Are you using one of those infra-red non-contact heat guns?

If so, just ignore that reading -- the numbers they return are affected by so many factors that they're only useful for making relative readings rather than absolute ones (ie: if your engine is running hotter or colder than it was yesterday).

If your engine is cowled it could be that you've got insufficient exit area for the cooling air. The rule of thumb states that the hole(s) where the air comes out of the cowl should be at least twice (and preferably three-times) the area of the hole where the cold air comes in.

Can you post a picture of your setup?