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73 50 Evinrude No Water

bill_w

bill_w

Advanced Contributor
I fired up my 50 Evinrude for the first time in 2 years. Running on the muffs, I didn't get any water out of the exhaust ports. So, shut it down, pulled the lower unit, stuck the hose onto the water tube to blow out any critters, flushed out intake ports to do the same, then replaced the impeller. Started it up on the muffs again, still no water out of the exhaust. If I hold the muffs on tight by hand, I get water out. Anyone have any ideas??
 
I tried this again, and I'm still not getting water out of the exhaust ports unless I actually pressurize the cooling system by holding the muffs on tight. When I put the garden hose onto the bottom of the water tube with the lower unit off, I still don't get much water if any out of the exhaust ports. Could the thermostat be plugged/blocked? I tried running it after I changed the impeller, and the warning horn went off after a few minutes of idle.
 
I'll check the thermostat. I haven't pulled it yet. Testing it in the lake is a hassle for me...I can get it in at my place, but I need a tow boat, 2 people, 10 miles to drive to get it out. So, I like to make sure it's good before I launch.
 
I pulled the head cover, and pulled the thermostat...looks ok, not broken. Tried running it with the thermostat out, and head cover off. Still no water out of thermostat hole unless muffs held on tight, to pressurize the cooling system. Pulled the lower unit again, checked to make sure that the impeller is in the right way, and the keyway was there, and the intakes were clear. All ok, tried again, still nothing out of the thermostat hole???? Pulled l.u. again..hooked garden hose to bottom of water tube..very little flow from thermostat hole. Tried coathanger to unblock water tube, can't feel/find any blockage. Tried to flush from thermostat hole down. Nothing/little from water tube. Something is blocking it somewhere. Any suggestions, other than pulling the block off..I really don't want to have to do that.
 
With the lower unit removed, try immersing it in a bucket of water and using a cordless electric drill to spin the shaft clockwise to check for proper pump operation....if the shaft is too big to fit in the chuck, use a rubber hose that fits tightly over the shaft on one end and use an adapter on the other end which would be compatible with your drill chuck...clamp the hose at both ends with stainless steel hose clamps....use a piece of copper tubing to direct the water so you do not get a bath. A piece of a broken impeller can often clog small passages.
 
I don't think the pump is the trouble..I think its up in the engine block itself. If the garden hose at 50 psi won't push water through the block, the pump sure won't. And the old impeller looked fine to me..no broken pieces, in fact still 100% flexible and useable. Original 1972..the lower unit had never been off before. Maybe I'll try some thin wire and try and feed it thru the thermostat hole..see what happens.
 
If you replaced a stuffed impellor recently there may well be old rubber bits either in the tube from the pump or, most nasty, rubber bits in the water gallery in the bottom of the block.

Pull it apart fully and check.

B
 
You are in for quite a job.
Upper water tube grommet needs to be replaced (by 2 plastic washers!)
Off with power head and exhaust adapter.
 
Old impeller was fine..I'd have no problem with re-using it. Still flexible, no missing pieces. Whats with the grommet? Swollen and blocking the water flow? Bottom one is okay, not cracked, hard, anything like that. Why does the top one go bad? Heat? This one was fine when I stored it 2 years ago.
 
Haff...are the plastic washers a replacement item? I checked the parts diagram on here, and the grommet is listed. I think I found out where my mystery bolt came from..the grommet retainer. When I pulled the lower unit, a loose bolt came with it. I thought the grommet went around the water tube, and sealed the connection, Why/how can it block it? One more thing..when I had the water hose on the water tube, I could hear the block filling up, then the pressure began to build. Sounds to me more like a blocked passage in the block somewhere.
 
Was a service bulletin some decades ago changing the grommet to 2 washers. If you order on the old part number, you get a cross-over to the new washer. However remember to order 2!!!! The old grommet gets squeezed by time and flow-trough severely limited.
 
Studing the parts diagrams and listings here..looks like OMC changed from the grommet to washer style seal in 1977, on the 55 hp. So, I'll take a shot and order the 77 washers.
 
I believe the numbers are 0332363. You find them in 1993 -45 HP on the Evinrude.com web site. Listed as quantity 2 pr engine.
 
Is there no way to change the grommet and install the washers from the bottom. Long socket extension and a flashlight maybe? Or is the exhaust tube in the way?
 
Only if you have a trained cobra that may handle a socket and ratchet and at the same time hold the pieces in place.
 
Hmmmm.. I'll have to look into Cobra training in my area. And I assume minature sockets as well..need soft handles for the fangs to get a grip.
 
