Replacing Impeller on seawater pump - 8.1s Mercruiser

[rondds]

I figure having done this 3x on my previous boat (7.4L MIE), how hard could this be, esp on the stbd engine, which is purported to be the "easy" side. As it turns out this is a 2 (two) advil job. Took me about 3 hours and half that time was trying to figure out how to tackle it.

I read the manual and got the serpentine belt off no problem. This is what I'm looking at now.

Took this pic so I'd remember which hose goes where. This pump is not marked IN and OUT or LH. I also made a note that the green hose is on top.
...

Like my previous boat, the sequence of things is to get the pump to drop into the bilge, get the hoses off and pull it out of the bilge and replace the impeller on the dock. Back this bolt out of the top of the bracket, get two more off the back of the pump and it comes off the bracket.

But wait, there's these two "wires." A sender? Not sure. Put the top bolt back in (not enough slack in these hoses to let it drop down), stop everything and start nosing around.

Turns out these are the air hoses that allow you to blow seawater out of the system with the little bicycle pump Merc clips to the motor. How the heck to you get themoff the pump (?) Phone call to Rick (mistercomputerman). He says you have to that little collar in and pull the hose out. Pretty simple.

Now the pump can drop to the bilge floor, after which I was able to wrestle off the hoses. I was surprised to see that this entire pump is bronze. No crappy plastic housing that I'd become accustomed to. Also found it interesting that it was sprayed while on the motor (apparently). Time for some forensic mechanics...

Could it be that this pump was never off the motor (see the untouched paint on the top bracket)? These motors went in prior to the 2008 season and have 180 hours on them. The paint flaked off as soon as I put a socket on that bolt.

4 short bolts (size 10 mm wrench) and you open up that seam to reveal the impeller. I marked the holes where the bolts came from with wite-out. Otherwise you may put a bolt in a spot that is a mounting hole, not a sealing hole. The impeller had taken a set but was otherwise perfect. No cracks starting where the vanes meet the hub either...

This is the other half of the pump. My buddy CJ told me he's on his 3rd or 4th pump b/c of scoring. Is this bad? I don't know? But it's going back together as-is (other than with a new impeller and new o-ring) b/c it was working fine before and the impeller was not ragged. The rubber o-ring fits in that little track around the perimeter of the water passage (see above picture).

Part number I guess (?). You can see some of my wite-out on the right-most edge of the flange...

Extract the old impeller, squeeze the new one in with copious liquid soap, drop in the new o-ring and put the two halves back together. Then more fun and games as I wrestle it back into place, getting hoses on first (more liquid soap), then the mounting bolts. Last step is the little air hoses and it's time to test. Oh, remember to open the seacock back up. Sudsy water from the exhaust = success.

I think when I do the other side, I will release the output hose not from the pump nozzle but from where it connects to a T further downstream. The T sends water to the Cool Fuel unit and then onward to the oil cooler (tranny or crankcase, not sure what's the first stop).

Also invested in a set of these to get to the two 10mm bolts at the back end of the pump next time. It took probably 45min to back out and re-tighten these bolts b/c there's just no room to swing a conventional box wrench more than maybe a sixth of a turn. And you can't see the bolt head. Quite a bit of "Use the Force Luke" going on during this process. Force wasn't the only F word I was thinking of.

The red arrow is where the 10mm bolt head is located. The Yellow arrow is where the other bolt head is, but on OTHER side of the pump (the side closer to the center of the motor)

As with EVERYTHING else in a boat, the problem here is access. Not a fun job and I can see how the mechanics of the world earn their $$ on this job. Not the type of job to do when it's 87 degrees out.

My port pump is leaking from the front lip seal/bearing. I am going to replace that pump with a stainless steel aftermarket one. It is actually just 1/2 a pump - the impeller housing half. The nozzle end with the air hose fittings stays. The improved design of the aftermarket pump includes a backing plate that protects the nozzle side from wear (see my pic above). It uses a different impeller, but it is still a standard Merc impeller (not sure of the part number). More pix to follow as that chapter unfolds - that is, IF I can get to the darn thing on the other side. Rx there is Take three advil 1 hr before job, then 2 advil six hours after initial dose.

Here's the impeller I took out...

 

[Lazy Daze]

Ron, I have yet to do this on an 8.1, but can you get to the bolts that hold the bracket on? Look for easier bolts to get to that would loosen the whole she-bang?

 

[rondds]

Dennis. That could very well be. I don't know. Maybe someone else will chime in and tell me how much futile labor I went through. Possibly taking off the tensioner pulley but not sure.

 

[mwph]

Nice write up. The pics are great & clear informative comments too. The set up looks very similar to my 7.4L.
Good question Dennis, I can't remember for sure but I may have done just that on mine.

side note- love those wrenches!

 

[rondds]

I was turned on to those wrenches by a friend, J Levine here on CSR. I schlepped over 2 docks in the pouring rain to his boat to break in and steal his set, but he's anti-metric. So it was a small 10mm box wrench for me. Painstaking process.

