89 Evinrude 50hp overheat alarm sounds

[starcraftkid]

I picked up a super clean 1989 Evinrude 50hp, the motor has 145 dead even compression, and looks almost new. The first thing I did was stick it in a barrel and test run it. It fires right up, idles great but after a few minutes the overheat alarm sounds. There was a good strong water stream out the back, but the top of the motor feels like its getting pretty warm. I pulled the thermostat and all looked good and it opened up at about 140 degrees when heated in water. I went ahead and installed a fresh water pump kit, new thermostat and while the lower unit was off, I was able to blow air up through the water tube and out the thermostat opening. With the motor running, if I crack open the thermostat cover, I get no water, yet there's plenty of water out the tell tale. If I spray water into the thermostat hole, the motor runs fine and don't overheat. With the leg back off, spraying water up the tube with a hose fills the block and it comes out the thermostat hole.

I'm at a loss at this point, the motor is sitting in a 400 gallon test tank, not on the ears, so it's got real water pressure. The tell tale is strong which tells me the water pump is working fine, the fact that I can blow air down and push water up with a hose tells me there's no strange blockage in the block, and I tested the thermostat in water to be sure. For some reason it still gets hot, it's like its air bound up top somehow. I think I eliminated any other internal motor concerns by spraying water into the thermostat hole and the motor will run cool forever like that.
The odd part is how fast it overheats, it don't even take a full minute of idle time. I tried it with the stat out, and it still gets hot. But if I introduce water from the top, it's fine. I even cut a notch in the edge of the thermostat to try and see if it's getting air bound, that helped but it still get hot, but it takes longer with the notch.
Am I missing something here?

 

[tashasdaddy]

Re: 89 Evinrude 50hp overheat alarm sounds

possible, bad water jacket gasket on head, possible head gasket blowing into cooling system. exhaust gasket, or hole in internal exhaust plate.

it is better to run that size motor on muffs, than a tank. exhaust heats the water fast also.

 

[starcraftkid]

Re: 89 Evinrude 50hp overheat alarm sounds

The tank is over 400 gallons, and has a water circulator to to keep the water moving and cool along with a skimmer to remove oil. It came from an old outboard shop.

I was thinking maybe head gasket or an internal water leak but unless it's got a porous casting, this thing shows no signs of corrosion, none at all. It's like working on a new motor. Even the area inside the thermostat area is clean.
I'm starting to wonder if the overheating issue is why it never got any use.

 

[mrcj001]

Re: 89 Evinrude 50hp overheat alarm sounds

After you run the engine, pull the spark plugs and see if you get "steam" or water vapors coming from the cylinders. Could be bad or incorrectly installed head gaskets and or diverters.

Get one of those cheapo infared laser temp sensors and point it at each cylinder and see if its really overheating and or if one cylinder is hotter than another.

 

[starcraftkid]

Re: 89 Evinrude 50hp overheat alarm sounds

The top cylinder is hotter by far, the bottom of the block stays cool enough to touch, even around the head, but the top of the block and upper cylinder area gets too hot to touch. No water is getting up top from what I can see, no water comes out the thermostat hole if I run it with the cover and stat out. Even with that, I get a good tell tale stream.

It's got me puzzled, it's like the water can't get up that high for some reason.
I pulled both plugs after running, I don't get any steam and both plugs are dark gray or almost black. I'd think that if one plug was seeing water it would be white or really clean?

I really thought it was just a case of being air locked for some reason but I see it's more than that. When it runs, I get no water coming out of the upper exhaust ports like on my other motors, only out the tell tale. It's like the water isn't getting up that high at all?

 

[roxy99]

Re: 89 Evinrude 50hp overheat alarm sounds

Funny thing...not really, I was just diagnosing the exact same symtoms you describe on my Evinrude 140hp 1982 outboard. I put a hose on the lower end tube with the lower unit removed and using a flashlight looked up inside to see where the water was coming from. It was gushing out on one side up need the head yet no water was getting above that level. I made a mistake, I blocked the water flow with a rag and water did make it to the head, except I also ended up filling the piston cylinders with water too! Very odd... Oh, I also found little bits of aluminum in the pipe that comes from the water pump. I then removed the water jacket and exhaust plate. And discovered a 1 inch hole in the exhaust plate...I guess the engine ran dry and a hole was burnt through the plate on one side from the hot exhaust!

