I have twin 540 cube engines with B&M 8-71 blowers, after the boat sit's for a week it's hell to start and when it does it's not running on all cylinders, after 2-3 minutes of warming up all cylinders are fireing and runs good, now i'm running NGK V-9's Maybe too cold??? I bought a nother set and the PPart number is different except for the -9 and the threaded shafr section is longer.