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

[steamin53]

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.

Today 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.

I can tell when the thermosat opens as 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.

Steve

 

[reelbad]

Re: 72 Evinrude 50hp overheating

Re: 72 Evinrude 50hp overheating

have u tried flushing the block take the thermostat out and start the motor and let it run for a couple of mins and see what comes out of the motor

 

[tashasdaddy]

Re: 72 Evinrude 50hp overheating

Re: 72 Evinrude 50hp overheating

as above said, also they really do not like muffs. the like a big barrel, or the boat ramp. you also may have crimped the grommet, where water tube goes into water pump, this will restrict or block flow.

 

[steamin53]

Re: 72 Evinrude 50hp overheating

Re: 72 Evinrude 50hp overheating

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.

I'd still like to know if the head can be removed for inspection of the water passages without removing the water jacket cover.

Your help will be greatly appreciated.

Steve

 

[F_R]

Re: 72 Evinrude 50hp overheating

Re: 72 Evinrude 50hp overheating

Of course the head will come off without removing anything else. I would have to check to see if it has water deflectors or not. They are just pieces of hose. They are visible after removing the head.

I think you should put it in the water and see if it cools before doing all that work. That cooling system shouldn't get plugged up in fresh water unless it swallowed a shattered impeller or something. Now if it overheated to the point of burning gaskets and stuff, that is a different story.

 

[steamin53]

Re: 72 Evinrude 50hp overheating

Re: 72 Evinrude 50hp overheating

Thanks for the reply. Judging from the condition of the thermostat gasket, the plastic pressure relief valve and it's grommet I must conclude that this engine has not been hot in the past.

It's on a stand right now and I agree that the best next move will be to run it with the lower unit submerged. If it continues to overheat then I'll move to removing the head.

I'll post back the result.

Steve

 

[mikesea]

Re: 72 Evinrude 50hp overheating

Re: 72 Evinrude 50hp overheating

its not uncommon to get water out thru the upper reliefs on muffs,when the eng is submerged ,you get a backpressure that restricts the free fall water,as mentioned,put in the water before you do anything else,unless you removed the head ,and deflectors,they are likely OK if you indeed have any,on a 50 im not sure,DID you encounter ANY debris in the aterpump installation? sand ,old weed,it dont take but a few grains of sand to screw up a thermo,BUT,if you replaced it ,that should not be an issue,have you inspected the intake screens in lower unit,are they clean,rn the eng with the thermo cover off and see what kind of flow you get,

 

[steamin53]

Re: 72 Evinrude 50hp overheating - I'm flat out of ideas now!

Re: 72 Evinrude 50hp overheating - I'm flat out of ideas now!

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

 

[F_R]

Re: 72 Evinrude 50hp overheating - I'm flat out of ideas now!

Re: 72 Evinrude 50hp overheating - I'm flat out of ideas now!

Well, even if everything else is ok, you would have problems acording to your first sentence there. 1/2" below the cavitation plate is nowhere near deep enough. The water needs to be well up above the water pump location. 6-8" above the cavitation plate would be more like it.

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

 

[steamin53]

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

Thanks for the reply F_R. I figured the water level was above the inlet screen that feeds the pump and the drain holes in the case. In fact, when I goosed it a little with the carb linkage I did finally get a tiny bit of water surge from the vents just below the power head.

Gosh I wish this was on a boat and not on a stand. I'm finding it almost impossible to find anything large enough to accomadate the entire gear case and trim vane and still be deep enough to submerge as you've suggested.

I may well be wrong here but I thought that the vent or grill like openings on either side of the leg that are above the cavitation plate were drains. If the are, I wonder if I again submerged it as described and closed them with duct tape if it would "simulate" being so submerged by blocking any possible sucking of air into that point?

I know on my 250 Yamaha it's necessary to tape closed drain openings on the lower unit to be able to run it on muffs.

Your take on this?

 

[tashasdaddy]

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

big garbage can. bring water 1/2 way up leg. you are not going to get a lot of water flow out the exhaust relief, most goes out the prop. you will get mist and droplets at idle, it will pick up at higher rpms.

the slotted vents on the side of the lower unit are the water intake pickups. do not cover.

 

[cougar1985]

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

hope i can be of help here.i have a 1970 33 hp evinrude that i replaced the pump on a couple of years ago.much to my frustration it would not pump water ,so tear apart ,do again,and again ,and again.well i was getting pretty frustrated and did everything but still wouldnt work properly ,even changed the friggen housing!ive change enough impellers to know something wasnt kosher so i sat and though for a couple of beers and decided to try something.i coated the bottom of the impeller housing with avation gasket sealer(brown gunky stuff) and the surface of the other mating surface,i assembled and tried again.presto ,a good misting motor ,so much so that i was very impressed and now use it all the time.it works trust me .i assume it seals up inperfections in the mating surfaces that may not give a proper seal and maybe you dont even notice or see them.

 

[mikesea]

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

Steve,you tried the muffs,it overheated,could have been due to the volume of water,and or the configuration of the engine not allowing enough water flow,you said the thermo.was found to be problematic.So I think that was PART of your problem,NOW,unless your lowerunit is submerged BELOW the waterpump assy.you will likely encounter problems,reason is,the pump isnt the best at pulling water up because it gets no prime,if the water is below the cavitation plate,the pump is not submerged,Now,I HOPE at this point ,the pump wasnt run dry while trying to SUCK water up thru the intake screens,In a perfect world ,with a perfect pump assy ,MAYBE it will suck it up,but I have my doubts,thats why they suggest you totally submerge the lowerunit in a barrell etc.If you did fix the original overheating problem,I dont see why your engine shouldt get water in ample supply to run for at least 5 minutes on a hose.But,are you getting a good flow of water from the hose,Its not a gravity feed line from a well or the like is it?If you have a good pressurized water system,moffs fit right ,you should not have a problem.Now,if we assume the pump is OK,why wont you get water out of the thermo cover,when running?that would indicate some kind of restriction in the workigs between top of pump and to the eng,could be something in the watertube,or engine block,the best way to check would be ,directly put water frome a hose up the water tube with the lowerunit off,if water passes up that water tube ,out the thermo cover that is removed,you have a problen in the pump assy,which could be a impeller that burned up in process of trying to get water ,water is its lube,15 seconds of rubber friction will fry it,if water wont go up the water tube ,I would pull the head and continue looking for blocked passages.Reply back with any findings.Mike

 

[steamin53]

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

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

 

[steamin53]

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

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