TOPIC: Still having troubles with water pump

Do you have a manual for the motor? If, so did you make sure the impeller isn't in upside down and the vanes are bent the wrong way. I work mostly on Scotts and their impellers have a mark on them that faces up when installed and I always ck the manual to make sure.
I have a Merc factory manual out in the shop and I'll take a look at it when i get out there. In the meantime a Merc guru might chime in to help you.
It sounds like you have done the the right things to check it out.

Thanks Mr. Fish. I guess it is about time I go and get a complete manual. 30 years ago when I first started doing some basic work on it and when I didn't have any $ to speak of, I went to the Toronto Reference library (remembering this was before the days of Internet) and took photo copies of the sections I needed. Those photo copies have been with me ever since! Although I have sections showing the tear-down and rebuild of the LU, it doesn't show the direction of the vanes. Dave confirmed the direction for me....but now that I think of it, I've had the impeller out a few times since then and maybe I put it back in incorrectly. I'll have to check that.

First time I changed the impeller on my older Merc, I used a Sierra kit that was made to fit several models. There were several gaskets that looked the same but weren't. The gaskets that go above and below the stainless plate are different. The one I used under the pump housing was the wrong one. No circulation at all. I carefully examined all the gaskets and compared them to the plate, and found the error. Works fine now. Don't know if your kit had multiple gaskets, it's a different model than my old 650.
In the photo, the stainless plate is at upper left.

Thanks for your input Norm and the time you took to post the picture. The 300 water pump is quit a bit different from your 650. There are no gaskets in the 300, only a couple of oil seals, rubber O ring, outlet plate and the cover.

I started to think that the impeller was still slipping again but I tried wedging the impeller the turn the drive shaft by hand. I tried as hard as I could but the shaft would not turn while the impeller was held, so I'm pretty sure it is not slipping.

You're right Merccooper, both my original Mercury factory manual, and an aftermarket manual do not show correct impeller placement for any of lower units.

Sorry I couldn't help you out.
Don

Merccooper,
Your assembly looks correct, impeller, etc, and after reviewing your write-up I find myself struggling for an obvious cause of the problem.
The following are long shots, but things I have come across in the past.
Although the impeller is new, and it sounds like you have restrained it from rotating while attempting to rotate the drive shaft in efforts to see if the impeller key - or pin - is slipping,...Have you carefully inspected the bond between the brass impeller hub and the rubber body? They should be 'vulcanized' together or permanently bonded, but I've come across both OEM & after-market impellers that have failed here.
Another possibility is whether or not the water delivery tube has been bent at some time during assembly attempts, that have left it slightly shorter than it needs to be to properly seal down into the rubber seal in the gear case / water pump area housing. This can easily occur when the lower end of the water tube doesn't get properly aligned - and held in alignment - while the gear case if completely installed onto the driveshaft housing.
Since the water tube has a slight 'Z' in it bends from top to bottom, if the tube is not aligned it can easily and quietly dis-figure and end up too short to seal.
By measuring down into the rubber seal in the gear case to the depth the water tube would seat properly, you can determine how much below the driveshaft housing the water tube should extend.
Although probably not a possibility in your case, there is always a chance the driveshaft has rubbed a hole in side of the water tube about 1/2 way up if the rubber protection sleeve has fallen from position.
The only other thing that currently crosses my mind is whether or not the splines on the driveshaft and in the crankshaft are worn out and not even turning the driveshaft - which of course would result in no water being pumped.
Your parts look so nice and clean, without corrosion, rust, etc that I doubt this last suggestion needs consideration.

Safety note to all: Never grab a propeller and attempt to turn it or the driveshaft while the sparkplug wires are in place. These sweet little 4 cylinder Mercs can start and ruin your day.