 

[Fred]

Ron,
No reason to remove the hoses if you can get to the screws to pull the front of the pump.
On my 320 I replaced the impellers 3 or 4 times without ever removing the water hoses or the quick drain lines.
Fred

 

[Lazy Daze]

Well that's weird. When I first looked at this thread, only the first pic (and the writing to the point) showed up. I thought it was a "I'm stuck" thread - didn't realize it was a how-to. Very nicely done! I've contemplated the Jabsco (bronze) pumps as a replacement as I know they've been around for a long time and are servicable. I haven't come across that SS pump before. Good fine - it'll be interesting to see how those work.

I have a skiing buddy who refers to ibuprofen as "Vitamin I"!

 

[Danny Troy]

I just did this PITA job two weeks ago. I posted a similar question, asking for help, and was directed to this thread, which was an immense help. Note that on my 8.1 the air pressurizing hoses did not connect to the water pump, so I didn't have to deal with that issue. Here's the thread, complete with photos:
http://clubsearay.com/showthread.ph...pellers-in-8-1-s-with-Pictures?highlight=pump

I agree that leaving the hoses connected to the pump, and disconnecting them where they connect to the heat exchanger (or whatever it's called) would make the job a lot easier. I actually half did that, in that I was able to disconnect the black hose at that point, but the red wouldn't budge. When I do this job again, I will first deal with freeing the red hose at the heat exchanger, and leave both hoses connected to the pump.

Either that, or switch over to a crank mounted water pump, which is what Mercruiser should have done in the first place:
http://www.michiganmotorz.com/crank-mount-water-pump-wbracket-p-300.html

 

[rondds]

No reason to remove the hoses if you can get to the screws to pull the front of the pump.

Fred, you got me thinking. If I drop the pump down off the bracket, I should be able to get to the 10mm bolts. The box-ratchet wrench should make getting the bolts off tolerable. Then the nozzle end of the pump is just suspended from the hoses while the impeller is replaced. I'll certainly give it a shot on the port motor. Problem then becomes getting the 2 halves of the pump back together in an extremely cramped area, while not messing up the placement of the o-ring. I guess if it can be done in a 320 it can be done in a 380 (?)

When I first looked at this thread, only the first pic (and the writing to the point) showed up.

Dennis, I accidently hit POST way before I was done and it took a while to get the rest of the thing composed. Sorry about that.

 

[MasterFab]

Ron,

I normally pull the nuts off the tensioner bracket, and remove the bracket and the two pulleys as a unit - just lay it aside. Then, you can simply slide the entire pump, and bracket, off the mounting studs (after the air and water hoses are removed, ofc). Now, you can remove the pump from the bracket much more easily, change the impeller, and then reassemble the pump to the bracket. Back in the boat, it slides right back together much more easily this way. I like the way you did it though - more like pulling teeth!

Dale

 

[Fred]

Ron,

Use a heavy greese or vaseline on the O ring to hold it in place. I used a pure silicone greese.

Fred

 

[Lazy Daze]

I believe that o-ring is standard rubber, which means it's best to shy away from petroleum-based greases. But the silicone grease (you can buy it as "plumber's grease" at a home store) is perfectly fine. And definitely be careful with that o-ring, it's not uncommon for it to get out-of-place during reinstall. I've seen some other guys use a special o-ring adhesive (Loctite brand, maybe?) but I've never used it, myself.

If you put a zip tie around the vanes of the impeller, it can help to get it started (dishwashing soap was a good idea, to) - then clip the tie and finish it off.

 

[Lazy Daze]

Dennis, I accidently hit POST way before I was done and it took a while to get the rest of the thing composed. Sorry about that.

No worries - at least I know my computer wasn't (?isn't?) possessed!

 

[Danny Troy]

Ron,

Use a heavy greese or vaseline on the O ring to hold it in place. I used a pure silicone greese.

Fred

I carefully installed the O-ring, so it wasn't twisted at all. Any twist will cause it to pop out. I was able to put the pump together without any sort of grease (which should be safe for rubber) or adhesive. Just take your time and watch it from the side as you put the halves together. This, of course is a lot easier if your at home on a workbench, and not sitting on the floor of the boat.

 

[Donetalkin]

Any chance you can get your pictures fixed? This is a great write up, i'm about to attempt this but would love to see the pictures.

Thanks

 

[rondds]

Looks like some got fixed on their own. Others I could re-post but I can't figure out how to EDIT a post

20 minutes later:
FIGURED OUT HOW TO EDIT. GOT THE MISSING PIX BACK UP USING SHUTTERFLY. HOPE THIS HELPS!!

 

[Mittens]

I remove the braket and 2 pulleys, and then the 2 main hoses, and slide the whole thing off. it does suck to do the port motor. starboard was WAY easier.

 

[R-and-R]

After burning thru an exhaust hose, I’m about to embark on this project. Hopefully I’ll be able to post some success pics later this week.

Ron, did you have any success with the Stainless replacement?

 

[rondds]

Yep. 4th season on one motor, 5th on the other.

 

[mrsrobinson]

Old thread I know, but I was thinking of doing this one myself versus the mechanic. I am surprised to see the bolts/nuts are metric. I have those wrenches for when I work on my German/Japanese cars, just surprised to see Merc is metric.