High Temperature Alarm

Looking to prevent a future problem...
Recently blew up my Merc, and before I install whatever new powerhead or engine, I would like to install a High Temperature Alarm and a water pressure gauge.
My question is, where do I begin to look for a Hi-temp alarm Kit, that I can wire in? And where would be the best place to locate the sensor ,say in an inline 6, Top cylinder, or Middle cylinder, Or bottom?
Thanks.

Re: High Temperature Alarm

More info about the model & HP of your motor would be helpful.

Re: High Temperature Alarm

The engine normally already has an alarm but not knowing what year and HP it may not. Water pressure gauges come with instructions for installation. If you install a new power head, then by all means install a new water pump BEFORE running the engine. If you don't know WHY the engine went bad, it would be a good idea to rebuild the carb(s) as well since lean fuel mixtures generally destroy more motors than anything else. Unless you determine what went wrong, not doing these things may result in destruction of a brand new power head.

Re: High Temperature Alarm

The factory sender was part #87-96829A1(wrote it on wall behind workbench) and this tie's into existing wiring that we spoke of,and the water pressure gauge need not to exceed 15psi.

Re: High Temperature Alarm

Thanks , I have heard in my limited exposure to all of this a couple of different times about a lean engine running itself to destruction, but I have a couple of questions regarding that, if I may?
1-I have been running this engine flat out several times before and for a great deal longer than the minute or so it ran this last time when it blew...can an engine go lean "overnight"? AND...
2-I have pulled the plugs a couple of times before this happened and they looked like they were running with just the right amount of fuel. Even after it scorched itself, all the plugs came out ever so slightly wet and clean, except for the number one plug, which had a fresh coating of aluminum piston dust on it. Is it possible to determine the actual cause of this meltdown from any other clues when I tear down the block?

As soon as I decide what powerhead or engine goes hung on the back, I will look into the ideas and suggestions regarding the temp alarm and whatever engine I decide to go with is definitely getting the complete once over, including any repairs, replacements, or adjustments necessary to try and prevent any future catastrophies like this one from occuring...

Also changing my signature to contain all necessary boat/motor info...

Regards, Gus

Re: High Temperature Alarm

Yes you may be able to determine what caused the meltdown.In a Tower there should be a oil feed line from the bottom of the head to the top cylinder that routes under the flywheel.That would be the first thing to check,may be cracked near the top.Sucking air will negate any oil from lubing that cylinder.Due to the nature of the tower that line picks up excess oil from the bottom and feeds it up top. Just tore one down and that is what I found with #1 meltdown.That would be one of the top things to look for.

Re: High Temperature Alarm

Yes -- an engine can go lean overnight, next week, or in five minutes. A bit of debris entering the skinny carb passages is all it takes. Once that happens, the meltdown can occur in minutes especially at WOT. A properly running engine will display plugs with a very light to medium tan color after a long WOT run and then quickly shut down. Checking plugs after a prolonged periiod of idling is not a valid check.

Temperature alarms use a temperature "switch" that closes at a specific temperature, thus sounding an audible alarm and in some cases, turning on an idiot light on the console or in one of the instruments. Temperature "gauges" require a temperature "sender" that is a resistor which varies in relation to engine temperature. It is good policy to have both. Once an over-temp alarm goes off, the damage may already be done.

Re: High Temperature Alarm

Towers will damage themselves from lean running as was cited, lack of cooling water, overadvanced timing, over propped, or a combination of all of these.

Normally # 3 cylinder will fail first, followed by #1. Just a data point, nothing else. I would therefore recommend a waterpump rebuild, fuel pump rebuild, all carbs cleaned, and link and synch. Definately install the water pressure gauge and keep an eye on it while running.

Re: High Temperature Alarm

Silvertip said:

Yes -- an engine can go lean overnight, next week, or in five minutes. A bit of debris entering the skinny carb passages is all it takes. Once that happens, the meltdown can occur in minutes especially at WOT. A properly running engine will display plugs with a very light to medium tan color after a long WOT run and then quickly shut down. Checking plugs after a prolonged periiod of idling is not a valid check.

Temperature alarms use a temperature "switch" that closes at a specific temperature, thus sounding an audible alarm and in some cases, turning on an idiot light on the console or in one of the instruments. Temperature "gauges" require a temperature "sender" that is a resistor which varies in relation to engine temperature. It is good policy to have both. Once an over-temp alarm goes off, the damage may already be done.

Click to expand...

OK, so now you have properly scared the you know what out'a me...besides religous maintenance, is there any way to prevent a lean melt down? Other than, of course, not running at WOT? Is it possible that this could also occur at part throttle settings for extended periods of time?

I want to get some clarification on a hi-temp alarm...

I have found a couple of sources that offer electronic units that are adjustable to within a couple of degrees above normal operating temp of a particular engine... my understanding of mechanics is that "meltdowns" occur when an engine goes way above its normal operating temp...


