Blown head gasket?

[ttherou]

I have a 87 merc 115 hp I6 which has a water leaking from the starboard side, top part of motor near the head. I cannot see where it is coming from due to accessory brackets that are in the way. The last time that I ran the motor I lost a singificant amount of power while at WOT and my speed dropped 10 MPH immediately. I am thinking that I blew the head gasket. Any other scenarios? How hard is it to replace? Also, would I need to remove the engine from the lower unit? Any guidance would be appreciated. What is that saying about a boat owners two happiest days?

 

[Capt Ken]

Re: Blown head gasket?

That engine has no head thus no head gasket. If you have water leaking its possibly from the water jacket. Thats what the bolts are you see around the sparkplugs you are thinking are head bolts. Check your compression, those inline sixs are bad to fry cylinders.

 

[AMD Rules]

Re: Blown head gasket?

A leaking water jacket cover is often a result of overheating. I wouldn't recommend running that motor again until you confirm that the water cooling system is in good order(check the impeller), and that the fuel (lubrication) system is functioning well. Check for cracked or decayed fuel lines which may have caused a lean running motor. Good time to clean the carbs.

A compression test, and a visual inspection of the pistons/cylinders through the intake covers would be a wise move at this point.

Ideally, you want to see compression within 5% of each other, and above 100 psi.

The leaking water jacket is relatively easy to fix, provided you can find out what caused it to leak.

 

[Texasmark]

Re: Blown head gasket?

I had the same engine and after several years had the same problem. It's the seal on the water jacket and corossion of the mating surfaces to the block flake off and cause the leaking.

Like Capt said, Merc had no head in those days; the block was cast as integral cylinders and head. It can be purchased from the NAPA auto parts store's Marine catalog for about $10 if you have no dealer handy. Be sure and clean up the engine/cover good before you replace it and you might use some gasket spray to help in sealing the alum against further corrosion. I like to use "Kopper Koat" head gasket sealer spray on my gaskets.....regardless of whether or not they say to install them dry.

Mark