60 Johnson RDS-22 40Hp Impeller Issue

[dcygan]

Hi all, I've got a problem with a new impeller and the fins reversing orientation after being installed and then starting the engine. I have taken the lower unit off four time and each time, the same issue occurs. Attached are two photos, one showing the problem with the reversed fin direction, and the other showing after I've fixed the fins.

I've take the cover off of the thermostat housing and removed all of the components so there's no obstruction allowing me to make sure water is circulating. Water pumps out for the first couple of seconds then stops. I then remove the lower unit and fix the impeller fins and again, the same issue, no water and some of the fins again change direction.

I have tried turning the shaft by hand and the problem doesn't occur so I'm at a loss as to what could be causing this. I'm wondering if the water pump housing is the problem.

I'm testing the engine in a barrel and the water level is about 4 inches above where the water pump is. I have also made sure that water can freely circulate through the engine and copper feed tubes.

Just so you're aware, compression in each cylinder is 120 PSI.

Any suggestions will be greatly appreciated.

Thanks,
Doug

 

[F_R]

There ya go, just proves five things.

1. We worry too much.

2. Even if you installed all of them backwards, they would flip over correctly as soon as you start it.

3. When you turn the motor off, it bounces backwards off the final compression stroke, which is liable to flip a vane or two. See #2.

4. We all know this, but nobody wants to say anything for fear of starting a fight.

5. This does not apply to ALL impellers. Some do not flip so easily.

 

[dcygan]

Okay, that makes sense, but I'm still not getting any water circulating in the engine and it's overheating with or without the thermostat in place. Any thoughts?

 

[F_R]

The cooling system in those motors is rather sophisticated, but also very reliable. So it is hard to guess what is wrong when it doesn't work. The water pump is the prime suspect, along with not getting enough water to the pump. Air leaks into the pump would be high on the list also. Put the thermostat parts back in, they are part of the system, and it should pump water even if the 'stat is closed. The check valve below the thermostat must be in place or it will suck air and not pump!!!

I hesitate to list rare possibilities for fear of sending you on a wild goose chase. But here is one just for example: There is a core ("freeze") plug on the rear of the exhaust housing. There are four or five small holes behind that plug, which have been known to get plugged up with trash. Like I said, rare.

More likely is air getting into the system from somewhere.

 

[dcygan]

F_R, thank you for being so helpful, I very much appreciate it. I agree, it sounds like an air leak. I think what I'll try tomorrow is to run the pump using an electric drill connected to the shaft and see what happens. All of the times that I ran the engine I had the water in the barrel about 4 inches above the top of the water pump to ensure that it was fully submerged. If there are air leaks then they're somewhere above the pump. Do you know if there's a cooling system diagram for this engine?

 

[F_R]

I've never seen a diagram. For whatever it's worth, I can tell you how it works. Water from the pump goes up one tube to the powerhead, circulates through the powerhead, and then presents itself to the thermostat. If the 'stat says it is too cool, the water goes through the relief valve and back to the pump through the second tube. Then it recirculates. This continues till the 'stat says it is warm enough, then it is discharged and replaced with fresh lake water. This process continues constantly, with the 'stat opening and closing as necessary to maintain proper temp.

A couple places air can get in are:

1. Under the water pump, if not sealed to the gearcase.
1.5 Through the drive shaft hole in the pump housing.
2. A cracked gearcase beween the pick-up screen and pump.
3. Leaking water tubes or grommets or water pump inlet cap.
4. A hole in the exhaust baffle plate on the side of the powerhead
5. A blown head gasket
6. Other damaged or home-made gaskets
7. Some other gotcha.

EDIT: Dare I suggest you run it on a boat on the lake to see if you really have a problem?

EDIT EDIT: Running it with a drill is next to useless. There is no exhaust / air trying to get in.

 

[dcygan]

F_R, when you mention air leaks, does this also refer to water leaks? What I mean is that if the pump is fully submerged then there's no air, just water. And, is sealer supposed to be used when installing the Stainless Steel Impeller Housing Plate and the Water Pump Housing? I haven't seen any reference to it being used, but perhaps I'm missing something. I did notice that there is some minor pitting in the pump housing where the impeller goes so I just bought a new housing to be on the safe side, if this is the problem.