These 'new-fangled' electronic alarms are supposedly accurate enough, that they give a constant actual, accurate reading of the engine's temperature, and can be set to go off well before any overheating damage is done...again supposedly, because I have no experience with them...


If this is correct, and anyone has any knowledge of these, please, feel free to chime in...


Running lean, too much timing, overpropping and overheating would tend to exhibit the same types of overheating effects and therefore, based on my limited understanding, could possibly be prevented by the use of such an alarm...

TRUE or FALSE?


Any and all pertinent comments welcome.


Seems the deeper I go, the deeper it gets...:facepalm:
Thanks, GT

Re: High Temperature Alarm

Yes -- an engine can fail at part throttle settings. As for timing, cooling, prop selection -- all of those are contributing factors to engine failure as pointed out. Eliminate them as soiurces of failure by having the engine properly tuned and serviced (by someone that knows what they are doing). Remember this -- unlike a car, your boat does not have a multi-speed transmission. It has one gear that must get you started, on-plane, cruise, and run wide open without over-reving and at the other extreme, without lugging. Theredfore prop selection is critical to overall engine performance. One size does not fit all in this regard. The right prop is one that allows the engine to operate at or very near the upper end of the manufacturers recommended WOT rpm band with what YOU consider an average load.

Lastly - setting a temp alarm at any point below what the manufacturer says is an overheat condition would likely mean the alarm goes off when the engine is not really overheating and you therefore begin looking for problems that don't exist. That said, any alarm is better than no alarm.

Re: High Temperature Alarm

As noted when a carb goes lean, for whatever reason,you will not be lubricating that cylinder/cylinders and a"meltdown" will occur.So the temp gauge may still be within limits and you will take out a cylinder before the gauge has time to react.It takes seconds for a motor running at high RPMs to grenade with no lube.If it is a water issue you can watch the temp gauge climb or have it set so that it shuts down,not so with a lean condition,it happens to fast in MOST cases.ALL motors can go at anytime do to poor casting,bearings,belts going etc,something you live with.No gauge is going to warn you that a main crank bearing or rod is about to let go.

GT1000000 said:

OK, so now you have properly scared the you know what out'a me...besides religous maintenance, is there any way to prevent a lean melt down? Other than, of course, not running at WOT? Is it possible that this could also occur at part throttle settings for extended periods of time?

I want to get some clarification on a hi-temp alarm...

I have found a couple of sources that offer electronic units that are adjustable to within a couple of degrees above normal operating temp of a particular engine... my understanding of mechanics is that "meltdowns" occur when an engine goes way above its normal operating temp...


If this is correct, and anyone has any knowledge of these, please, feel free to chime in...


Running lean, too much timing, overpropping and overheating would tend to exhibit the same types of overheating effects and therefore, based on my limited understanding, could possibly be prevented by the use of such an alarm...

TRUE or FALSE?


Any and all pertinent comments welcome.


Seems the deeper I go, the deeper it gets...:facepalm:
Thanks, GT

Click to expand...

Re: High Temperature Alarm

It is not as dire as it appears. Verify proper timing of the ign, and prop her correctly as was recommended. Keep up on the waterpump maintenance, and use fresh clean fuel, and you may never experience a lean meltdown.

Re: High Temperature Alarm

Well, let me start out by saying that I have changed my shorts and want to thank you all for the excellent information.
I am going to do my due diligence, as I had done before and then some, to take every possible precaution and hopefully prevent any future meltdowns...
Now, for the rest of the story...
I have been tearing into the power head in the hopes of both finding out what it would take to repair it and WTF went wrong...
I found what caused my meltdown and do not think there is any way I could have prevented it...
Let me 'splain...
When I finally removed the power head from the exhaust extension, I was just looking and learning as I went along, and...
EUREKA!!!

There, where the water inlet tube that comes from the water pump to the engine, was a piece of an impeller blade about 3/8 of an inch wide and complete from top to bottom, that apparently acted like a flapper valve and cut off the flow of water to the engine...
I can definitely say that it was not from any of the 3 impellers I had previously changed, since all of the ones I replaced, were either melted or in good condition. Even the one that came out of the engine after it was fried, was still 99% all there.
This was something I would have never thought to look for and was probably floating around in there since before I got this boat.
Unfortunately, it picked that day to rear its ugly head, but would have probably occured at any time in the future, as it was too big to get past the spot it got stuck in...
OH well, as they say, say la vee, or whatever...
I took a couple of pics of the spot with the chunk of impeller in it, but I couldn't get enough light in there to see it properly.
In the first two pics, you see the water inlet opening where I found the piece of impeller, and the next two show the chunk of impeller...
Other than removing the water inlet tube during any one of the water pump replacements previously, I do not know of any way, this could have been prevented...I guess that it might be something to keep int mind, when servicing a previously owned motor, that you don't know the history of...
For me anyway, it is a hard, expensive lesson learned...
Regards,
GT

Re: High Temperature Alarm

Water pressure gauge probably would've saved you. Definitely going to put one on my 83 after seeing your troubles, thanks for your sacrifice to open my eyes