1975 Evinrude 115hp Pumping Water

[Markoku]

Hello,
I've recently come into a 1975 Evinrude 115hp outboard. This motor had not been started since 1996. I got it started (cleaned carbs, new sparks) and it runs great now. I'm new to Evinrude's, but I'm conceded that it might not be cooling the heads. I know that this motor does not have a tell-tail, but it?s my understanding that water should come out of the two exhaust ports directly below the powerhead. Right now, a very fine mist comes out, nothing like what gets pumped out of my 1965 18hp Evinrude Fastwin. I have replaced the entire water pump and housing. And when I disconnect the water lines into the heads, water is now pumping (hard). I?m just unsure how much water should be coming out of the exhaust ports, if any at all. I might be over thinking this, but I just don?t want to get out on the river and seize the motor.

Thanks for the help.

 

[racerone]

A very fine mist comes out , that is correct.

 

[F_R]

For one thing, you can't compare it to an 18. In the first place, it has a thermostat-controlled recirculating cooling system. Briefly, that means that when the 'stat is closed, the water is returned via a second tube to the pump for recirculating. Then when it is warm enough, the 'stat opens and water is discharged and replaced by cool lake water. The important thing is that the 'stat is constantly sampling the water temp and opens and closes as required to maintain the desired temp.

Having said that, even if the 'stat is closed and in recirculating mode, some water is discharged to keep the exhaust system cool. That "some" water (or a portion of it) is the slight spray you see. When the stat opens, you will see a heavier spray. Saying again, it is not an either-or situation. The process goes on constantly. And at slow speeds with cooler/colder lake water, it may never get warm enough to open at all.

 

[F_R]

Back to the 18, if it is new enough to have a thermostat, they have a very different system. They have two water routes through the powerhead, one controlled by the thermostat and the other in free-flow all the time. That is why it gushes water out the relief port all the time it is running.

 

[Markoku]

For one thing, you can't compare it to an 18. In the first place, it has a thermostat-controlled recirculating cooling system. Briefly, that means that when the 'stat is closed, the water is returned via a second tube to the pump for recirculating. Then when it is warm enough, the 'stat opens and water is discharged and replaced by cool lake water. The important thing is that the 'stat is constantly sampling the water temp and opens and closes as required to maintain the desired temp.

Having said that, even if the 'stat is closed and in recirculating mode, some water is discharged to keep the exhaust system cool. That "some" water (or a portion of it) is the slight spray you see. When the stat opens, you will see a heavier spray. Saying again, it is not an either-or situation. The process goes on constantly. And at slow speeds with cooler/colder lake water, it may never get warm enough to open at all.

I assumed that if I removed the water lines after the thermostat (I disconnected them at the heads) and water was being pumped, then the thermostat is good. Is that the case? Or is there another test, short of pulling out the thermostat completely, to see if its working. I'm getting the mist out of the exhaust ports, and I let the motor idea with ear muffs until it came up to temp. But I never got more then mist. All that being said, when I did disconnect the water line to the head, the water that came out of the head was very hot, like almost burning my hand.

 

[F_R]

That water coming out of the heads is before the thermostat. So, possibly the thermostat is not opening in response to it. Worth a test anyway. Yes you have to remove it to test it.

But before getting too angst, maybe you should launch the boat and make sure you really do have a problem. Running on muffs is not a good test.

 

[Markoku]

That water coming out of the heads is before the thermostat. So, possibly the thermostat is not opening in response to it. Worth a test anyway. Yes you have to remove it to test it.

But before getting too angst, maybe you should launch the boat and make sure you really do have a problem. Running on muffs is not a good test.

Good point, my only concern is that if there is a issue, I won't know until its to late. And I'll do some type of damage to the motor. I don't think my boat has any kind of over heating warning. What kind of damage will over heating do?

Thanks again for all the help.

 

[racerone]

???-----There should be an overheat horn in the control box.---You need to test it to see if it works.

 

[RaisedByWolves]

What kind of damage?

Well, I melted the plastic connectors on an Evenrude 200 trying to back a houseboat off of the beach. The motor was ingesting the exhaust and this marina we rented from had unplugged the warning system due to frequent complaints and "Help" calls from normally operating boats with novice renters.

