I have a 1996 Mariner 50hp 4 stroke motor and it the alarm comes on
sometimes. The oil is fine. I had the water pump replaced. It doesn’t
do it all the time I go out.

The other day we were just putting along about 6-10 mph for about 20
minutes then I stopped to talk to someone and put it in neutral and
about a minute later the alarm went off. I shut it off and started it
up and it was fine. Stopped at an island for a few hours and on the
return trip back it did it again. Shut it down and waited a minute
then it was fine.

Another time we were going fast (for a pontoon boat) about 15 mph
pulled over at another island. Only stayed for a few minutes the left
then the alarm comes on. Shut it down then it was ok for the rest of
the day.

It happened other times also but these are the most recent. Water
temps are in the upper 80’s.

Any ideas? I was thinking of getting a temperature gauge but I’m not
sure what kind to get and how to hook it up.