OMC Impeller replacement

[floattest]

I'm changing the impeller in the 1979 OMC sterndrive. I'm doing it chief's way and so far so good. Maybe someone can add the link to chief's process. I'm not sure how to do that.

Now the swivel housing is stuck. Can't get it loose to get to the pump. I've tapped on it as hard as I like to and it's not coming out. The four stainless bolts we're "glued" in with some hardy sealer, they were a bear to get out. I'm thinking I'm fighting the same sealer now where the swivel housing holds the impeller housing in. I shot some liquid wrench up into the holes last night, I'll try again to get it loose. Another question I have, the seloc manual says to put permatex on both sides of the impeller when installing, what's that, what's it do?

I thought I'd take some pictures for all to see chief's method in use.

I can see why some experienced wrenches don't like this way. Awkward to work upside down. Other than that it seems a reasonable method. I was suprised to learn that the 4 small bolts on the top that go into the exhaust housing hold the whole lower on. Luckily I had some support under the skeg when she "dropped". The shift cable is being protected from strain with the lower and exhaust supported and swung out of the way. Dang newbies .

 

[floattest]

Re: OMC Impeller replacement

OK, I've found the answer to one of my questions. The permatex is a sealer. And I misread the seloc book part about this. It goes on the outer 1/4 inch of the impeller PLATE, to seal between the swivel bearing/impellerplate/impeller housing not on the Impeller itself.

The other question I still need help with. How to break it loose. Let me rephrase that. How to get it to release. I don't want to use the B word.

 

[floattest]

Re: OMC Impeller replacement

I got the pump out with repeating hammering. No heat. Nothing damaged.

Here are the pics of the impeller and I took a shot up into the upper. The impeller is intact. Maybe it was working OK. Lot's of corrosion in the upper housing water passages. I'll do my best to clean it up. I'm considering back flushing all the way from where the water goes into the heat exchanger. Is that legitimate?

The splines on the pump shaft look a little worn. I'd say 85% left from new. I'm going to put it back the way it is.

I realize I'm talking to myself, but hopefully somebody will benefit. Maybe it's also worth some boat karma.

 

[floattest]

Re: OMC Impeller replacement

I realized that all the corrosion in the picture looking up into the upper is the impeller housing. That's being replaced which is good. The old one doesn't want to come out, which is bad. Looks like the whole pump, housing/impeller/plate, should just drop out. It may take some more hammering. I'm not a big fan of banging on this old girl. I don't want to make things worse.

Here is a pic of the drive shaft. I think it's ok but it feels a little sloppy, some backlash, when in the upper housing. It feels good in the lower. Those splines are healthy. I remember a thread, more than one, about people spinning that shaft. Not good. I'm reconsidering putting it back in.

Any comments?

 

[bruceb58]

Re: OMC Impeller replacement

I hope you are going to replace that impeller. The vanes should be sticking out straight. They have a very bad set in them.

 

[floattest]

Re: OMC Impeller replacement

Yes Bruce, that was the plan.

I'm going to replace the drive shaft as well.

As I mentioned the impeller housing is being very stubborn. It seems to be stuck very badly to the bottom of the bearing housing.

 

[floattest]

Re: OMC Impeller replacement

So glad I'm doing this. As anyone can see from the pics this impeller and housing are a mess. Boats been in Puget Sound and maybe the guy before me didn't flush it very well.

Got everything ready to put back together.

I should clarify from the earlier posts that I was wrong on a few things.

It was the Swivel bearing that was the first part that I couldn't get out. Then once I got that out I had to "pull" on the impeller housing to extract it. Of course, the bearing housing above it came out as well. I put the hammer away. Got it with a puller. Learned that the three plugged holes in the housing are for pulling the thing out.

The Imeller housing and bearing housing were coroded together pretty good.

Got that apart now and things cleaned up.

Here's the question. The hole visible in the bearing housing flange appeared to be plugged with some sort of caulk or putty, white in appearance. It looks to me like that hole is for the pump function. I'm not sure if I should leave it cleared out like in these pics or seal it off. I'm afraid if I leave it open that water will get in my gear oil. Anybody know how this pump works?

Any comments are appreciated.

 

[floattest]

Re: OMC Impeller replacement

I got my answer. Talked to a tech at TC electronics. You can find them if you look. They have a guy that answers questions for a few hours a day.

He knew exactly what I was talking about. This extra hole in the bearing housing was added back when to increase water flow, but the side affect was increased exhaust gases that would burn up impellers.

Enter "any cheap ol sillycone", plug it up and put it back together.

So for my trouble I will have new water pump kit, new drive shaft, cool running SBC and lots more knowledge.

I will post more when this thing is pumping water.

 

[floattest]

Re: OMC Impeller replacement

Just a quick update. I have the thing put all back together. Not bad, that permatex 2 is some nasty stuff. I think I might take the drive off next time. If dealing with the shift cable can be managed, then I think it's worth it to have this thing in a better position to work on.

