How to Change Impellers in 8.1's with Pictures

[Hampton]

John, when installing the impeller would some silicone grease or spray on the rubber vanes help to slip it in?

It's just not that hard.

 

[Hampton]

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!

How much did you pay? My scoring hasn't changed in 3 years, so I feel fairly confident that it won't be an issue over the next few years. I do think I'll carry a spare pump on our trip though.

 

[Hampton]

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.

Good observation. It's not in the pic, but it doesn't hide. It's just a bit above the view of the pic.

 

[Hampton]

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

I'm going to pure up my post. I left out 3 key points:

1. Lube the impeller - I used the foamy type of dish soap.
2. OPEN THE THROUGH HULLS!
3. 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.

 

[osd9]

You also left out the pre and post medication recommendation......I'd say 2 advil before and then 2 more immediately following.....larger sized men may need more....

 

[Skuza]

Nice write-up. Your style pump is different than a 7.4. I like the drain hole on the pump for winterizing. Ours doesn't have this and it always concerned me that water is trapped in the housing.
On a side note the duct tape is funny and totally ghetto! But isn't that why we love the stuff? Because it actually works on stuff it shouldn't!

 

[my3sons]

Great post John, thanks for taking the time. the pics are great.
I haven't had my pumps apart yet but will be doing it in the spring. You were wondering about cost of a complete pump, I have always carried a spare so when we bought the boat last year I picked one up through ishopmarine. I paid about $325 if I remember right. Don't know if it's overkill, but I take the impeller out of the spare so it doesn't take a "set" while it's laying around in the bilge box waiting to hopefully never need to be used. fwiw I have always used petroleum jelly to lube the impellers, don't know if it's right or wrong but in many years of boating, I have never had any problems. Thanks again

 

[Chris R]

Nice job John. I'm saving this as a favorite in my boating folder.

 

[dpmulvey]

Excellent post. How often do you change the impellers? Saint Max has 2007 6.2's with about 70 hours on them.

 

[douglee25]

You're going to find a wide array of answers on this one. They 'say' you can go maybe 1-3 seasons depending on usage. Personally I would change them out yearly as cheap insurance. The impellers tend to set over the winter months while the boat sits. When the blade sets, their pumping efficiency dramatically decreases.

Doug

 

[skolbe]

Dang John.....Your 8.1's are different from mine. I got stopped dead, because I didn't have long enough of an extension (no wise cracks) for my socket wrench with me. My engines have a traditional tensioner, which was great for getting the belt off, but that was my stopping point as I couldn't get to the bolts to remove the pullys. Hindsight being 20/20, I probably could have removed the pully wheel to get enough clearance, but didn't think about that until my brain thawed out.

I'll have to try again Weds. It was pretty &%$^%$ cold in the bilge today with temperatures at 18 degrees inside the building, and three feet of snow outside. My little shop light did keep it warm enought to prevent the snot from becoming snot-cicles though.

So take some pics of your setup.

 

[Scottster]

Great post. My 340 is a year older than yours but identical to the pictures you took. I will try to change mine at the end of next season. I appreciate you taking the time to take pictures and write this up. It will certainly make my first try easier.

Thanks again.

 

[Fun Times]

I'm going to be doing mine soon, but the boat will not run until April. What type of grease can I use to lubricate the impeller? Is there any thing specific or will any grease do? I don't want to run the risk of the grease reacting with the impeller, or dish soap evaporating before I have a chance to run it.

Well the mercruiser service manaul will say do not let them sit for longer then a few hours, So that is a tough call kind of, But then again mercruiser sells a impeller housing kit with the impeller installed already and you know it has been sitting around on a shelf for sometime. Volvo sends a silcone type lube with their impeller that works good. We have used with pretty good success the blue wheel bearing grease that you would use on your trailers wheel bearings for installing the impeller, Or you could use either mercruisers special lube 101, Or 2-4-c with teflon could work. Here is a link to them, Look at numbers 8 & 9. http://www.mercruiserparts.com/Show...se.png&inbr=100000&bnbr=1&bdesc=GREASE+&+LUBE We have used all of the above before. Or you could use the KY if you have any extra.:smt043J/K:smt001 So it's up to you, But really you should be ok with anyway you go here. Good luck with it, Stay warm.:smt001

 

[Hampton]

Excellent post. How often do you change the impellers? Saint Max has 2007 6.2's with about 70 hours on them.

My professional (amateur) recommendation is between 2 and 3 years. If you leave them cooking in salt all of the time, and/or let them sit unused for long periods, or put tons of hours on them, I would shoot for 2 years. If you use them at regular intervals, moderate hours, and run in fresh water or rinse your engines, then I would feel comfortable at 3 years. I felt mine looked much, much, much better after these 2 1/2 years than they did from the first 3 years - I've been fresh water rinsing them for 2 years.

I've been putting 50 - 75 hours per year on the boat (50 the last 2 years, but I run it very frequently, just not very far except for about 4-6 moderate (50 - 70 miles) trips per year.

 

[Hampton]

Dang John.....Your 8.1's are different from mine. I got stopped dead, because I didn't have long enough of an extension (no wise cracks) for my socket wrench with me. My engines have a traditional tensioner, which was great for getting the belt off, but that was my stopping point as I couldn't get to the bolts to remove the pullys. Hindsight being 20/20, I probably could have removed the pully wheel to get enough clearance, but didn't think about that until my brain thawed out.

I'll have to try again Weds. It was pretty &%$^%$ cold in the bilge today with temperatures at 18 degrees inside the building, and three feet of snow outside. My little shop light did keep it warm enought to prevent the snot from becoming snot-cicles though.

Scott! Sorry, man. Get back in there, slide that pulley over, and get to the meat of it, STS.

 

[northern]

How did you get the exhaust hoses loose on your muffler? When I changed my risers last fall it was a bear of a job. I used screw drivers to loosen the hose to the metal riser, if I did that to loosen the hoses to the muffler I would have brocken the fiberglass.

 

[Bodkin Creek George]

John,
We are up here in Maryland where the boating season is shorter than yours. How often do you change the impellers down there?
George

 

[osd9]

John will answer to the specifics of the 340DA's exhaust.

I'll comment 'generally' as I also have remove exhaust components on my 410DA for an impeller change.

BEFORE removing the exhaust, mark all the components circumfrences with a marker...I used a red magic marker. That will come in very handy during the reassembly because it will let you know when you have the parts all back together the same way that they came apart....specifically, it will let you know if you're done or if you have to continue to heeve-ho to get them in further.

For disassembly, first try to just take them apart after loosening the clamps. If that doesn't work, then spray with a Silicone aerosol. For re-assembly, I found it MUCH easier to pre lubricate with the silicone spray all the parts that are to be re-joined ....do NOT use WD-40 as it can harm the composite exhaust components. You may also want to consider new clamps as the threads have a tendancy to gall up.

 

[Hampton]

John,
We are up here in Maryland where the boating season is shorter than yours. How often do you change the impellers down there?
George

It's been 2 1/2 years - they looked good, but I think they were about ready. Probably could have gone another year, but not without risk. We have a big cruise coming up in June. About 125 hours.

 

[Hampton]

How did you get the exhaust hoses loose on your muffler? When I changed my risers last fall it was a bear of a job. I used screw drivers to loosen the hose to the metal riser, if I did that to loosen the hoses to the muffler I would have brocken the fiberglass.

I didn't loosen the hose from the risers. When I disconnected the hoses from the fiberglass, I just shifted the muffler a little and rotated it a little without much force and the fiberglass let loose without much difficulty at all. I was not hampered or slowed or concerned with this process. It worked fine.