 2 years or less in a ziplock or partial vacuum would be fine then used as the turnover impeller and a new spare purchased.
The Globes I had trouble with were 2-3 years old but in their original bags when we went to put one to use in Granada, the vanes broke off in my hand. The Sherwoods you can run in your engine for 2-3 years... No Globes for me.
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Old 08-19-2013, 04:22 PM   #50
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I put the SpeedSeal kits on both of my engines this Spring. Last week had no flow from the port engine. Changing the impeller took all of 10 minutes or so. Used the grease that came with the impeller, and lubed the O ring as well. I recommend it highly for ease of use. They also have the teflon spacer that the end plate spins on, which they claim will allow 5 minutes of dry running without eating the impeller. I know it worked for about 2 minutes this year when I accidentally started one on the hard. (oops!) Again, two big thumbs up for this product.
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Old 08-19-2013, 05:05 PM   #51
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Not sure if speed seal saves that much time over a pump that regularly has it's impeller inspected, opened for winterization or replaced (meaning the machine screws come out easily) It only takes me a minute or two to get the machine screws out...it's the impeller that's either easy or the struggle.

The issues some have had with them is what concerned/prevents me from switching.

As a single owner..I'm more likely to plumb my raw water washdown into my cooling system with a quick connect or just full time so I can at least keep idling out of harms way than worry about a minute or two with a pump cover.

I might also keep a spare pump with impeller in it all ready to go...my cats it was worth it...not sur eabout the Lehman direct drive though...sometimes easier to do a few bolts than the impeller.
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Old 08-19-2013, 08:48 PM   #52
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check out p 171 of http://www.xylemflowcontrol.com/file...ller_Pumps.pdf which suggests your perkins should have a 10 blade 17937-0001. Jabsco 10 blade impeller 17937-0001-P
Thanks TTs I really appreciate it. My search skills are lacking!
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Old 08-21-2013, 06:54 AM   #53
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I have found that replacing the tiny screws that are hard to remove

with hex head bolts that can easily be accessed with a hex key , with feel no looking,

is the fastest way to R&R the pump cover.

There cheap so buy a dozen and dont worry , be happy , when one gets away.
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