Engine is a Merc. 5.0L/230 (1985). Starts fine when cold. If I run it even for as little as two minutes and try to restart, it will turn over slowly as if it were fifty below zero. It turns over maby two times. Battery was new last fall and stored inside. Battery reads 12.75 on vlt. meter after shutoff, 12.5 after trying to restart one time. Temp. gauge was barely above 100. Any help appreciated.