Universal 5411 operating temps low?
I had/have the same problem....it's odd....
I say "had" because when I first got the boat a year ago (Newport 27-S MKII), the previous owner mentioned it never got hot enough, according to the temp gauge...but the engine ran just fine otherwise.....
...so I used a wire-brush tip on a Dremel tool, on the sending unit, both it's electrical connection on the outside and the lug on the end of the wire, and it's inside surfaces that contact the water..., polished all mirror-shiny, and presto, immediately got 140 degrees on my temp gauge....and that lasted about 6 months.
But a year later, it's back to not registering any more than 120 or so. I haven't taken the electrical connection apart yet to look at it, but I can't imagine it's dirty and corroded, the engine compartment is nice and dry and clean...only thing I can think of is the sending unit's fouled inside...but it actually looked pretty clean the last time I removed and cleaned it, so I'll be surprised if that's it.
The engine gets plenty warm enough....I can't stand barefoot over the exhaust manifold on the engine hatch in the cockpit for too long because it gets pretty hot (just on that edge of the hatch cover), and I'll actually get warm water out of the sink after running a couple of hours, so I know the engine's hot enough....
....maybe I just need another sending unit for this 24 year old one (I presume it's the original, but don't actually know), or the temp gauge itself?
But I'll try polishing the sending unit's inside surface again and report back.