I have a Tower Hobbies Digital Tach and trying to tach a G-38 Engine with 18 x 10 Wooden Prop. I am getting a reading of 10,300 and that does not sound correct. The figure keep changing by large amounts. I changed the battries in the tach and tested it by aiming the tach at a light bulb. The figure on the tach was correct with the light bulb, 3,600.

If I paint a couple bands on the prop, will the tach pick up better?

thanks,

Ed