Well, since Beer-30 asked in another thread I thought I would start a thread on my project. For some reason I lost a ton of power and compression over this last season so I decided to take it out and tear it down. The motor is a 502 Mag EFI. I am not the most knowledgable on this but I have a buddy that is and he is helping me do it. I was surprised when I found out it was a Gen VI and not a V! Based on the year of the boat and the Mercruiser Serial #, everything pointed to a Gen V and I was going to convert it to a Gen VI. Anyway, here goes.....
How many have pulled your motor with one of these?
http://www.lasvegas***boats.com/iB_h...-IMG_1808a.jpg
I was expecting to see either a burnt valve or some bad springs but didn't find either.
http://www.lasvegas***boats.com/iB_h...-IMG_1824a.jpg
Well, maybe a some cracked pistons or bad rings???? Doesn't look like it.
http://www.lasvegas***boats.com/iB_h...-IMG_1825a.jpg
About this time we were scratching our heads trying to figure out what the problem was. It wasn't until we turned over the block to take the pan off that we found our problem.....I wonder if this is it???
http://www.lasvegas***boats.com/iB_h...-IMG_1826a.jpg
It seems that when they assembled this motor somehow an extra rod nut was left in the pan. It just took 10 years and the perfect wake at the right time to send this nut up into the cam. It must have gotten stuck in there for a time or something. It tore up a lobe pretty good and busted another lifter, too. Oh well....time for more HP!!!!
I purchased an upgrade kit from Crockett marine engines which should bump the HP up to around 510-520. Block and heads will be going into the shop next week for all the machine work and I should be putting it back together at the end of this month. More to follow.