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72 Evinrude 50hp overheating - HELP! I'm sinking here!

S

steamin53

Member
I recently purchased a long stored fresh water only 1972 Evinrude 50 hp model 50273C.

We changed the water pump as a result of the overheat alarm sounding after 5 minutes at idle on initial start up. It still sounded the alarm after the replacement of the pump.

Below is a summary of the troubleshooting to date as posted on http://forums.iboats.com/showthread.php?t=379974.

I pulled the water jacket cover on the back and changed the thermostat which when tested did not open at the correct temperature. I also tested the replacement thermostat which functioned correctly. In addition, I replaced the "poppit" valve grommet. The valve was ok.

The unit still sounds the alarm. A temperature check of the head at the time it sounds the alarm (around 4 to 5 minutes at idle on the muffs) shows the temp to be 102 deg. Centigrade (215 deg. Farenheit) which per my clymer manual is the appropriate temp for the sensor to close and power the alarm horn.

Just prior to the alarm the water flow from the hub increases and steams. There is no tell tale trace on this model engine. As a result I "think" the pump is functioning correctly. I do not see any water coming from the upper vents at the top of the exhaust housing just below the engine.

My question is NOW WHAT??? Could it possibly be that this engine will not run on ear muffs? As I recall I had a similar year model about 30 years ago and ran it on muffs but I'm not certain.

Can I pull the head without removing the water jacket cover to check the cooling passages? Just where do the cooling passages run?

If anyone has a coolant flow diagram for this engine I would sure be grateful if they would post it for me.


Update

Thanks for the replies guys. I'll try removing the water jacket plate and the thermostat again... (it's a PIA). I do note that I have yet to get any water out of the upper vents on the exhaust housing. Is that significant?

Also, in other threads there is mention of water deflectors perhaps being the problem. I can't locate that item on any evinrude parts list. Does anyone know the evinrude teminology for those parts or even if they are applicable on this model engine?

I will say that the top of the head and the passages for the pressure relief valve and the thermostat were nice and clean when I had it off and showed no evidence of corrosion.

Update

I ran the engine with the lower unit submerged up to about 1/2" below the cavitation plate. Still overheating.

I again removed the cylinder head cover to confirm the thermostat in place and it was so.

I removed the thermostat and the pressure relief valve and started the engine on the hose muffs. As expected it still overheats.

BUT NO WATER IS PUMPED UP TO AND OUT OF THE THERMOSTAT OR PRESSURE RELIEF HOLES.

Keep in mind that the water pump impeller was replaced by a local shop prior to my first start up of this old engine. An outboard salvage yard here locally with a grizzled ole hand who's been at this for 30+ years says that if the impeller plate were installed upside down the pump would move some water but not enough to cool the engine.

The shop that replaced the water pump states that the impeller was not broken into pieces but had a rigid set to the blades so it was replaced. They insist that they could not have installed the impeller plate upside down since when on the muffs if the engine is reved above idle the pumps sucks in the overflow from the muffs. They say that the problem is perhaps the gasket or o-ring where the water tube enters the bottom of the engine.

In going over the Evinrude parts list for this engine I see no such gasket.

HELP HELP HELP - I'm sinking here!


Steve
 
To my knowledge, drawing on memory, it's impossible to install a water pump plate upside down..... the screw holes would not line up.

Running on a flushette, for a engine of that horsepower..... hose pressure must be turned on full force.

In the water or a barrel, the water level must be a few inches higher than the joint area of the lower unit/exhaust housing (top surface of the lower unit) so that the water pump is completely submerged...... not simply over top of the cavitation plate. A low water level at idle can (and usually does) cause the water pump to draw air.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store
 
Any chance the one end of the tube connecting the pump to the powerhead isn't in the right spot? that would cause the water to dump into the exhaust housing instead of supplying the powerhead with cooling water.
 
A known problem, at least on the somewhat later models, was the upper grommet on the water tube.
That grommet was replaced with 2 plastic washers.
se pos95
 

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Thanks for the input men. I find compression to be 150 and 135 on the two cylinders. I'm holding out on removal of the head until the last resort.

I have located a taller container in which to run the engine in water submerged above all vents and drains. That's going to be step one.

I can't seem to open the pic posted in regard the the upper grommet on the water tube being replaced with washers. Can anyone post it as a picture that can be viewed without linking to it, or perhaps email it to me?

Steve
 
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Thanks for your reply Haffiman. Unless I'm mistaken if the compression is within 10% between the cylinders it's acceptable. Are you stating you feel it's a problem as is?

150 psi less 10% is 135 psi.

I have checked the Evinrude manual for this motor and can not identify even the grommet for the outlet end of the water tube. Can you give me a part number for either the grommet or the plastic washers you refer to?

Steve
 
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Struggling somewhat with the new board format, but will manage sooner or later.
Go here:
http://epc.brp.com/SiteMods/BRP_Public/BRP_Public_Login.aspx?ReturnUrl=%2fIndex.aspx
Then follow instruction and you will find your engine.
Look under :exhaust housing
If you are going for the grommet, you are in for a major tear-down anyway as power-head must be removed.
Then might as well split it and check!
If a problem?
135,0-150,0 you are just at the tolerance.
134.9 - 150,1 you are outside.
Edited:
The grommet shown is the original, but if ordering through a dealer, you may get the new one, What is important is to order 2! Long time ago it was a service bulletin on this matter
 
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Thanks for the quick response Haffiman37. You are correct about the compression.

