Impeller Installation - H386

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Jeff Bacon

Jeff Bacon

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May 5, 2004
181
Hunter 386 Little River, SC
Hi All:

This is one of those Theory vs Practice questions. I know how to change an impeller, but have never done it before.

I have a 2003 h386 with a 3JH3E Yanmar. I have the old impeller out, and the new one ready to go in, but I realized I do not know which way to "turn" the impeller to get the blades going in the right direction. I have attached a diagram of two "impellers" (I drew them on Paint). Can anyone tell me which direction I should turn the impeller on installation to get the proper twist ?

This assumes I am at the back of the engine at the transmission and looking forward.

Thanks !!

Jeff
 

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Ron20324

Ron20324

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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Snotter said:
Don't worry about it; it will correct itself.
Click to expand
That's true, but why not do it right the first time? Actually, if you know the crankshaft rotation, you can figure out the impeller rotation if it's belt-driven. Have someone click on the starter without starting the engine and watch the rotation. Once you do figure it out, mark the cover with an arrow and a marker pen or paint.
 
Ed Schenck

Ed Schenck

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Jun 2, 2004
5,802
Hunter 37-cutter, '79 41 23' 30"N 82 33' 20"W--------Huron, OH
True, it will correct without damage. But being anal you want to insert it "just right". :)
Look at the engine as you are installing the impeller(assuming RH drive). Visualize the prop turning counterclockwise from this end. Shaft and alternator also turning CCW. So is the shaft for the waterpump turning CCW. Thus your "left hand twist" picture. A little petroleum jelly on the vanes will help the install and lubricate until the water gets there.
 
John T1594

John T1594

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Jun 4, 2004
834
Hunter 340 Forked River, NJ
Impeller

I just changed out the raw water impeller on my Yanmar 3GM30F. I had marked the direction of rotation so it was easy to put the impeller in the correct way.
Anyway, for the first time, the impeller came with an instruction pamphlet and a small tube of Yanmar Impeller Lubricant. The lube is glycerine and the manual says not to use any petroleum-based lube on the impeller vanes as this will destroy them.
 
Tim R.

Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
It does not matter. Just install it and be done with it. If it is that important to you then mark the housing the next time you change it or remove the cover after running the engine this time and mark it.
 
N

navigator97

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May 24, 2004
470
Hunter 33.5 Portsmouth, RI
Jeff, To ease the installation, after you figure out the direction, is to "gather" the vanes with a cable tie to get the insertion started. When is about half way in, cut the cable tie and push in the rest of the way.
 
Rich Stidger

Rich Stidger

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Feb 10, 2004
4,235
Hunter 40.5 Warwick, RI
The water always flows around the long path, in-to-out

Regardless of how your pump is orientated, just remember that the water flows from the inlet to the outlet along the longest path. In the picture below, the inlet happens to be on the right so the water flows clockwise through the pump. This means that the impeller also turns clockwise looking at the cover plate, and the vanes would have a right-hand twist referencing Jeff's sketch.

As long as you know which is the inlet and outlet, it is easy to figure out which way it turns. These pumps are symmetrical, they can run in either direction depending upon application.
 

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Berndahle

Berndahle

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Aug 31, 2009
70
Hunter 36 Herrington Harbour North, MD
Don't rely on which direction the old impeller vanes were when you took it out. Sometimes when you turn off the engine it may turn backwards a fraction of a rotation and flip your vanes in the other direction. Best to figure out which direction the water should flow but as most said here, it doesn't really matter because it will correct itself.
 
All U Get

All U Get

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Oct 2, 2008
3,811
Pearson/ 530 Strafford, NH
Hi all,
Would Starbrite's White Teflon lubricant be good for greasing the impeller?
All U Get
 
S

Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Good luck! These impellers are very difficult to install to begin with. They are nothing like the GM engines.

Just get it on the shaft/key and you will be good to go.

PS: I do not know you can figure out which way the water flows very easy on the JH motors either.
 
Snotter

Snotter

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Sep 25, 2008
615
Morgan 415 Out Island Rogersville, AL
All U Get said:
Hi all,
Would Starbrite's White Teflon lubricant be good for greasing the impeller?
All U Get
Click to expand
Squirt some dishwashing soap in to lubricate the first few seconds when there isn't any water in the pump; however, running it dry for a minute or so at low rpm won't distroy it.
 
C

Capt Mike

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Oct 31, 2008
30
Hunter 386 Point Breeze,NY
Jeff, Just changed mine last week, the same boat 03' 386. I had to recplace the alternator belt so I just removed the alternator from the engine, gave me a lot more room to work taking the cover plate off. Took my engine cover completely off and set it by the galley, much more room to work ! The old one was a little hard getting loose from the shaft, I think it was the original impeller. Used a small pair of needle nose vice grips, clamped on one blade tapped a little with small mallet, then went to the other side of the impeller clamped on another blade before it broke loose. I remembered the side that came out first, the blades still had a slight curve in the direction it ran. A mechanic told me to lube the new one with only Glycerine...Also replace the "O" ring. As they say it really dosen't matter which way the blades go, if you look in the housing it's tappered on each side to right the blades for the direction it turns. One last note, I went to the hardware store and got four stainless cap screws and the allen wrench to go with them, makes it a lot easier to install them..Hope this helps. Also one of my blades was broke completly of the impeller, it was lodged in the upper part of the impeller housing-mechanic said I was lucky to find it!!! Hope this helps,Good Luck,Mike
 
M

MitchM

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Jan 20, 2005
1,031
Nauticat 321 pilothouse 32 Erie PA
jabsco makes a new style impeller for the yan 3JH series that has a cleverly threaded center hub. makes it quite easy to get the impellers out without using needle noses. unfortunately some dealers will try to use up their supplies of the old style impeller instead of sell you the new ones...or worse yet not even know t here is new style available...
 
Prime Time

Prime Time

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Sep 25, 2008
544
Bristol 43.3 Perth Amboy
Impeller Direction

Take the cover off the water pump and have someone hit the starter.
Watch the direction of rotation.
Then mark the cover with an sharpe.
 
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