I hope these suggestions help, or at least inspire someone else to share another possibility.
I have been known to build a tool out of a dead crankshaft's lower splines, welded to a piece of 1/2" round stock, chuck this took into a gear reduction power drill and spin the driveshaft submerged in a bucket of water with a spare water tube installed to see if the pump will produce enough pressure to lift the water out the top of the tube, then partially block off the flow to see if there is some pressure being produced by the pump.
I should probably build another one of these tools, as I have no clue what happened to the original. Probably tucked away in a forgotten box of Merc Tools - who knows,...Only The Phantom. snicker

Doc

Thanks Don for the confirmation....I read over the manual a couple of times in case I slept through the part about the vanes orientation.

Thanks Doc for all the details you provided and the confirmation of the assembly. I think there is about a 1/2 inch where the delivery tube pushes into the LU. I'll try to confirm tonight. Although I didn't inspect the delivery tube in detail, when I had put it back together, I'm pretty sure there were no dents/rubbing on it. Also, when I did the water test no excess water appeared to be coming from where it shouldn't...but I'll check that again also.
I was trying to think of a way to turn the drive shaft to test. I just may have a leftover crankshaft. I'll investigate that too.
Thanks again.

put a hose and bolt on the top of the driveshaft clamped and run a drill to turn it while it is in a bucket of water and you should see some action.as far as the vanes go. rotating in a clockwise direction the way the motor runs the vanes should trail behind . no matter it will pump either way

Cool idea, I'll give that a try.

So I'm still struggling!
- I've checked out the bond between the rubber and brass hub on the impeller. Looks ok, I'm not able to pull it away or twist it at all.
- The delivery tube is seated by about half an inch into the LU.
- I've attached a hose to the delivery tube and put, what I think to be, very low water pressure. You can see in this video that it does circulate quit well with even the low pressure.
- I tried Dave's idea of using a hose and clamps to run the drive shaft. This other video shows the result of that and I think it shows an expected result. (drive shaft is being turned clock-wise). It is hard to tell in the video, but there is a fair amount of overflow coming back down from the mid-section. I assume this is normal.

When running the engine, NOTHING comes out the tell-tail.
Could there be a chance that the drive shaft is rotating counter clock-wise?
Any other ideas? I'm so disappointed to be stuck on what seems to be such a simple thing!
Link to videos:

You Tube links for videos instead of photobucket. Better quality.

does the motor get hot? the tell tail could be clogged but will not hurt the motor .

Yup, it gets hot.
I put in a new tell-tail coming out from the top of the block as I think Doc and some others suggested. The second video shows the water flowing from it ok when the hose is hooked up to the delivery tube. So, at least I'm sure that one isn't plugged.

Merccooper,

You have pretty well proven that the pump works when turned, water flows through the block when using a hose, and yet the system does not work when running by the lack of a telltale.
Mercury Dockbusters run backwards for reverse and their water pumps have a number of modifications, including check valves, to keep water flowing when running backwards so the possibility exists yours might not pump running backwards.
I have had two strokes start and run backwards on me twice. One was single cylinder dirt bike that was rolling backwards and I popped the clutch to start it. The second was a three cylinder Scott Atwater 60 HP. The problem with that one was that I had mixed up the spark plug wires.
Did you do any work or on or replace the starter? Have you removed and replaced the plug wires?
I agree they are both long shots, but worth checking.
You have a real tail twister with this one.

Don

Thanks for the suggestions Don. I have replaced both the starter and engine block...and have had the spark plug wires off more times than I can remember...or even want to think about about!
I just went out and double checked, when I crank the engine, the fly wheel is turning clock-wise.

I think...just for a try, I'll take the impeller out and flip it over so the vanes are facing the other way. If that doesn't work, I'll order a new impeller. I started thinking, maybe at slow speeds (the speed of the drill in my test), that the impeller doesn't slip, but when faced with the higher speeds/torques of the engine that it just slips.

im kind of new to the mercury motors.. but you just said you replaced the engine block ? is it of the same year and any and all gasket ports the same with water flow???? could the base gasket at the bottom of the motor to lower unit cause any issues with water flow???

