The Truman Doctrine arose from a speech delivered by President Truman before a joint session of Congress on March 12, 1947.
Positive First. When installing a mower battery, always connect the positive cable first. The positive cable is red. It attaches to the battery terminal post marked with a plus sign, the letter P or the word POS. Attach the negative cable last. The negative cable is black.
Attach the tachometer ground wire to an engine ground of the car. This need not be directly on the battery. Much of the car frame is grounded to the battery by sturdy wires. Trace those wires to find a suitable attachment point. Attach the tachometer pickup wire.