Motor Meltdown What could have caused it?

Question

have a major issue!

Purchased a 1982 26' carver with a 260 mercruiser engine.

The engine block was replaced 2 years ago, apparently a cracked block.

Previous owner claimed he drove the boat for 8 hours after the block was replaced with no issue.

My first lauch this occurred.

Boat launched outdrive lowered.

Engine started (quite easily)

I revved to about 2000 rpm

within approximately 5 minutes I smelt an odor

Opened the engine cover and nearly ****!

Looked like smoke coming out of the air breather.

I left it idle removed air breather and steam was coming out of

both hoses which go from rocker cover to carb. Much steam.

The starboard exhaust port melted the elbow and popped two of the 4

S.S strap clamps. The exhaust elbow severely deformed.

On the same side (Starboard) a milky substance (oil & water) was coming

out somewhere underneath the exhaust manifold.

The boat ran for about 8 minutes and when I shut it off it made some very

rude sounds while cooling. The sound of metal contracting from being heated.

I checked the dip stick and water was evident in the oil.

Any ideas as to what may have happened? Impeller not functioning/ thermostat shut closed/ blown headgasket?

I am looking for adivice on what to look for and where to start on repair.

The boat sat in outside storage for approximately 2 years.

I did test run with outdrive muffs on but really only to ensure it turned over and started, maybe 5-6 seconds.

Thanks for any advice you may have.

Answer 1

My first thought would be that the motor was never put together correctly, my 2nd thought would be a blown head gasket, my 3rd would be improper cooling. I would honesty start with the first option.  

Answer 2

Pretty obvious overheat condition probably caused by waterpump failure.  First start-up, you should always watch the gauges carefully.  When you ran it on the muffs you should have looked for good water flow from the prop hub.  Take it to a rebuilder for diagnosis, but it is probably toast.

Answer 3

Sounds like a blown head casket.could have been caused by by the rebuild- Should have went for a 30 minute checkout spin before any money changed hands.

Answer 4

FIRST AND FOREMOST: STAY AWAY FROM THE LINK THAT baqpahs h PROVIDED IN THEIR ANSWER! NOT WHAT YOU OR ANYONE WANTS AND HAS BEEN REPORTED.

Now, not being a mechanic my 1st thought would have been that your impeller wasn't working and that by leaving the engine running as long as you did you may have caused more damage to the engine that could, note "could," require replacing the engine(s).

Water in the oil is never a good sign and while you did a great job of letting everyone know what happened you didn't say where your located and if the engine could have frozen during the 2 year stretch. Was the vessel winterized each of the 2 years she sat out of the water?

Where to start on repairs? Do not attempt this from the beginning by yourself. Get a certified Merc mechanic involved to tell you what you need. My druthers say to have this repaired professionally unless you are extremely comfortable with working on the engine(s).

Sorry to close with this but you should have done an in water test run with the vessel instead of just using the muffs. The reason for this is you would have discovered at that time that there was an issue that would not have cost you hard earned money now and you could have walked away from it.

Always hate hearing about things like this happen and wish you nothing but the best of luck in getting her repaired.

Answer 5

head gasket or cracked block. Sometimes when the original block went they didnt replace it just repaired it insufficiently..cheap fix lasted long enough for you to get hooked.  

Answer 6

Did you remove the muff before launching it> The damage you have said is extreme so the engine will have to be torn down> the outdrive will have to have a water pump checked> Since it overheated to melt the exhaust> Might want to look for a complete engine>As there might have been issue before you brought it?