Thanks for the ideas, I'll grasp and anything right now! The water flow for this block is the same as the other. The blocks are almost identical. Also, the whole coolant system is very basic on these engines...water pump (pump casing, impeller, drive-shaft), no gaskets....which is (the simplicity of the system) partly what makes this so frustrating!

look at the bottom of the pump cartridge and see if it is bulged up show us a pic of it and the impeller.

You might consider taking your motor / lower unit to the

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Maple Leaf Chaper AGM later this October.

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Gray haired fellows there should be able to solve this for you in short order.

Professor, it is getting harder to find people interested and knowledgeable about these engines!

Dave, pictures, pictures, more pictures and a video... anything that might help...
Hard to tell from the picture, but pump cartridge isn't pluged. I can run water through it without any problem.

Pictures:
s1004.photobucket.com/user/cprs1/library/Merc%20300%20LU%20breakdown

Video:

I'm not able to view the videos - I just see a black square.
But in the photo bucket pictures, it does look like the impeller seen may have been slipping as the 'key-way' appears rounded at its edges.
Have you considered tracking down a later model 'key' since the driveshaft has the flat area for the later style key?
-or-
I don't recall the difference exactly, but if you have swapped parts around on the port side of the block with other similar parts Mercs, you may have restricted the water movement. I recall that once I had an extremely strong & warm pee stream, but the rest of the water was unable to exit. I don't recall if it was a difference in the port side gaskets or the port side baffle plate or cover. It was a first series 500 with the same style water pump as you are working with.
Not sure if the opposite effect in an assembly could result in the power head getting hot though.

If changing the impeller and style of key doesn't resolve the problem, I think it is time to lift the power head and check the placement of the top end of the water tube & its seal, and do some water movement testing from the base of the water tube to the open top end of the water tube, and then a direct pressure with water to the power head's water intake in the bottom of the block to an open tell tale on the top of the block.

My bet is still on the impeller & key though.
Doc

i had an impeller once that had the brass hub was installed a little off center so it was holding the vanes away from one side of the pump body, after grinding it down so that it was recessed it worked fine. just a thought...

Looking at your last video, the drive shaft rotates inside the impeller unless you force it over with the screwdriver. I see that the flat on the drive shaft is worn accordingly. I would go with Docs idea that it is slipping under load. You cannot see the impeller when the cover is screwed down, however, the cover may be holding the impeller firm while the shaft rotates within. I would clean up the flat spot and go with a newer style key. There should not be any play there. The keyway should lock the rotational position of the impeller/

Doc, heres a vid link.


But my take it there is WAY to much slop impeller rotating the DS back and forth.

yes get the newer key. it is flat to fill the space on the DS with the key molded in. also makes it easier to install the impeller doc is correct.

The flat key is an excellent upgrade from the old pin, especially when the flat area is worn.

A few other thoughts:

1) do you have the stainless upper pump plate installed (goes between the pump cover and butts up to the stainless pump insert);

2) it helps to seal the threads of the water pump cover, with Permatex #3 non-hardening Aviation-Type gasket dressing. In one of the previous videos it looked to me like there was water spraying from around the cover threads, when the pump outlet was plugged. A leak around the cover might not let the pump develop enough pressure to circulate water thru the powerhead;

3) a leaking exhaust manifold gasket can blow water out of the powerhead. One way to detect this is (with L/U removed) to hook up water to the copper water tube and run the motor. If you still get circulation thru the powerhead and don't get any water spraying into the cylinders (check for water on the spark plugs), then the problem is most likely in the lower end. Be careful when running with the lower unit removed, it'll want to rev like mad with zero load/backpressure!

HTH........ed

So I went out and bought a new impeller just to remove that from equation.(I have to give a promotional spot to Central Outboard Marine in Toronto. They always seem to have the parts I need. www.centraloutboard.ca ) The impeller on the left is the old one. I used a calliper to compare the inside diameter between the old and new. They are both identical. You can also see in the picture that I have both the flat and rounded keys.

Answering some of the questions:
Dave, I was using the screwdriver to try and demonstrate that the impeller would not slip when I try to turn the DS. The video must be misleading. When you say "clean up the flat spot", do you mean on the DS?

