Broke a Valve spring again....time for a new motor??

[yearzero]

Ok..so a while back I had an issue with low power, backfires, one bank not running ect... all on my 2001 4.3 Mercruiser. Thanks to the great help I got here on this forum I found a broken valve spring. With the help of Bt Doctor I managed to replace it and the boat was running great. I still had some milkshake from what I think to have been a bad exhaust manifold but with the great advice of Bondo I was hoping a few hours on the water would clear it up. It has not. If anything I seem to be loosing oil and have had to add about 3 quarts in roughly 30 or so hours on the water.

If you have time to kill and want to read 4 pages of thread its here..

http://forums.iboats.com/forum/engi...ust-put-on-new-exhaust-manifold-or-fuel-issue


I had the boat about half a dozen times on the water till last Sunday. I was towing the kids on the tube and was throttling up or down (cant remember) when suddenly there was clanking and banging coming from the back then the engine died. At first I thought I may have hit a crab trap or something but after checking the prop, making sure there was spark and fuel and countless cranks to restart the engine I gave up. While waiting for Sea Tow I pulled the valve cover off and sure enough that same valve spring had broke and I could only find one half of the keeper and the little disc that goes above/below the rocker.

So...the engine cranks over but wont start at all...not even a hint of wanting to fire up.

This week Im going to pull the heads off and take a good look around in there on both sides. Im thinking best case scenario I don't see and visible damage to the block/ cylinders and then look around locally for a new set of heads. Worst case?????

Im already thinking worse case. Since the milkshake did not seem to be clearing up, excessive oil consumption and general unknown history of the boat overall I may just go ahead and source a new long block. Funds are tight now, especially with the kids going back to school but Id rather spend more now and know I have a SOLID motor than dump money into this one only to have another gremlin pop up in a few months down the river.

When I pull the heads off later this week are there any specific signs or areas I should look at closer?

Any hope for this motor at all still or am I on the right track in thinking I should just replace the whole thing??

 

[Bt Doctur]

If you didn't see the valve stem sticking up, that means it went into the cylinder and you have to pull the heads

 

[NHGuy]

I wonder if the rocker is taking a wrong angle due to some problem with the pushrod or the guide system, or the stud. Or is there something else like water in the cylinder?

 

[NHGuy]

How old are the exhaust manifolds and risers? Maybe it's good to replace the motor. But why did this one break? You have to know why and make sure the replacement does not suffer the same fate.

 

[yearzero]

It didn't look like the valve fell down, I could still see the stem but even if it didn't fall down it could still hit the top of the piston correct?

The manifolds and risers are less than 4 months old. I replaced them as soon as I got the boat.

 

[Howard Sterndrive]

if the valve is jammed, it probably hit the piston.

if a valve guide is badly worn, exhaust blowing through can harden a spring brittle and then it breaks.

 

[yearzero]

Going to take a look at it closer this afternoon to see if its jammed or not. Quite possible that valve is worn and is killing the spring... The EXACT same exhaust valve spring was the one I replaced last time.

 

[yearzero]

Update: I finally got some time to start tearing into the engine.

Took the rocker off and removed the broken valve spring. The pushrod looked like a rigid noodle. The rod next to it was also bent, I assume from the first rod flying around and smacking it. Oh, Im not worried about the valve falling into the cylinder. It wont budge up or down.

The spark plug anode looked like it was shot off with a .45

Took the intake manifold off and that side of the intake was wet with oil and water. The other side was dry.

Took the exhaust manifold off to pull the heads and it started to get dark but I did peek in the exhaust port. Saw the valve, well the rod part of the valve at least. Looks like the end is broken off and I assume sitting in a puddle of goo atop the cylinder.


Pretty sure that did some serious damage inside that cylinder right? Should I even bother at this point or just start yanking the whole thing and replace the motor?

 

[glenn property of pam]

Update: I finally got some time to start tearing into the engine.

Took the rocker off and removed the broken valve spring. The pushrod looked like a rigid noodle. The rod next to it was also bent, I assume from the first rod flying around and smacking it. Oh, Im not worried about the valve falling into the cylinder. It wont budge up or down.

The spark plug anode looked like it was shot off with a .45

Took the intake manifold off and that side of the intake was wet with oil and water. The other side was dry.

Took the exhaust manifold off to pull the heads and it started to get dark but I did peek in the exhaust port. Saw the valve, well the rod part of the valve at least. Looks like the end is broken off and I assume sitting in a puddle of goo atop the cylinder.


Pretty sure that did some serious damage inside that cylinder right? Should I even bother at this point or just start yanking the whole thing and replace the motor?

Its broke so carry on tearing it to bits.

 

[Volphin]

Yep, sounds like you dropped a valve. Pull the engine. You will probably have a hole in your piston that looks like a shotgun blast.

 

[JaCrispy]

Probably cylinder bore damage as well.

 

[Bt Doctur]

pictures, pictures, pictures, this thread needs pictures

 

[yearzero]

Once Im done with work today Im going to finish pulling the heads off....Ill take some pics but pretty sure its going to be for everyones entertainment at that point...lol.....