How to Change Impellers in 8.1's with Pictures

Hampton

Air Defense Dept
TECHNICAL Contributor
Nov 26, 2006
7,628
Panama City, Fl
Boat Info
2008 44 Sedan Bridge
Engines
Cummins QSC-500's
Straight Drives
1) Close Sea Cocks.

2) Remove Serpentine Belt: Note free play, then loosen alternator tensioning assembly as follows: Loosen the nut nearest the center of the engine and spin it over about and inch. Loosen the bolt at the end about an inch and allow the alternator to swing inward to loosen tension on the belt. If it doesn't swing, loosen the bolt that acts as a hinge at the top of the alt. Swing alt in and slide belt toward you off of one of the pulleys that doesn't have ridges. Keep track of direction of belt by laying it down without turning it over.

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Once the belt is off, remove the 2 nuts and 1 bolt that hold the pulley bracket and raw water pump (impeller pump). The bottom 2 are of one size, are nuts, and secure the pump. The top one is a bolt of a slightly different size and only holds the pulley bracket.

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Remove the pulley bracket and 2 pulleys and set aside.

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Reach behind the port side of the pump and remove the two, blue plastic wing-bolt style plugs and set aside. Keep track of the O-rings. Remove the two hose brackets off of the two hoses. The bottom is outgoing and is somewhat plyable. The top one is red and is the incoming, vacuum hose (withstands vacuum from the pump). It is short and not very plyable. Remove the wire harness to the sensor from the back of the pump. There is a small tab which extends the entire length of the black plastic housing. Lift the tab and separate the two halves of the sensor housing to free the wiring. It is a lift tab.

Try to work the hoses loose by the least aggressive method possible. Try using your hands, then perhaps and awl, and in the worst case, a big ass screwdriver like me.

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Once the hoses are loosened up, the pump should, theoretically, pull off straight. In reality, it won't. Put your right hand behind the top, right side of the pump and begin to pull it off of the bolts and away from the hoses. Work it up and down and back and forth. As you begin to get it out away from the block, put a large socket piece between the pump and the block from the top right to hold them apart at the top. Then, pull the pulley (bottom of pump) away working side to side. Finally, give up on brut force and work a large screwdriver between the left side of the pump and the block. Make sure you do not put any pressure on any fuel lines, sensors, or other sensitive parts. Pry the pump free of the hoses.

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Remove the 10mm nuts from the back of the pump. There are 3 lengths. 2 long ones hold the bracket. Several short ones hold the pump together. 1 medium one holds the base of the bracket to the side of the pump. Don't forget this one.

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Lay pump on pulley and remove other half. Observe rotation of Impeller.

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Check for wear of the housing. If it's worn, replace it - the labor is the hard part, not the cost of an entire pump.

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Take the impeller out. I used to flat screwdrivers on opposite sides prying it out at the same time. Set it down in the same position to reference spin direction. Begin to insert new impeller while bending vanes over as you go around the circumference to get it started into the pump. Once you get it started, spin the pump using the pulley as a base plate and push down on the impeller to get it to go in. (I didn't notice until I got home that in the video below the pulley was slipping on the towel so you can't see the rotation of the impeller, but you get the idea.) Lube the impeller with soap or something.



Put the new O-ring into the slot. I "Glued" mine in 2 1/2 years ago with grease to get it to stay. It showed zero wear. This time, I just held it in place while slowly sliding the other half of the pump in place to keep the O-ring from coming out of the groove. Once I had it in place, I looked around the side of the pump to make sure it matched perfectly to ensure the O-ring wasn't crimped. Put your favorite product on the bolts and replace them. Put your favorite product on the hose nipples to make them come off next time. Push pump back in place while aligning hoses. Bolt on with pulley bracket in place. Replace hose clamps carefully - in place and straight. Replace sensor wiring plug. Replace blue, plastic wing bolts.

Put serpentine belt back on the way it came off, sliding it on over a smooth pulley as the last part. Use other engine or guide sticker on engine as a guide. Re-tighten the bolt on the end. Re-tighten the securing nut. Re-tighten the hinge bolt (I still have to do that on the port side - I forgot). Tighten the alternator adjustment until you can just displace the longest stretch of the belt 1/4" with pressure from your thumb.

For port engine in a 2003 1/2 - 2008 340DA, move the muffler out of the way. Remove 4 base screws. Remove a couple of the exhaust hoses strategically to allow the unit to be moved aft without taking it all apart.

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OPEN THE THROUGH HULLS!

Then, loosen one of the Blue Plastic Wing Bolt Plugs until water flows out to prime the lines. If you open the "Out" side port (where water flows out of the pump) and get some water, then the pump should be primed and good to go. If no water comes to that one, then open the other to get very close to a good prime. Shut those also.


Today, this took a total of 3 hours for both engines. Total cost - less than $100.
 
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Ummm....is that bucket really held in place with duct tape?......

hamptonbucket.jpg
 
That bucket has been held there with duct tape for 3 years.
 
Great POST! This is great because these all brass inpeller pumps are on the all newer model bravo's including the 2005 280 5.0l. one question and comment.....

