Changing raw water pump impeller on my 270 - Mercrusier Horizon 350 Mag, Bravo III

JonnyM

I was out the other day and was letting someone else drive my boat and we ended up in some shallow water.  Long story short, I was up on plane the next day and the temp alarm went off.  I am pretty sure it is the impeller.  I think I sucked up some nasty stuff and ruined it.  It seems like typical impeller symptoms... When I am putting around it is fine but when I get up on plane and the impeller is forced to suck water it overheated.  I am going to change it myself (this is my first), any tips along the way?

Dream_Inn

Use a large tie wrap on the new impeller when installing.  Make sure you take a picture of the old one so you know the correct way the blades get bent when installing new.  Pretty simple job.  Do not overtighten the bolts (I believe it is 7in/lbs.  Also, I pull the entire pump off to work on, makes it easier.  Before reinstalling, spray wd-40 or silicon type spray in both hoses.  It will make life much easier to reinstall hoses.

JonnyM

Thanks for the tips Dream!

davidbrooks

You are going to want to remove the alternator and move the fuel pump out of the way to get to it.  Just pay attention to the routing of the belt around the pulleys.  As mentioned the hoses will be tough to get off.  Make sure you mark them so you put them back on in the right order.... i can't remember if they were different sizes or not.  As dream said a zip tie around the impeller will help to get it into shape.  Look at the direction the rubber tines are bent on the old one first so you put the new one in the same direction.  It should reset it self but always better to have in in right the first time.  The last thing i would say it to not buy your parts off of ebay or some discount site.  If you find a place listing them much cheaper than others there is a reason.  There was a batch a while ago that wasn't quite to spec and wouldn't prime.  I know this first hand as i experienced it with my last boat and had to redo the job.  I don't use that mechanic anymore.  As a result i started doing as much as possible myself.

reneechris14

It is easier to get the hose clamps off the back of the pump if you pull it out a couple inches. I would also take the Caps off both ends of the heat exchanger and flush out with a hose it's also a good idea just to inspect it

Dream_Inn

davidbrooks said:

As mentioned the hoses will be tough to get off.  Make sure you mark them so you put them back on in the right order.... i can't remember if they were different sizes or not. 

Hoses are different sizes.

I agree with Renee.  Unbolt the pump entirely and pull it out a bit, then loosen hose clamps (much easier to get to that way).

Liberty44140

I just did mine this past winter. I left the hoses connected. Removed belt, alternator bracket and idler pulley and then loosened fuel pump. Water pump slid toward me and I opened the pump and changed the impeller with hoses on. Need a short, stubby 10mm wrench to do this. 

Liberty44140

I used these instructions to do it. Unfortunately the pics are no longer active. There are videos out there too. 

http://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=7491&p=72754

JonnyM

Thanks guys all good tips.  I will try to get some pictures tonight.

craigswardmtb

I second liberty's method. It wasn't bad with hoses attached. Those things are a bugger to get off. I'll be doing this on Friday. Except with a new Hardin SS pump with pulley. I sprung a leak at the pulley shaft. The lip seal failed.  So it was spraying all over the pulleys as I ran before I realized the issue. Rather than rebuild i went for an SS pump.
Good luck. 

JonnyM

Well, I pulled the pump out and the old impeller looked good.  I obviously changed it anyway.  I will put it all back together tonight.  It only overheated once while I was on plane.  It may be possible that I sucked a bag against the intakes on the outdrive.  I'm going to put it back in and run it to see what it does.

I read that scoring on the back plate can cause the impeller to lose suction but mine doesn't look too bad.

Old Impeller

OLD IMPELLER

Dream_Inn

yeah, your old impeller looks pretty good and the scoring doesn't look bad at all.  It definitely could be the bag thing, I've seen that happen more than once.

JonnyM

I was telling a buddy about the bag thing last night and he never heard of it.  Its happened to me at least twice.  My dad even had a bucket get logged around his prop and the boat wasn't moving at all.

Dream_Inn

Speaking of logs, I just heard a story at Rinkervous about someone having a hard time getting on plane. They slowed down and then put the boat in reverse...out came a huge log that had gotten lodged behind both outdrives.  I could only imagine the drag.