Ok...took off the LU again...took off the powerhead. Not as bad as you made it sound Haffiman. Now I have more questions lol. The water tube is not blocked, so no bad grommet. But, water will not flow thru the powerhead, unless its under pressure. I tried it both ways, using the garden hose, pushing water into the inlet, and also pushing water into the outlet. Same both ways. It seems like there is something in the powerhead stopping the water flow. Am I right in thinking that it shouldn't take say 20+ psi to push water thru the powerhead?

Next question. What is the spring loaded "thingie" located above the thermostat? What does it do? When I pulled out the thermostat, I saw that the rubber grommet it fits into was distorted, so I replaced the grommet.

I'd really like to get this unit back in the water after it's two year rest. It starts great, runs great, pushes the 15' fiberglass runabout at 30 mph, just won't cool anymore.

thanks,
Bill
 
The power head might not be the worst part, but the exhaust collector below it. Pull down the exhaust cover and check water passages. If ok, pull the head. Somewhere something is blocking, it should be 'free' passage to the thermostat. However if thermostat is installed (cold engine), you have to overcome the pressure of the relief valve - 20-30 PSI!
 
I did look at the exhaust collecter, and was thing about pulling it. But, I ran water through every opening/passage I could find, including through the exhaust cover (with it off). Water runs everywhere, without seeming to be blocked. The thermostat is installed, and testing is on a cold engine. So, the pressure I'm getting trying to get water through the block is because of the pressure relief valve? I didn't think the water pumps on outboards were designed to be pressure pumps, but volume pumps. If thats the case, could it something as simple as a bad grommet at either the bottom or top of the water tube, letting the water pressure drop because of leakage? The impeller is new, the impeller housing looks like new, the stainless plate below the impeller has some minor scoring, but nothing major.

How about if I pull out the pressure relief valve? How about it and the thermostat? What the heck purpose does the pressure relief valve serve? Does it allow water to by-pass the thermostat when the thermostat is closed? Stupid question, of course it does.

I'm running out of boats...115 dead or dying, 50 not peeing, 1965 50 Merc is a longshaft, running on 3 instead of 4, not putting it on the sidewinder, so I'm down to a 16' aluminium with a 1977 20 Merc......Hmmm...lot of potential scrap value here. Price of scrap aluminium is pretty high right now.:eek:
 
If you can get the front engine mount off the exhaust collector, I would have taken it off and changed the grommet to the washers!
At low rpm, the thermostat controls the engine temp and enough water gets through. At higher rpm's the water is partly bypassed the thermostat due to pressure, the engine temp might DROP, allowing more fuel to be burned(similar to choking a cold engine) = higher performance! The thermostat itsel does not have enough by-pass capacity at full power to cool, but if increased it will be too inaccurate at idle. However the thermostat must have a 'bleed hole' to let air out. If completely tight when closed, water will not be able to get to the thermo element. Have seen this problem on some aftermarket thermostats.
 
I bought an OMC thermostat...no air bleed hole, I looked before I installed it. The original had one, and I wondered about the new one not having one. I was looking for it because I thought it would install like a car, with the air bleed hole up. So, the pressure relief valve allows water to bypass the thermostat at higher rpms. If I take out the pressure relief valve, water will bypass the thermostat, resulting in a colder running engine. Cold engines are not good, fuel doesn't vaporize properly, or burn properly.

I will take off the exhaust collector, and replace the grommet with the 2 washers. I haven't put it back together, its still all apart. I will change the pump end grommet at the same time. If this doen't work, I'm going to pull the thermostat cover off again, and try it without the relief valve. At the same time, I'll drill a hole in the new thermostat the same size as the one on the original.
 
Some of the thermostats does not have a hole, but a 'slot/jack' in the top disc allowing air out or the disc does not fully seal, but stops just short of sealing when 'closed'.
 
There is a small slit in the disc...maybe thats the bleed? I won't have this back together for about 2 weeks...I'll update when its done. Thanks for the help so far.
 
All back together again. Removed the exhaust collecter (NOT fun), changed grommet to washers (grommet was good), changed lower water pump grommet (it was good), new gaskets, etc. End result is the same, no water from the exhaust ports, engine still overheating. What happens if I pull the pressure refielf spring, or cut it to lower the pressure needed to bypass it? I'm not gonna pull this thing into pieces again. I'd rather sell it as is to someone, than go through that again.

I double checked the water pump housing before I put it back together, it looks good, no cracks, triple checked the impeller rotation direction, compared the old and new impellers, to make sure they were the same. I'm out of ideas, and frustrated as hell.

Bill
 
Your engine does not originally have a pee-hose, install one!
Either on top of the block where water enters the cylinder, or high on the exhaust cover.
How is the big rubber seal between the gearcase and leg?
If cracks or leaking, exhaust may enter the pump.
 
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