On the cover plate and inner housing where the "sidewalls" of the inpeller make contact I see some very light concentric circles or scoring- same ason yours. Does everyone have these? Are they getting bigger/deeper over time?

I had the exact same look last season and the local shop told me to replace the whole housing. I didn't, feeling that the 1/2 mm of scoring was inconsequential and I've watched my water psi ~12 running on plane.
 
Thanks for the "look see". Doesn't look too scary, but on my boat the bottom hose is the inlet and the top hose supplies cooling water to the exchangers. Also, have no issues with exhaust stuff since my engines are facing forward!:grin:

Thanks again for the excellent photos and descriptions!! Haven't done mine yet, but might just tackle them before this season.:smt115
 
Great POST! This is great because these all brass inpeller pumps are on the all newer model bravo's including the 2005 280 5.0l. one question and comment.....

On the cover plate and inner housing where the "sidewalls" of the inpeller make contact I see some very light concentric circles or scoring- same ason yours. Does everyone have these? Are they getting bigger/deeper over time?

I had the exact same look last season and the local shop told me to replace the whole housing. I didn't, feeling that the 1/2 mm of scoring was inconsequential and I've watched my water psi ~12 running on plane.

I took a chance on mine 2 1/2 years ago. They haven't advanced. I seem to be slightly more careful in shallow water than the PO. I would bet the dealer would replace the pump. When you can do the work, you can afford to let it go a little further.
 
Thanks for the "look see". Doesn't look too scary, but on my boat the bottom hose is the inlet and the top hose supplies cooling water to the exchangers. Also, have no issues with exhaust stuff since my engines are facing forward!:grin:

Thanks again for the excellent photos and descriptions!! Haven't done mine yet, but might just tackle them before this season.:smt115

Regarding the order of the hoses, I bet they're the same in our boats. I could be wrong about which is which, but I think they cross over 2' forward (back in your boat). Either way, it doesn't affect the process, as long as you keep them straight.
 
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John,

What did you use when re-installing your bolts and hoses? Permatex Anti-seize Compund comes to mind on the bolts, but what works on the hoses??
 
John,

What did you use when re-installing your bolts and hoses? Permatex Anti-seize Compund comes to mind on the bolts, but what works on the hoses??

I used whatever was lying around. I'll let experts recommend the right stuff.
 
With such a frequently replaced disposable vital part you would think the manufacturers would figure out a way to make replacement so much less complicated. Why not just open a door, replace the impeller and close the door?
 
With such a frequently replaced disposable vital part you would think the manufacturers would figure out a way to make replacement so much less complicated. Why not just open a door, replace the impeller and close the door?

Like on the genny?
 
Hi, Good job.

You are right about the deep grooves you have, We as a dealer Should or Would need to recommend that you replace the hole impeller housing, And it would not be to try to make extra money off anyone, It's more for keeping the boat running it's best and to try to prevent the possibility of any air bubbles from getting into the cooling system and at worst case letting the engine run hot, Or what normaly happens is the grooves will create air bubbles, And the air bubbles will give the water pressure sensor a fales reading and that will send the engine into guardian mode and sound a warning horn that you sometimes can not pick up in the scan tool history area, And to find it you need to be running the engine on the water while hooked up to a scan tool to find it in most cases. And of course that would give a dealer a bad name if any of the above happened.:smt089:grin:
But I can't blame you for wanting to get the most life out of the impeller housing as you can, Because of the cost of a newer style brass impeller housing kit is anywhere from $450.00ish up to $650.00ish dollars depending on the model you have.:huh:

Also FYI, I believe you for got one very important step we do for extra precautions, We always will lube the impeller housing up before installing the rubber impeller with either grease or dish soap, ect. We do this so that during engine start up the rubber is not not getting hot and worn out while waiting for the water to get to the impeller.:wink::smt001
 
Very good, I will have to admit, I am going to have to go back and find a few of the bolts you mentioned. I know on your very first post I do not see the bolt closet to the center.

Must be the old cannot see the forrest for the trees cliche'

I do like the detail though

+ something, and how about some more egg-nog and BJ, of course I never obtained an answer about what the "BJ" was, The only BJ reference I am familiar with just brings one things to mind.

I am gong to make a copy of your post and put it into a Word document, to go along with the other documents, so when I get either a net-book or just a note book to keep on the boat for my manuals and other documents for quick reference access.

Quick without looking in the manual, how do you set the Tri-data for night time illumination display?

Four pointy fingers :thumbsup:
 
John, when installing the impeller would some silicone grease or spray on the rubber vanes help to slip it in?
 
Great Post Appreciate the pics too! It would seem that the Mercury Designer / Engineer who had the responsibility on this design is not a boater. This is an old design and clearly in need of review. One side is accessible on ours but, the other is in need of a hired monkey. All I’m asking for is a practical solution.
I’m over 380 hours on our pumps and while doing my end of season impeller change I noticed we have the scoring mentioned. We picked up the new pumps and plan on putting them in when boat is wet again!
 

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