I just spent a few hours welding the hole, grinding it smooth to repair it... too bad these engines don't shut off automatically when there is no water pressure in the block!

 

[Haffiman]

Re: 89 Evinrude 50hp overheat alarm sounds

Is the 'pee' hose from exhaust cover going over the top of the cylinder and then down, or routed straight to the outlet?
It may even look like it is over cooling at the bottom or not running persistently on both cylinders.
Perhaps time to take down the head and change the head gasket.

 

[starcraftkid]

Re: 89 Evinrude 50hp overheat alarm sounds

Is the 'pee' hose from exhaust cover going over the top of the cylinder and then down, or routed straight to the outlet?
It may even look like it is over cooling at the bottom or not running persistently on both cylinders.
Perhaps time to take down the head and change the head gasket.

The tell tale hose goes over the top in what appears to be the factory clips.
Its running fine as far as I can tell in the test tank. I've not had it on a boat yet, but the test tank is pretty large, over 500 gallons.
I did try a new head gasket, no change, and all looked fine inside as well.
It still acts like it's air bound.

I'm mainly at a loss as to why the water won't get up to the top of the block. I am considering gutting a thermostat and trying it that way, just to see if it is air bound somehow.

Does anyone have any ideas as to why they changed the head and thermostat design on these motors after 1987? It sure does make getting the head off easier, but I'm not convinced in this style of thermostat right now.

 

[Aratsman]

Re: 89 Evinrude 50hp overheat alarm sounds

Double check your water tubes out of the pump. I just had a similar problem on an older motor. Check to make sure that the grommets are not folded over restricting water flow. I have read many other posts over swelled deflectors in the head causing lack of water flow.

 

[Haffiman]

Re: 89 Evinrude 50hp overheat alarm sounds

If the tell-tale hose goes on top of the cylinders, the water height inside block should be the same.
If not, water is leaking 'out' at a lower level.
Pull the head!

 

[starcraftkid]

Re: 89 Evinrude 50hp overheat alarm sounds

If the tell-tale hose goes on top of the cylinders, the water height inside block should be the same.
If not, water is leaking 'out' at a lower level.
Pull the head!

I had the head off, everything looked minty clean and perfect.
I would think that if I had an issue with the water pump tubes I wouldn't have such a strong tell tale stream. The telltale outlet comes out the side, the hose loops over the back of the cylinder head and down to the pan connector. If water was leaking into the combustion chamber, the motor wouldn't run as good as it does. It's also a low hours freshwater motor, even the paint on the lower unit and prop are still perfect.

The guy that had this swears it never overheated or set off the alarm, it was given to me by a buddy that gave up on boating due to age, the motor sat in his garage under his house since 1992 unused. The controls are not from this motor, their from the boat it's destined to be put on once I get this straightened out.

The dealer hear told me that the newer motors, after 1987 had problems with cooling and that there's a water passage that clogs up beneath the power head. They said that this version of the motor was short lived for several reasons, one being cooling issues, the other being the tilt/ trim piston failing and costing over $1500 to replace.

The part that I don't get is that if there's water pressure at the tell tale tube, there should be water at the thermostat area. The tell tale has a lot of pressure, if I pull the hose off, it shoots water about 10' across the shop. If I loosen the thermostat while it's running. There's no lack of pressure. Why wouldn't the tell tale come off the top of the motor vs. the side cover?

If there was no outlet for the water on the outlet side, that would explain why I have pressure and not flow. I get nearly no water coming out the upper exhaust reliefs compared to my older 55hp.

The tank I have is huge, I can run bigger motors for hours without a temp increase, so I don't think that's an issue here, besides, it sets off the alarm way too fast.

