posted 07-13-2015 04:11 PM ET (US)        

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Last 500 yards to dock in shallow water, telltale [on what is later identified as a 2006 production year Mercury 90-HP FOURSTROKE outboard engine] goes dry. We carefully idled it back on trailer. Back home, ran on hose adaptor ear muffs, a few short tries, nothing but a few telltale drops at a time. I then [used nylon] weed-wacker string [to perform some] thing [unexplained], but that did not much change the stream. Using back-flow through the telltale hose connection did [cause a change], and [the volume of water flowing through the tell tale outlet] eventually returned to a normal stream.

After shutting down motor and water flow, the telltale kept tricking down for a bit of time, two minute, perhaps. I do not remember it doing it before, or, maybe I never paid it any attention. Could that be a sign that there is still an internal minor obstruction like sand or weeds? How far into overheating would you go before alert would come on? Only aural alert I know is the one you get when you trip the safety switch via lanyard.

posted 07-16-2015 08:01 PM ET (US)            

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Thanks, tedious. The telltale trickles a little bit for two minutes AFTER muffs have been taken off, looking like (a portion of) the engine block coolant is emptying out, I think.

I have prior owner's four years of shop work records, and, as I recall, water pump was looked at recently, not sure about thermostat.

I will run on muffs again, for longer this time, hoping that thermostat cycles, and observe.

posted 07-17-2015 08:40 AM ET (US)            

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Jay, both water pump and thermostat are regular maintenance items. Since you are new to the motor, if you don't know that they've been changed fairly recently, you might want to get it done, both to be on the safe side and so you won't have to worry about it for a while.

Tim

posted 07-17-2015 09:23 AM ET (US)            

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quote:

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After shutting down motor and water flow, the telltale kept tricking down for a bit of time, two minute, perhaps. I do not remember it doing it before, or, maybe I never paid it any attention. Could that be a sign that there is still an internal minor obstruction like sand or weeds?

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The confidence stream nozzle or overboard indicator or telltale stream outlet can be located in difference places in the cooling system of outboard engines, so there is no particular way to know what the behavior ought to be for an outboard engine in regard to how long cooling water will flow from the confidence stream nozzle or overboard indicator or telltale stream after the engine has been shut off without studying that particular engine's cooling system.

posted 07-17-2015 09:26 AM ET (US)            

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How far into overheating would you go before alert would come on?

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I don't understand what is being measured by "far"? Do you mean far in terms of distance? Do you mean far in terms of temperature? Or, far in terms of time?

The sensor that operates an alarm indicator does not know much about distance, or time. It only knows about temperature. It does not changes its behavior based on any operator input. Whenever the temperature of the sensor exceeds the alarm threshold temperature, the sensor indicates an alarm. This does not vary according to any other parameters or according to what the operator is doing.

posted 07-18-2015 12:33 PM ET (US)            

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Thanks Jim, "far" was meant as temperature threshold.

Operator manual has nothing specific on this, and shop manual explains how to fix things, not witness problems...

I also have a Mercury service shop a few miles away, I could stop and ask.

Other: I opened the motor to see what I could figure with the telltale routing: not much, goes down into the lower unit.
I did discover that I could possibly rotate my telltale port so as to make it shoot slightly to the side, instead of in-line with motor - easier to see at a glance.
I also noticed the pull start sting and puller...!

posted 07-18-2015 01:50 PM ET (US)            

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Thanks for the clarification that by "far into overheating" you mean how much temperature rise would be necessary to cause the aural alert to sound. As I mentioned, the sensor is very likely to be set to a fixed temperature, and when the sensor reaches that temperature the aural alert should sound. I don't think the operator can influence that.

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Operator manual has nothing specific on this...

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I am not familiar with the operator's guide for a 2006 Mercury 90-HP FOURSTROKE. I found this one available on-line, dated c.2001. Perhaps it covers your engine:

http://download.brunswick-marine.com/filereader/file/pdf/4/enen/ outboard/2001/4-stroke/10215z10.pdf

It seems to confirm what I suggested: the aural alert comes on when the sensor detects overheat. That seems rather specific.

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...shop manual explains how to fix things, not witness problems.

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Usually a shop manual will have a diagram of the cooling system and indicate the path of the water flow. You will have to analyze the cooling system with an eye for where the overboard indicator is tapped into the cooling water flow in order to develop a concept of how much water might flow out of the engine block when the engine has stopped and by what path. This should help you determine if the amount of water you see flowing out of the overboard indicator after shutting down the engine can be interpreted as a sign of a malfunction of the cooling system.