I am guessing that if I use a laser on the intake manifold right at the temp sender location or a few points along the intake that the temp will read lower than the actual water temp inside/flowing thru the manifold. Has anyone compared laser gun temp vs a known good dash gauge temp? Trying to determine if dash gauge is a few (maybe 10) off? Perhaps sender, regardless I am reasonably certain the measured surface temp will be lower than the water inside. Just wondering if anyone has determined if there is any repeatability to this method vs actual.

Next step is to pull T-stat and heat in a pan of water with an old school candy thermometer or such. Chasing an issue on 5.0 MPI. It idles at a solid 180 on gauge, runs at 180 and a needle width or two above 180 at 3200 to 3600 ish range, looks like it might be 185. It looks like a standard 160 T-stat was installed a while back but it was likely a china crap piece. Considering replacing it with a high flow SW brass T-stat with a few holes drilled. I know the cooling system should be capable of cooling a 305 to whatever temp. Bravo belt driven seawater pump, new impeller but old risers and manifold. Riser temp is fine, one side just a bit higher than the other so I am not suspecting clogged manifold or risers.

This setup has the spring loaded plastic balls (on t-stat housing assy) that go to the risers. Has anyone had any luck trying to balance these by stretching one spring a bit? Idle temp on one riser is noticeably hotter but not HOT, running at 3k they even out some but one is still a little warmer. Might just try to pinch hose down on one to force a little more water to the other side. Just trying to do a few simple things before pulling circ pump, replacing risers etc.

This is on my sons boat that I just replaced the intake manifold on for a casting flaw that rusted thru and made water injection on cyl 1 an unwanted option. It ran at 180 (indicated) last year. I would rather see it in the 160 range. I am hoping it is just a crap china t-stat.

I usually see about 10 degrees or so cooler on surface temp w infrared vs a probe in water fwiw

Beware IR thermometers are not very accurate unless you adjust for Emissivity, I'm not at 10 posts so cant post a link but search for something like "emissivity table fluke"

Now have enough posts to be allowed to post a link :-)
https://www.flukeprocessinstruments....ssivity-metals

Ayuh,..... Don't do that,..... Risers rarely to never run the same temps, especially at idle,.....

​​​​​​​There's No problem,..... leave it alone,....