525 heads leaking coolant into bilge
 

Hello All,
I have a slight coolant drip from the bottom of each cylinder head, on both sides of the motor. I noticed this late last season, and closely monitored it on the last few trips.
Motor is a 2005 Merc 525. 450 hours. CMI headers are new. I was told that head work was performed at some point, by previous owner. Has ARP head studs, which I believe this early gen 525 may have came with GM studs.
No coolant leaking into heat exchange. No coolant leaking into motor, and no signs of coolant in oil. No oil leaking into coolant system.
Boat runs great. Just has an ounce or two of coolant in the bilge after running all day.

I've searched the forum and haven't been able to find any info addressing this particular issue

Best case, Could this be an issue of the heads never being re-torqued after install? Could a re-torque resolve this?
Worse case, I would assume warped heads?

Before heading to a local boat shop, I just wanted to ask around to determine if anyone had any experience with this issue?

are you sure its not coming from the heat ex-changer where it bolts to the head ? there is an 0-ring seal there

If I remember correctly; After a day of running, there is a small amount of visible coolant that remains on the block, under the cylinder head. Very minimal, About 2-3 small droplets.
I read somewhere, that the coolant passages are very close to the edge of the cylinder head and if the heads are not torqued down properly, coolant can seep out (external leak only). But of course I can not find that thread now.

LIke F-2 Speedy suggested, there is a high probability its the o-rings for the heat exchanger.

May want to pull the exchangers and replace the O-rings. When service these engines I typically put a small amount of Right Stuff on the o-rings to make sure it seals.

Panther VoodooRob
Thanks for your input !
Are you referring to part #18 in the schematic?
I replaced the heat exchanger end cap gasket (17) and the o-ring (18) during the last service. There is not leakage from the heat exchanger caps.
If you are recommending that item 28 o-ring is leaking, this would not explain the visibly coolant on both sides, port and starboard.
https://cimg3.ibsrv.net/gimg/www.off...69041a9e66.gif

28 oring is on each head so each side

pressure check and should be a easy find . i thing a gm thread adapter should work

My ex Baja 525's had same kind of leak after full engine rebuild. Block deck surface was a little bit too raw finish for multi layer head gaskets. Engines had originally conventional gaskets but I replace them with better ones. You can try small amount radiator fix additive to coolant. If it leak from small grind scratch it should help.

Go to your local auto parts store and buy a bottle of leak detecting die and a cheap UV flashlight if you don't already have one. Put the die in the cooling system and after a run get the flashlight out. The die glows bright green with the UV light and you should be able to see where it is coming from. Its amazing how far fluid will travel from the actual leak point.