Add-On Outboard Motor Overheating Alarm?

[Texasmark]

Re: Add-On Outboard Motor Overheating Alarm?

What about your exhaust water jacket cover on the left side. Nice flat surface. Don't remember if you had a stat or not. The exhaust is a separate circuit from the block, but will tell you if the water pump is pumping. If no stat, then you should be good to go.

Course, with a couple of tubes of JB you could paste it right above and slightly to the right where you have it in the picture. Then it would monitor block temperature. On your comment about removal and all that, you are being picky again. If you want it off later chisel it off. But what difference does it make if it's on or off. Some people are just too picky to please. They want help but have all these strings attached with impossible amenities. I'm through with this thread.

Mark

 

[minuteman62-64]

Re: Add-On Outboard Motor Overheating Alarm?

What about your exhaust water jacket cover on the left side. Nice flat surface. Don't remember if you had a stat or not. The exhaust is a separate circuit from the block, but will tell you if the water pump is pumping. If no stat, then you should be good to go.

Course, with a couple of tubes of JB you could paste it right above and slightly to the right where you have it in the picture. Then it would monitor block temperature. On your comment about removal and all that, you are being picky again. If you want it off later chisel it off. But what difference does it make if it's on or off. Some people are just too picky to please. They want help but have all these strings attached with impossible amenities. I'm through with this thread.

Mark

Appreciate the input you've provided. The link to the thermostatic switch was particularly useful.

 

[minuteman62-64]

Re: Add-On Outboard Motor Overheating Alarm?

Finished some of my priority (not my priority ) home maintenance projects so back to this one. While waiting for the thermostatic switch to arrive I mounted the buzzer and tests switch on the console.

Buzzer mounted on the front of the console (see attached photo - red LED approximate middle of the inclined surface). Probably seems a strange location, but -
I already had a hole there - only had to ream out about 1/32" to make it fit;
I've already got a visual warning (my gauge) and probably won't be able to see the LED in the sunlight anyways; and, most important,
I'm hoping the sheet aluminum surface will help amplify the buzzer to make sure I can hear it over engine noise.

SPST momentary contact test switch mounted just to right of ignition switch (second photo). Thinking at that location it will become second nature to push the switch in for a test right after starting motor.

Next phase, mounting the thermostatic switch, as soon as it arrives.

 

[minuteman62-64]

Re: Add-On Outboard Motor Overheating Alarm?

Moving along, sheet aluminum console face amplifies buzzer nicely. It will take an on-water test to be sure, but, I think it will be audible over the engine and other noise.

Got my thermostatic switches in. See attached photo (penny for scale). The big one is from Senasys, and will carry 15A. I saw the little one on a post in the Johnson/Evinrude section, where a guy was doing something similar. It will carry 2A. Both have same temperature characteristics (close at 185 F and back open at 145 F). Since my buzzer only draws about 200 MA, either should work. I'll start with the little one since it is easier to mount. If it fries or otherwise gives problems I can switch to the bigger one.

Second photo shows mounting solution (top left on head). Plate is a piece of 0.063 6061 Al. Will be easy to remove to either swap out thermostatic switch or change location. I used some thermal conducting grease under the mounting plate and under the switch. Also put a SS stand-off bracket below, on the head (at bottom of photo).

Ran motor in a barrel yesterday. Head temperatures at different locations (w/HF remote gauge) were all over the map, but the temperature at the switch was always close to the higher temperatures. Again, I'll have the option of changing location of it doesn't function properly.

Next step, wire it up and try and figure out a way to do an operational test that won't fry my motor. I'm thinking of running the motor (in the barrel) at high idle while holding a heat gun and my HF temp. gauge on the switch to see if I can get it to trip.

Picky? Maybe so, but MFM.

 

[Texasmark]

Re: Add-On Outboard Motor Overheating Alarm?

Your small one should do just fine. You already know what the buzzer requires and your switch capacity is 10x of that on the small one. I like your location. If you want to, Radio Shack sells a white thermal paste which greatly improves heat transfer. Put some between the mounting plate and the engine and the sensor.

On testing, just take it off and dump it in a container of boiling water. That way you don't have to worry about over doing the test. Otherwise if you had a non contact infrared thermal sensor use that. But the water test would do fine. If you get some thermal grease you will need to remove the unit from the engine anyway so test it then....don't forget to have your key on.

Mark

 

[dingbat]

Re: Add-On Outboard Motor Overheating Alarm?

How did you come up with a trip temp for the sensor? Never been a real fan of measuring a heat soaked surface to determine what is was going on inside. Far too many external variables involved w/o doing a lot of trail and error testing first.

Surprised that you don't have a water pressure gauge or a spot for one on the motor. A pressure gauge would be more relaibe and give you a warning long before you overheated. If nothing else, use the presure gauge port and install a temp sensor in direct contact with the coolant. You would get early warning of a malfunction in the cooling system long before your head overheated

 

[minuteman62-64]

Re: Add-On Outboard Motor Overheating Alarm?

I got some of the thermal grease with the purchase of the larger unit - already applied.

I do have the HF non-contact infrared sensor that I'll be using.