I happened to be on the BMC site as your reply came up. Interestingly the grommet is not shown on the 1972 50 hp model. I was looking at the time at a 77 70 hp and it does show a grommet. I wonder if they are the same part.

I'm prone at this time to suspect that I may not have had the water level high enough in the container I was using and next will try one 2 inches deeper and may even form increased depth with some plywood and line it with some plastic sheeting to hold the water even higher.

I'm obviously stuggling here to find the simple explanation as I'm prone to always suspect the worst case only to find later that it was something much simpler.

Steve
 
The 72-50 has a grommet, bu you have to look at the bottom of the water tube to find it!
Screw -retainer-grommet.
Copy the diagram to your comp, 'open with': windows pic &fax, expand.
gets a bit unclear, but clear enough.
If running in a barrel, water level should be about 1" above the lower unit/leg split as min.
 
check for pieces of that old grommet in the water jacket groves and old impeller vanes that probably r causing blockage in the head
 
Thanks for the information guys. I was advised that the impeller was intact on removal. I will be able to raise the water level that high or higher in my next test. So far NO debris has been found.

Haffiman are you referring to the grommet on the pump... at the bottom of the tube? I thought you were referring to one at the top.


Steve
 
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The grommet shown at the bottom of the tube in the 'exhaust housing' section is the one that when properly installed is at the top!!
Grommet is pushed up, then retainer is fixed with the screw to the exhaust housing holding the tube to the exhaust housing.
For the pump grommet, look at the gearcase section.
 
The 'naughty' way to test , is to remove the gearcase, hook the water hose straight onto the tube and start!
You may even get an indication by putting water pressure on and see how big 'resistance' is for water to flow. If thermostat is removed, close to 0 resistance.
 
SHE LIVES!

First of all let me thank every one of you men for your help. I really appreciate your taking time to advise me. Evinrudes are not my forte! Now I've done some pretty good Yamaha work for a novice...but not evinrudes.

I finally found a rubber maid storage container narrow enough to fit between the legs of the stand and tall enough to cover the vents above the cavitation plate on the leg lower unit. I removed the plugs and cranked it with the head cover off and thermostat and pressure relief valve removed. No water was pumped out of the thermostat hole in the head but I did note water running down over the lower mount bracket on the front of the leg so I knew the pump was moving water. Just on an off chance I installed the plugs and cranked the engine. After a few seconds I got a flow from the thermostat opening as well as from the pressure relief valve and a (what I would consider) strong flow from the aft vents on the leg below the power head. I ran it that way for a spell with no debris evident in the outflow and once convinced it was moving water to the power head I reinstalled the thermostat and pressure relief valve and head cover.

She runs great (well pretty good) but no overheating in more tham 10 minutes of run and I still have a good continuous flow of water from the vents below the power head...even at idle with the throttle plates completely closed. My IR thermometer indicates cylinder head temps of 155 and 158 deg. F. after 10 minutes of running so it is cooling well.

Who knows, maby I moved some hidden debris from a passage and just didn't notice it being discharged (very likely if it came out with the exhaust).

I will do one more test. That being cranking the engine on the muffs with plugs removed to observe whether I still observe water flowing over the lower mount bracket which would indicate that the pump is indeed moving water up the tube. If so I may start the engine for a brief moment to observe discharge from the vents at the top of the exhaust housing. That would prove I've opened the passage somewhere and "healed it".

But a couple of questions remain.

1. It seems to me that when on plane the passages on the side of the leg that lie above the cavitation plate would perhaps at least partially be exposed to the air. Almost certainly they would if trimmed/tilted up high enough to load trailer or operate in shallow water.

2. Should I be concerned with the water discharge that was flowing over the lower mount bracket ? It occurs to me it could indicate a bypassing upper water tube grommet that might not present a problem until operating at high rpm on the water. What's your take?

Steve
 
As for 1.
Should be no problem, they are relief and drain only. Not in the 'suction' side of the pump.
As for 2.
Pulling the gear case and attaching a hose to the water tube will tell if leakage on pressure side. Any leakage on pressure side will result in loss of cooling capacity.
 
Well the final test shows that yes it moves water on the muffs as observed in the flow over the lower bracket mount but still wants to overheat on the muffs.

Most curious. I can't understand why it doesn't move enough water to cool it on the muffs but does when simply submerged above the cavitation plate. I'm almost certain my engine years past of the same vintage ran fine on the muffs. 40 PSI water pressure to the muffs seems like it should do it. It is afterall enough to prime the pums because water is moving up high enough to drain over the lower bracket mount.

I'll bet money the upper grommet is bad.

Steve
 
"2. Should I be concerned with the water discharge that was flowing over the lower mount bracket"

Not sure exactly what you mean by that. Can you post a pic. There are places where water will abnormally flow if the pump isn't hooked up correctly.

My guess is the water tube is pinching the rubber grommet at the pump, or the the center seal/grommet in the pump is missing.

Time to drop the lower unit. As was stated earlier, you can then hook a garden hose directly to the water tube. I'm betting your flow will be fine.
 
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