I thought I was good until it shut down.

That was an extreme example, but with a motor that size taking it to the water and testing there is the way to go.

You dont even need to leave the dock knowing what you know. Just re do the test you did with the muffs and see if it gets as hot.

If it doesn't get too hot take it for a ride and check periodically for temp.

My dads 72 merc 115 put out hot water. not scalding hot but pretty hot.

 

[oldboat1]

I pretty seriously overheated an early 70s 85, and managed to get away with it -- smelled it at about the same time I noticed the overheat lamp lit up on the control box. So it isn't necessarily a disaster when it happens. (I was running fairly slow in some chop -- probably would have been worse if I had been going balls to the wall while the motor was burning back there.)

I got spooked and put in a temp gauge after that, but just being a little more thoughtful about water pump maintenance would have been enough. Good to make sure the warning system works, like suggested. Adding a tell tale would tell you at start up that the pump is working, but won't help you much when underway unless you drive looking astern.

 

[Markoku]

???-----There should be an overheat horn in the control box.---You need to test it to see if it works.

How would I go about testing the over heat horn? Is that something I can do in my driveway? If I can confirm that the over heating horn works. Then I should be able to launch the boat, get it up to temp. And if I don?t get a warning I should be good to go.

Just in time for winter...

 

[F_R]

How would I go about testing the over heat horn? Is that something I can do in my driveway? If I can confirm that the over heating horn works. Then I should be able to launch the boat, get it up to temp. And if I don’t get a warning I should be good to go.

Just in time for winter...

The horn sender switch is in one of the cylinder heads, with a tan wire going to it. To test the horn, bare the wire and short it to the head (key switch on). The horn should screech loudly. BUT, that only tests the horn and electric circuit--it does not test the switch.

By my experience, my trust in those horns is zero to none. I've seen way too many of them that either sounded off AFTER the motor was burnt up, or not at all. Your mileage may differ.

 

[Markoku]

The horn sender switch is in one of the cylinder heads, with a tan wire going to it. To test the horn, bare the wire and short it to the head (key switch on). The horn should screech loudly. BUT, that only tests the horn and electric circuit--it does not test the switch.

By my experience, my trust in those horns is zero to none. I've seen way too many of them that either sounded off AFTER the motor was burnt up, or not at all. Your mileage may differ.

Ok, so it sound like the only real way to test this is to let the boat idle in the water until it comes to temp, 5-10 minutes. Then I should see if it starts spitting a little more water then when it?s cold. It sounds like if the motor is going to overheat while I?m underway, I?ll find out once it?s to late.

 

[F_R]

You can add a tell-tale if it bothers you that much. There is a hole already there for it, left over from bygone days. Simply drill it through till you hit air, then STOP. Run in 1/8" pipe thread tap, then screw in a hose nipple and a pee hose. Restrict the flow somewhat, because it will bleed off way too much if you let it free-flow.

 

[F_R]

No Title

 

[Markoku]

You can add a tell-tale if it bothers you that much. There is a hole already there for it, left over from bygone days. Simply drill it through till you hit air, then STOP. Run in 1/8" pipe thread tap, then screw in a hose nipple and a pee hose. Restrict the flow somewhat, because it will bleed off way too much if you let it free-flow.

Thanks! I might give it a try. Its not that it bothers me, its that I don't know much about boat motors, and don't have the money to replace this one if I seize it. I'd let it idea at the dock for a while and see if its overheats.

 

[oldboat1]

Get an IR gun and go for a run with it -- cover off, friend driving. Let it warm up at the dock and check the head temps (top of the heads). Run it for 10 minutes or so at maybe half throttle; idle back down, and check temps again. Repeat until satisfied the running temps are normal (140F or so). If it's hitting 160, it's running hot. Hang reasonably close to the launch site until comfortable....

A tell tale might be good, like F_R suggests. You might also consider a temp gauge, or a gauge along with a tell tale. A tell tale will tell you if the water pump is working (provided the little outlet isn't clogged), but hard to see underway unless you drive looking astern(!) A temp gauge tells you what the temp is at any given time (surface temp of the head where the sender is attached).

Need to just have some fun with it, though, whatever you do -- be able to trust maintenance.