JonnyM

Dream_Inn said:

Speaking of logs, I just heard a story at Rinkervous about someone having a hard time getting on plane. They slowed down and then put the boat in reverse...out came a huge log that had gotten lodged behind both outdrives.  I could only imagine the drag.

Wow, that's crazy.  That's actually where my boat came from.  I have MDBoater's old 270.

Cableguy Greg

You have the plastic rear section of the pump. The wear plate can be replaced. Since your impeller is out, you might as well replace it. Dish soap will help you get it back in. I used the dish soap and the large wire tie to get mine back in. I sucked up a bag on my old 232cc. I heard the alarm go off, but it was too late. I ended up with a blown engine.

JonnyM

Cableguy Greg said:

You have the plastic rear section of the pump. The wear plate can be replaced. Since your impeller is out, you might as well replace it. Dish soap will help you get it back in. I used the dish soap and the large wire tie to get mine back in. I sucked up a bag on my old 232cc. I heard the alarm go off, but it was too late. I ended up with a blown engine.

Ouch!

I already have it back together and will test it out soon. 

rasbury

http://rinkerboats.vanillaforums.com/discussion/2972/recap-my-cooling-issue/p2 is a threw I had on this subject. And reading this, I miss tiki on the forum and hope he is well. It takes very little scoring for the impeller not to function. I'm not convinced spending 700 on the hardin pump gets you any further than the merc brass one- they are pretty however. I bought a kit for 100 bucks that has two ss wear plates and a shorter impeller that seems to work fine, have mentioned it on the forum but does not seem to catch on...i think the info is in that thread. It's a bigger the first time, alternator off, 3 10mm bolts to loosen the pump AND the mounting bracket, then the hoses. I can't imagine doing it in the bilge but then I have a generator to work around...good luck!

JonnyM

Thanks Ras, I already put it back together, we will see how she runs tonight (weather permitting).  I was able to get it out without taking the alternator out.  I am bruised and cut a little bit but I expected that.

Dream_Inn

@rasbury - my hardin pump was nowhere near $700.  I believe it was under $400.

craigswardmtb

I just paid 495 with the pulley and impeller included.  I would have had to rebuild the old one which likely would have been $140 in parts, then another $40 for the impeller, and $25 for the SS plates.  So for me it made sense to just go Hardin.  I'll probably rebuild the old one and keep it as a spare or sell it.

reneechris14

@craigswardmtb if it sprayed the idler above the pump, spray the barring real good with some oil on reassembly. 

rasbury

My kit with impeller was 100

LaRea

@JonnyM - where does your pump get water?  Is it from the outdrive only, or from the outdrive plus a thru-hull fitting?  (Single pickup or dual pickup)

If it's single pickup, you might have a partial blockage of the hose inside the outdrive.  The fitting at the transom can get corroded, reducing the water flow.  That would make it more likely to get stopped up by debris.  

craigswardmtb

A couple nice to haves as you do this. If in water have a wooden hose plug on the ready. This was the first time I did this in water so I had to deviate from my standard method and i detached the red inlet hose and plugged it while I worked. 10mm ratchet wrench is your friend on all the pump bolts. You cannot get a regular ratchet on the bracket bolts. At least a 6 pack to calm you down while you cuss at those 3 bracket bolts that are such a PIA to align and thread in on reassembly. 

JonnyM

LaRea said:

@JonnyM - where does your pump get water?  Is it from the outdrive only, or from the outdrive plus a thru-hull fitting?  (Single pickup or dual pickup)

If it's single pickup, you might have a partial blockage of the hose inside the outdrive.  The fitting at the transom can get corroded, reducing the water flow.  That would make it more likely to get stopped up by debris.  

It is a single pickup through the drive.

I actually just had that fitting replaced a week ago but it could still be clogged.  We had some flooding in Pittsburgh this weekend so my boat is still on the shore and haven't been able to test it out.

JonnyM

I put the boat back into the muddy Ohio River last night and ran it for 30 minutes.  It didn't heat up and ran fine.  I didn't get it up on plane because there is still too much debris in the river right now.  So far so good.