Ed,
1) yup, the stainless upper pump plate is installed.
2) in the test that I showed in that video I didn't have the cover plate tightened all way. I'll take a look at getting the thread sealant.
3)Below is a video showing it running without the LU. (sure was scary to hear it rev like that...didn't let it run long)

So, the consensus is that I should use the flat key and that the flat part of the key goes against the DS?

Not the flat key I was thinking about. I will post a pic of the style we are referring to. I know why you put the screwdriver against the impeller, however, the video shows a lot of slop when you reverse the rotation. The tiny key that you have is rolling back and forth in the flat spot of the DS. The key I am referring to resolves that problem.

OK, went out in the RAIN to get a sample of the key I am referring to, I do not have a complete one, this is one that I had to cut out to get the impeller off the shaft. You can get an idea of the width of the key and on the one end you can see how the pin is molded into it.

Thanks Dave. I appreciate your efforts. It was a nice day here until the rain set in also tonight.
I'm glad I included a picture of the two pins I had. I would have likely assumed the flat one I have was the one you guys were talking about. I couldn't picture how the flat key I had would have worked better but I was going to go along with the experts.

Thanks very much for the picture...makes sense now.

Now, to locate a pin like that. Original part number is C-17-23733 and replacement number looks to be 8M0032837. Hoping the guys that had the impeller will have this also.

28-56662

dave bernard wrote:

28-56662

Looks like it has been superceded by a newer part number, but both old and new are available at many places.

www.marineengine.com/newparts/part_search.php?part_num=28-56662&x=16&y=9


Don't know what the difference is with the newer part, I'd venture to say that either one would be better than the older pin!

The ebay item id given is invalid, no result has been sentThere is a picture of the needed key on an EBAY item.
Below is the link.
doc



If the link doesn't work, just go to EBAY motors and enter 28-56662 into the 'search' box.

Better picture than the one I posted, thanks Thom.

It is not hard to find people with knowledge about these older motors at all.

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The concept of these water pumps has not changed for a long , long time !!!

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The impeller part # of the 1960 motor like yours was also installed in the early 1990's motors.----Common stuff it is.

So I think I'm going to have to admit to defeat. I don't know what else I can do.
I got a new impeller and new "flat" pin.
Below is a video and picture of the installation. Also, another video of a test using a drill.
I have even tried installing with the impeller vanes pointing the other direction. This just resulted in vanes resetting themselves the correct way after running the engine.
I've tried pumping water through the engine using a hose attached to the delivery tube while having the spat plugs removed in order to see if any water was coming from there. Also attached is a picture of the spark plugs. None of them appear to be washed.
I've reconfirmed that there is at least half an inch of the delivery tube that is being seated in the LU when I attach the LU.
I have even checked to see if the prop shaft is turning, just in case by some wied situation the drive shaft wasn't turning!
I have noticed that air is coming out the upper tell-tail.
I'm not sure what else I can do?
Although there might be people around that know the engine, I don't think there are any mechanics that will work on it. I've contacted 4 Mercury shops and each one said no.
New impeller and pin. No slip now:

Pump test of new impeller and pin with drill:

Confirmation that drive shaft is actually spinning!:

Spark plugs:

New pin installation:

see if you have a plug in the top of the power head and remove it and see if it is pumping to there. I see you had no water hose to the motor in your last video. 1 914 310 7086. Dave.

by any chance does that copper pick up tube need to be farther under water?? have you tried just adding a tube to the top of the pump and dropping it a little deeper into the water to eliminate being air bound?????? and seeing if it pumps up... at this point whats a few more minutes going to hurt...

i mean i could be wrong but i was thinking its air bound.. if you stuck a tube into the output hole and dunked the lower unit till the complete pick up tube was submerged and tried it??

Just my 2 cents, but if thats the bucket you have been using, its not deep enough. You need the L/U submerged so the whole pump is in water or nothing much gonna happen.