 

[F_R]

Sealer should be used under the SS plate where it sits on the gearcase. Also, that area should be clean and no serious nicks or chunks missing. Remember, the pump is NOT externally surrounded by water when running. It is surrounded by exhaust which blows the water out of the area.

No sealer is required between the SS plate and impeller housing.

 

[F_R]

I have only seen two or three motors with this crack out of the thousands I've serviced. But there were enough that OMC changed the design in 1967.

 

[dcygan]

Thanks for clarifying the need for sealant below the SS plate because of the exhaust, which makes sense. I'll add add it to the bottom of the SS plate once the new pump housing arrives. The pitting inside the original housing could be considered minor blemishes and not pits, but I can feel them with my fingers so I'd rather not take the chance since I found a new one on eBay for $17. And, I have not taken the side cover off to check for the crack shown in the photo, but I will today and let you know. Thanks again!!!

 

[dcygan]

I pulled off the cover and screen yesterday and the housing is fine, no cracks. I'll assume that it's the SS base plate that needs sealant. I'm hoping that the new pump cover arrives by Friday so I can get it reassembled for the weekend.

 

[dcygan]

So the new water pump housing arrived along with new seals for the copper tubes. I replaced them even though the originals were still in great condition. I sealed the base plate and housing to prevent leaks. I installed the lower unit and aligned the copper tubes. Everything went together as it should and the impeller was installed with the fins turned the same clockwise orientation as the engine. Still no water is pumping. The engine got to 190 degrees and then I shut it down. I took the thermostat cover off and there was no water nor were the parts damp. I am at a total loss as to how to figure this out. It's simple plumbing, but yet it fails to pump. I'm desperate for ideas. The videos that I've seen on Youtube all show water coming out the exhaust hole on the back of the engine, but mine nothing comes out except for exhaust.

 

[dcygan]

And here is a photo showing the barrel of water with the water level above the pump and pretty much at where it should be with the boat / engine sitting in a lake.

 

[Willyclay]

When F_R posts in a thread, I pay attention because he teaches me so much! My RDSL-21 is long-gone but my experience with it caused me to look at the parts diagram for your model. Yours should have a "key" to engage the impeller on the driveshaft and I have not seen one in your pictures or a mention of it. Any chance it is damaged or missing? Also, I recommend you run the motor deeper in your barrel, if possible, to help insure the water pump is getting primed. Just keep the level slightly below the exhaust bypass outlet opening.

 

[dcygan]

Willyclay, Yes, I'm sorry, I should have mentioned that there is a woodruff key. I can take a photo, but the one below shows that the impeller is locked to the shaft and that it tuns, hence why some of the blades reversed direction. F_R mentioned that that is caused when the engine stops it rotates backwards briefly.

One of the things I did last night was to take the thermostat housing off again and I put my mouth to the opening and I was able to siphon water all the way up so that tells me that there aren't any cracks or gaps between the water level in the barrel and the thermostat housing. I will empty the barrel this morning so I can lift it higher or I'll let out the air in the tires to lower the trailer/oat/engine so it sits deeper in the barrel.

If that doesn't work, then I'll take it apart again and put the lower unit into the barrel so that the pump again is below the water and use a drill to see if it pumps anything at all. If it doesn't, then the problem is somewhere in the lower unit.

 

[racerone]

Perhaps too many bubbles are the troubles.-------Test this thing in the lake.

 

[dcygan]

I took it apart one more time and replaced the impeller with another new one and now the pump works. The previous new impeller was slightly shorter ~1/16" than the one I just replaced it with. All seems good.

 

[racerone]

Was the " short " impeller a factory new part or something else ?

 

[dcygan]

It was one that I bought off eBay from a seller in NY, but it shipped from China. It arrived in a ziplock type plastic bag with nothing else, no part number or any writing on the bag. Fortunately, I had ordered another as a spare from Amazon and it arrived yesterday.

 

[Willyclay]

Glad to hear you whipped it. Good luck with that great old motor!