Section 65. The chief engineer and assistant engineers shall be chosen for terms not exceeding three years; provided, however, that the district, at any meeting held in accordance with section 66, may vote to authorize the prudential committee to appoint the chief engineer and assistant engineers on merit for an indefinite period of time. A chief engineer or assistant engineer may be removed for cause at any time after a hearing by such prudential committee. Fire districts may accept the provisions of section 42.