The hot water immersion test will be used to check operation during annual maintenance. The initial test will be to make sure the switch is mounted at a location where it will not trip (close) under normal operating conditions or where, if it trips, will not open shortly after normal engine cooling is restored. I don't want to have to shut the engine down or wait a long time to get the switch temperature below the 145 F opening temperature.

I'm planning on running my motor in a barrel, at high idle, to get an idea if it will or will not trip under normal operation (won't be able to get up to cruising operating temp., but hopefully close). Then try and trip it by applying heat from a heat gun (carefully) and then see how long it takes to open back up.

That all said, I'll have to get it out on the water to really assess how well it works (or doesn't work).

 

[minuteman62-64]

Re: Add-On Outboard Motor Overheating Alarm?

How did you come up with a trip temp for the sensor? Never been a real fan of measuring a heat soaked surface to determine what is was going on inside. Far too many external variables involved w/o doing a lot of trail and error testing first.

Surprised that you don't have a water pressure gauge or a spot for one on the motor. A pressure gauge would be more relaibe and give you a warning long before you overheated. If nothing else, use the presure gauge port and install a temp sensor in direct contact with the coolant. You would get early warning of a malfunction in the cooling system long before your head overheated

The sensor opening and closing temp specs are: close 185 F and open 145 F, per manufacturer. My measurements were by using the HF infrared remote temp sensing device - and you're right, I don't know what was going on inside the sensor -hopefully the next round of testing will give a better idea.

My motor (1982 Mariner, 30 HP) does not have any ports or holes where a sensor could be mounted in contact with the cooling flow. I have mounted a cylinder head temp sensor and gauge, but, as noted on my opening post, when dodging aircraft carriers and Homeland Security on San Diego Bay, I can't always keep an eye on the gauge .

 

[Texasmark]

Re: Add-On Outboard Motor Overheating Alarm?

The sensor opening and closing temp specs are: close 185 F and open 145 F, per manufacturer. My measurements were by using the HF infrared remote temp sensing device - and you're right, I don't know what was going on inside the sensor -hopefully the next round of testing will give a better idea.

My motor (1982 Mariner, 30 HP) does not have any ports or holes where a sensor could be mounted in contact with the cooling flow. I have mounted a cylinder head temp sensor and gauge, but, as noted on my opening post, when dodging aircraft carriers and Homeland Security on San Diego Bay, I can't always keep an eye on the gauge .

Aluminum is one of the better thermal conductors. My OEM Merc does not have the sensor in the water. It's attached to the water jacket cover like yours. My OEM Mercury has the OT alarm set to 195 close and about 175 to open...close as I remember on opening. My TStat is stamped 143F. That is where I got the numbers I recommended to you.

On running in the barrel, you do know that if you don't add water to the barrel, exhaust gasses will heat the water. Maybe you want to do that deliberately. I have used my Harbor Freight non contact thermal gun on my engine and at the same time watched the cycling of my stat. Numbers are close enough.

Mark

 

[minuteman62-64]

Re: Add-On Outboard Motor Overheating Alarm?

Testing complete. I'm logging this one as a success.

Everything hooked up (I thought), fired up the motor running in a barrel. Got up to operating temperature (hair under 140 F by my cylinder head temp. gauge today), then put in fast idle. Got behind motor with heat gun in one hand and HF remote sensing temp. gauge in other. Applied heat gun till temperature of sensor/switch was 190 F - crap, no buzzer. Shout down and pushed my test button - nothing. Whoops, had pulled fuse while doing final hookup and forgot to reinstall.

Tried again. This time buzzer went off when sensor/switch hit about 190 F. Seems good sound from buzzer - I could hear it behind running (coverless) motor even with my 73 YO hearing.

Pulled throttle back to idle. Took about 90 seconds for temperature to drop enough for buzzer to stop (measured about 140 F on the sensor/switch). This is running in a barrel of water heated with running motor - quite a bit warmer than most of the ocean/bay temperatures I'll be running in.

That's good enough for me. As I said, I'm declaring a success.

Appreciate the input guys.

 

[Texasmark]

Re: Add-On Outboard Motor Overheating Alarm?

Glad you made it. Looks like you did it right.

Mark

 

[minuteman62-64]

Extended use report. The good news: The buzzer is easily heard when running at cruising speed. The bad news: Apparently as the Bay water temperatures increase during the summer the alarm kicks in at normal operating temperature (for my motor) and won't cut out until the motor has been shut down for about 5 minutes.

I'll check the sensor in some heated water to make sure it is still operating OK. If it's working OK I'll either try and find a cooler spot on the cylinder head or get another sensor with higher closing and opening temperatures.

The concept is good. Just needs a little more tinkering to fine tune.

 

[minuteman62-64]

Update. The old sensor worked as specified (close 185 F, open 140-149 F). Problem is Summertime San Diego Bay temps. exceed 70 F in most places and my cylinder head temp doesn't get below 145 F, even at idle.

Solution (I hope). Got another sensor from Digikey. This one closes at 203 F and opens at 158-167 F (again, these are cylinder head temps.). Done a few runs and no problem with alarm going off under normal operating conditions. I've noticed that when I have a cooling intake clog my cylinder head temp gauge pegs quickly so I'm hoping the 203 F sensor will give me a timely heads up.