Water leaking from around spark plugs

[alrednek]

I have a 1976 Mercury 85 hp outboard that has water leaking from around one of the spark plugs. I looked through past posts and suspect that it may be a gasket problem...I sure hope so anyway. I'd like to get some opinions about whether this is the likely problem and about just how involved it would be to repair. I am fairly good with making mechanical repairs if someone can lead me in the right direction. I have rebuilt the carbs, replaced the water pump impeller, and replaced the shift/throttle cables on this engine. Would this repair be similar in difficulty level? I have a Clymer shop manual that covers this engine, but doesn't give any troubleshooting information on this specific type problem. Thanks for any help/advice you can give.<br /><br />Mike Hannah

 

[Walker]

Re: Water leaking from around spark plugs

Yes, it will be the water jacket gasket. That motor doesn't have heads so the only gasket that can leak is the water jacket gasket. IMHO it is a sorry design with no bolts around the center.

 

[Troy_from _Oz]

Re: Water leaking from around spark plugs

Mike Hannah, <br /><br />I recently had the same problem with my 72 Merc650. I think these engines are somewhat similar. Advice from the board was that it was the water cover gasket, which I couldnt source here in Australia. I left it one more boat outing and it got heaps worse. It turned out to be corrosion of the cylinder top where the spark plug screws in. I believe this was a legacy of the last owner not replacing the impeller regularly. When I replaced it, the increased water pressure cleaned out the corrosion. the best way to fix this would be to strip it all down and have it welded then machined flat again. Unfortunately marine mechanics wont touch my engine around here (due to its age and fear of creating more problems when disassembling). I ended up finding some high temp metal putty to plug the hole. it seems to be holding - for now. I guess the moral of the story in my case was that what appeared to be a simple leak turned out to be an indicator for a more serious problem. I guess i can now pretty much guess the condition of the rest of my motor with regards to corrosion now.<br /><br />Best of luck<br />T

 

[alrednek]

Re: Water leaking from around spark plugs

Would the gasket I need be identified as a *water jacket cover gasket*? I found that gasket listed on a Mercury parts page as part# 27-73665. Just checking to see if anyone can confirm that as the correct part #.<br /><br />Thanks, Mike Hannah

 

[Troy_from _Oz]

Re: Water leaking from around spark plugs

mike, <br /><br />it looks like the right number. I checked http://www.mercruiserparts.com/ and most of the models listed had that part number. (follow the end caps, manifold and exhaust cover link). Maybe just double check using your serial number, but it looks like the one.<br /><br />cheers - T

 

[alrednek]

Re: Water leaking from around spark plugs

OK Troy...thanks for the help. I plan to replace the gasket as soon as I can get one. Hopefully it will not be above my mechanical abilities. Good luck with your Merc.<br /><br />Mike