Re: Lower unit?
the impeller in the lower is the most likely cause. even if it ain't the cause it needs to be inspected, replaced as to be sure of it's status, as it's routine maint. on a 1 drive every one to two years depending on who yer talkin to i reckon. if they get run dry w/o water for a min. their toast. start there. it's cheaper than a riser or manifold. you could, like hm says, be heading that way too. if it aint been replaced it's certainly suspect. both L6's i've had needed manifolds and risers, 72 and a 75. but the impeller is fist suspect always. it can be done w/o removeing the drive. i've done serveral that way. 2 person job to get it back on and fursterating though. as hm says too, lubing the drive shaft and ujoints is end of year pm too. so ya'd be gettin on to that at the same time if ya remove the drive to service it. removeing the drive is most easy too. here's the link to gettin an oem service manual. yer gonna need that.
"http://www-alt.mercurymarine.com/mnetdata/sisdata/srvcovr.pdf"
if yer in freezeing temps. don't be sure it's empty of water untill ya personaly drain it. water in it is a engine killer. 3 drain points. block, at back bottom, both i've had have been t valves, bottom of manifold, back at the bottom centered. riser, back side. all on the port side. remove main bottom of waterpump hose. the service manual has pics. ya need #1.....good luck.....