 

[Haffiman]

Re: 89 Evinrude 50hp overheat alarm sounds

The tell-tale outlet is on the exhaust cover before water enters the cylinder area.
Did you check the channel from exhaust to cylinder when head was off?
Sure nothing was 'nesting' there after the long storage?

 

[starcraftkid]

Re: 89 Evinrude 50hp overheat alarm sounds

The tell-tale outlet is on the exhaust cover before water enters the cylinder area.
Did you check the channel from exhaust to cylinder when head was off?
Sure nothing was 'nesting' there after the long storage?

Everything inside was spotless, almost too clean, not even water stained.

I tried something today, I pulled the lower unit back off, plugged up the water pump tube from below, plugged up the tell tale tube, and added water through the thermostat opening, it took several minutes for the water to drain back down through the exhaust tube. I would have expected it to run right through?
( I also did this with the plugs out to again verify that no water was getting into the cylinders). I'm starting to think my first thought about it being air bound may be the case but for a different reason. For some reason the water isn't getting out of the block fast enough, therefore it's not circulating and cooling the motor properly, and possibly letting the top of the block, above the tell tale to get air bound?

Does this make any sense?

I think my next move is to pull the power head and take a look at the lower water and exhaust outlets?

 

[Haffiman]

Re: 89 Evinrude 50hp overheat alarm sounds

As no water came with thermostat out, probably not an air pocket in cylinder channels.
Take off the exhaust cover.

 

[starcraftkid]

Re: 89 Evinrude 50hp overheat alarm sounds

As no water came with thermostat out, probably not an air pocket in cylinder channels.
Take off the exhaust cover.

I've had the side cover and head apart, nothing in there looks bad or clogged. In fact it all looks pretty clean. No corrosion, no mud stains, no discolored metal, just clean aluminum casting.
Maybe it's not a matter of it being air locked, but a case of it just not being able to move the water?

I called another dealer today, they also said I most likely need to pull the power head, apparently these had issues with the exhaust outlet passages?
This is the third dealer to tell me basically the same thing, and the second that said they weren't interested in even working on it. (Too old).

If I get home early tomorrow I'll start on pulling the power head off and get a better look, at this point its the only place I haven't been.

 

[Haffiman]

Re: 89 Evinrude 50hp overheat alarm sounds

Before removing the power head I would have done the following.
remove gearcase and attach a water hose to water tube.
Remove thermostat and put on pressure.(keep the cover off)

Water should come immediately to thermostat.
If not, down with head and check all channels!!!
That is a 'lost-foam' casting head and it might be a casting error inside the head.

 

[starcraftkid]

Re: 89 Evinrude 50hp overheat alarm sounds

Before removing the power head I would have done the following.
remove gearcase and attach a water hose to water tube.
Remove thermostat and put on pressure.(keep the cover off)

Water should come immediately to thermostat.
If not, down with head and check all channels!!!
That is a 'lost-foam' casting head and it might be a casting error inside the head.

I did that. With the lower unit off, I actually clamped a garden hose to the water tube. With the thermostat out, water pours out the thermostat hole and the tell tale hole. If I plug the tell tale, and the thermostat hole with my hand though it builds pressure? Like the water can't get back out? I did something similar on another motor here, not an OMC, and the water just poured back out the exhaust housing, I'd have expected the same here?
I took out the spark plugs too, but no water in there. It's like the water can't get back out of the motor. If the pump is pumping against an air pocket I doubt it will cool properly? Is there someplace that can get clogged up easily that would prevent the water from getting out?

 

[Haffiman]

Re: 89 Evinrude 50hp overheat alarm sounds

It might not be going out of the head from thermostat, it might be blocked from head through exhaust collector.
In both cases you need to remove the head to find the blockage.

 

[boobie]

Re: 89 Evinrude 50hp overheat alarm sounds

After all you've done I'd say pull the power head and look for something in there.

 

[omcgreasemonkey]

Re: 89 Evinrude 50hp overheat alarm sounds

pull the power head the exahust at the base has had a issue there blow it all out with air youll be fine and ohhh those shops said too old theyd hate the 1950's and 60's motors i still fix for people