Unfortunately I haven't run it yet, so I can't report on how well I did. Won't be able to for a couple weeks. I won't let this thread end until I have good news to report.

Advice for OMC owners. This is not a simple task. When these guys tell you to get a genuine OMC manual, do it. The seloc manual is pretty good, but it leaves you scratching your head sometimes.

Here is a new question. In the picture where you can see the old impeller and its set in the vanes, does anyone know if this is the correct set. Or another way to ask the question, which way does the drive shaft rotate. I'm asking because the Seloc book, which is all I have, shows the pump shaft/plate/impeller being installed into the housing and the directions say "rotate the shaft clockwise until the impeller seats into the housing". Well, it depends on if you are looking down or up which way is clockwise. I installed it with the set as in the picture of the parts I took out. But that disagrees with the Seloc book it seems. I'm worried that maybe it was wrong when I took it out and that was part of my problem.

If an impeller is installed with the incorrect set direction will it be obvious on first run, meaning will it just not pump or will it pump half power or something.

I do have a genuine manual on the way (what took so long!).

I have a feeling I'll be pulling it apart again. Oh well, it'll be easier next time.

Sorry I can't report how it works after this installation, like I said, I'll wrap up this story when I can.

 

[Howard Sterndrive]

Re: OMC Impeller replacement

Thanks for posting that! The next time you do it , it will be simple....

I've never seen the point of working upside down like that.... once you learn how to undo the cable, and wait for penetrating oils to do their thing.... the drive can be off in about 20 minutes.

 

[Lyndy]

Re: OMC Impeller replacement

Just some clarification please. You mentioned "Swivel Housing" more than once but the pictures you posted do not show it. The Swivel Housing mounts to the top of the lower gear case with bolts and the the splined shaft coming out of the bottom of the upper gear case slides into the Swivel Housing. When you mentioned the Swivel Housing were you talking about the drive shaft stuck in the Swivel Housing? When I took mine apart the easiest part being removed is when I slid the Upper Gear Case away from the Lower Gear Case. Now, getting the impeller and its casing out was a different story.

 

[floattest]

Re: OMC Impeller replacement

Lyndy,

Yes you are correct. My nomenclature was not correct. I think I was refering to the swivel bearing. The part that holds the impeller housing/impeller/impeller plate in. It has the four 5/8 bolts going up into the upper.

I got it all back together. It pumps water. I'm not convinced it pumps more than before, but at least I know what I have. I wonder how well it's sealed.

I'm going to test the amount it is flowing and I'm working on the manifolds now. Not sure why it still gets hot.

I'm sure by the time I'm done I will have gotten intimate with every part of the cooling system.

I wish I was boating, but that's not the boat's fault, it's mine.

 

[Howard Sterndrive]

Re: OMC Impeller replacement

In order for heat to get out of the engine, cooling water has to get out...... through the manifolds and risers.
If the impeller is pumping and you're still overheating, maybe the water can't get out.......risers and manifolds are suspect.

 

[THE BEEF]

Re: OMC Impeller replacement

Pump about 12 shots of OMC triple guard grease in the swivel bearing and see if your overheat problems stop.
Beef
PM me ,I think I can Help.

 

[floattest]

Re: OMC Impeller replacement

You are all on the right track.

Look at these pitiful pictures.

I should be ashamed. My boat was keeping me on the beach with good reason.

Well, soon it will have all new mani's/riser and then we'll see if I'll be able to go get some dungeness out in the sound.

wish me luck.

 

[Gary H NC]

Re: OMC Impeller replacement

Yikes! I think you found the water flow problem!

 

[floattest]

Re: OMC Impeller replacement

Beef, yes I did that, greased the heck out of the swivel bearing.

Here's the good news.

With the new manifolds I got her out and was able to test her at various speeds and sustained high RPM runnning on puget sound.

It has center riser manifolds from BARR. It's the universal kit and it installed easy and seems to work great.

Felt a little but bad about dunking right into the salt, but hey it's where I live and that water is begging to get cut up.

Temp was a constant 175-185 by the dashboard gage. I wonder how accurate it is.

After it got up to temp in about 3 minutes it stayed steady.

Ran at 3800 for about 10 minutes, nice!, around 32 mph at that RPM I think. forgot to look at the GPS, was watching temp.

I'm ecstatic to have her back together and running, I can save the last half of summer.

The bad news is that the upper is sucking a little water somewhere and getting milky oil. The lower is good. Intermediate get's a little coloration, but not like the upper. New seals are in order I think, but I'm not pulling it apart until I store it up.

She also stalled a couple of times at low Rs. My fault, I haven't completely tuned her yet.

I'll change the oil in the upper a few times and use her.

What a sweet ride she is. Feels good to be able to now look at working on cosmetices and accesories instead of the engine bay.

On my other post about the manifolds I'll post pictures of the install. Othe OMC owners may try this if they need new manifolds. I replaced every piece from the heads to the intermediate plus hoses and fittings for 925. Looks good too. I'm thinking I'll paint them blue over the winter to macth engine. maybe.