1995 Johnson Outboard steady long alarm goes off when going at slow speeds like through a no wake zone?

Question

Mostly seems to be happening after refueling at Marina. If I go full speed and then shut off for about a minute it seems to go away. Also happens when idling for a couple of minutes like picking up crab pots. Have tried pumping the oil bulb and gas bulb but seems to not be the problem.

Answer 1

I am guessing it has no sensors you can monitor? It may be over heating and at speed the fan is up. Have you checked to make sure nothing it caught in the prop? I don't know since my jet boat doesn't have alarms it just lights up a dash icon.

Consult your owners manual.

Answer 2

That's the over heat alarm> thermostat's might be bad> Have had a bad sensor in the heads> if pumping water OK> Disconnect 1 side at a time to see if it's a sensor> Before doing anything major>Does the engine feel hot to the touch or just warm??

Answer 3

That is your overtemp alarm.  *STOP* running that engine until you figure out what's wrong.  You can turn a repairable engine into an anchor pretty quick like that.

When you say "does not feel hot", what are you feeling?

If you think your temp switch might be malfunctioning, you can test it in a pot of water with a kitchen thermometer using a multimeter or test light & 12V power source.  It should close at 163ºF.  The temp switch is high on the cylinder head at the end of a tan wire.  If it's a V4 or V6, there's one on each cylinder head.

Change the water pump impeller & were it mine I'd go ahead & do the termostat(s) now too.  

Running in salt water you should change the impeller annually and inspect and/or replace the thermostats at least every couple years.  

There's also one or more bypass valves (depending on which motor you have), under the cylinder head cover(s) that suffer from corrosion in salt water use.

Do you flush with fresh water after every use?

Overheating can also be caused by bad timing, and by lean mixture.

Any other symptoms at all?

Done any recent maintenance to the motor?

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[edited] you've got way more salt experience than I do;  heck I change impellers every 3 years or so freshwater only.  They most always look pretty good, unless I've run up on a sand bar or something.  That's the one thing I replace before it wears out.

General rule, if you can hold your fingers against the cylinder head for more than a few seconds without permanent damage, it's not too hot.