Ed brings up a bunch of great ideas to check, more or less in order of probability.
I don't know a lot about engines, but I do cook a lot and have over/undercooked my share of meals......
How do you know that the reading on your "Candy thermometer" is accurate?
Some are adjustable, but many, many are not and five different ones bought at "Bed, Bath & Beyond" will probably give five different readings (even the electronic ones).
Calibrate it with a cup of boiling water to see if it reads 212º.
Some of them have a locknut at the underside of the pointer housing - loosen that, rotate the housing to show 212º and re-tighten. If it's not adjustable, consider getting one that is.
Also, I've found, to my chagrin, that using a laser-pointer thermometer can really be ambiguous because of the reflectivity of the surface being probed. For example, I used mine (an expensive Fluke) on the ducts of my gas heater and found that the difference in indicated temp between a painted steel housing and the raw aluminum duct 2" downstream was about 20ºF !!
Temperature robustum cave