engine valve problems

Update: Valve problems definitely caused by rust on valve stems , meaning water is getting from exhaust cooling to enhaust valves. Manifolds, spacers, and risers check out OK, not surprising since manifolds and risers only have less than 10 hours on them. Head and block are fine and are cooled separately by antifreeze mixture. The only source of water into the exhaust that we can think of is leaking gaskets between manifold, spacer, and riser. Risers and manifolds are OEM and exactly the same as the ones which had been removed from the engines and had worked perfectly for years, so it's extremely unlikely that water is creeping back up the risers. Water enterred valve areas at idle at dock, so sudden deceleration is ruled out as a cause. Has anyone had any problem with leaking gaskets causing water injection? Gaskets were replaced each time, but were put on dry, no sealant, as I had done with every other V8 engine I've worked on. I'm considering replacing all eight gaskets on the two engines using gasket sealer on all of them. Comments? Hy
 
About the riser gaskets, what make is the engine? Merc, Volvo or other? Inboard or I/O? The reason why I ask is that there have been problems with some of the gaskets used on certain engines in certain years. I know Volvo for one had a service bulletin on some of their riser gaskets. Did the mechanic use OEM or aftermarket? I'd contact the engine maker and find out were the gaskets ever changed. Since the risers and manifolds are nearly new, that's the main possibility I can think of.
This is why I wish I could still get the OEM one piece manifolds used on the OMC 4.3 V-6s, there is no gasket to leak. When I repower the boat, I am going to either try to convert it to a Merc dry joint system, or get the Hi Tek stainless one piece manifolds. They are extremely pricey but I think they are worth it given what's riding on that one little gasket, with less than a 1/4" of sealing surface width...
 
" i even posted on the Cruisers forum to check what seemed to be a very simple winteriztion. I ran the engines on land while pouring antifreeze into the water feed strainer. "

If you did not drain everything first, you have a freeze crack allowing water into a cylinder.
You mention manifolds, most FWC systems include the manifolds. these would not crack using your winterizing method. They will however crack if raw water cooled and are not drained first before using your winterizing method.
 
As I mentioned before the symptoms point to reversion not injestion. If you have not researched the history of reversion you may be missing out
on the cause
 
Water rusting valve stems to the point that they freeze the valves from working Does NOT happen over night. Not sure of your time frame, but, chances are the rusting valve stems have been going on for quite a bit longer than you're willing to admit. Including your original manifold/riser. They were only perfect because the valves hadn't froze yet. Really have to find out what the mechanic found on the first valve job and what was done? Who did the valve job? Not all modern day mechanics have valve grinding stations.
 
The engines are mercruiser 7.4 inboards. The engines ran perfectly before being winterized in 2012. The boat was not used in 2013. Exhaust valves 1.3.5.7 stuck on the starboard engine at startup in May 2014. Bent and broken pushrods resulted. Port engine ran perfectly at startup. Valve job done on bad head. Engine ran perfectly. Boat taken for fuel and test run, about two miles, and returned to dock. Following week, port engine backfiring. Stuck enhaust valves on both heads.Valve job done. Engine runs perfectly. Starboard engine backfires. Stuck valves on even-numbered head and two bent pushrods. Valve job done. Start engine and backfiring again. Bent pushrod and stuck exhaust valve on number i cylinder. Timeframe from first valve job to last 4 months. Last valve job not yet complete - engine hasn't been re-assembles. Engines are fresh-water cooled so no crack into heads or block is possible. Winteriztion followed Mercruiser manual and verified with mechanics. Does that now satisy everyone on the details? Hy
 
Like I was saying, it would be almost impossible for valves to rust up in that short a time. The valves on starboard engine was probably already rusted up and waiting to get stuck. I wanted to know what the rest of the valves looked like...unless only the bad valves were done. Then you might have valve problems 'til all the valves are done and the water intrusion problem is identified and fixed.
 
All the valves were done on each of the heads. The risers themselves cannot be the cause because they are OEM replacements, had been used for over 20 hours of running time, including my taking the boat across Long Island Sound, and are in perfect condition. I did have to update the number of hours on the risers because I had failed to include the day I spent on Long Island Sound working with a licence=sed, experienced captain learning how to handle a twin-engine inboard and the time it took to move the boat from Momaroneck to Huntington harbor when i first took psession of the boat in 2012. Hy
 
Had to re-read your original post. Now I see the problem that valves were bending AFTER all the heads had valves job done.

Did any of the valves get stuck AFTER the valve job?
 
The last valve job, on the even-numbered valves on the starboard engine was a redo of a full valve job done on that head back in May. It doesn't take much water to cause valve stems sticking so the leakage doesn't have to be large. I'm even afraid to start the port engine again without pulling the valve covers and checking that the valves are all free to move.

What still worries me is that the original valve-sticking problem was discovered at the initial start of the starboard engine, on land, last May. The boat had sat feom October, 2012, to May, 2014. That was enough time for rust to set in. Number 7 valve was stuck and the rod bent. The port engine initially ran great, then developed stuck valves in June, when the boat was finally launched. with tow bent pushrods and one broken pushrod. That engine then received a full valve job on both heads. Then both engines ran great at the dock,unbil a week later,the even-numbered head on the starboard engine stuck. That head received a valve job and at start-up the original odd-numbered head on the starboard engine then had a stuck valve again, this time number 1 rather than number 7, which was bad in the original problem.

I'm still recoverring from some knee surgery so I cannot climb down into the engine bay to begin putting the engine back together. I'm hoping to be able to do that sometime next week, but I do have to be careful. I tend to overdo activity while healing. Once the engine's back together, I have to winterize everything and have theboat shrinkwrapped. I do want to know everything's running right before I put the boat to rest for the winter. Hy
 
What gets me is the valves other than the center valves getting stuck probably means quite a bit of water getting into the manifolds.

Were new guides or sleeves used to repair the old rusted guides?
 
Charlie: Some of the center valves were tight, as well; probably stuck. New guides were installed wherever they were needed. All valves were removed, cleanned, miked and checked and replaced as necessary.. Seats were ground and valves seated. In other words, a thorough valve job was done, as good a job as I would have done years ago when I was a mechanic and our family owned an auto shop. Obviously, I'm far from new to engines, but this problem has me stumped. What makes it doublely perplexing is that the problem is with two engines at different times. Hy
 
you mentioned some training. Did that include a lot of backing??
 
Got me stumped, too. The only other thing that might possibly freeze a valve stem in a guide is galling during initial start-up, no assembly lube, but I'm going way out there with guesses.

Was it in fact, water/rust causing the latest stuck valves
 
The training did involve much backing into the slip, at low or idle speed. The boat ran fine for the 2-hour trip across Long island Sound a few weeks later. It also ran fine the half dozen times we were on the bay in 2012. It ran fine when I winterized it on land. It didn't run fine when I started the engines in 2014. The valves were rusty, up to and including the last head, which had about 20 minutes of running time. Hy
 
Way back in the last century is was common to stuff oily rags in the exhaust outlet. The idea was to keep damp air from the engine. That practice has fallen out of favor and certainly would not account for your second valve failure.

At this point I have lost track of the sequence of events and what was discovered at each inspection. A complete detailed time line might help or just put it back together carefully and cross your fingers.

Did you mill the riser surfaces and check for flatness??
 
When salt water is introduced into a engine the rusting process starts immediately. In as little as 24 hours valves can stick in the guides.
Crank the motor over and you have bent valves and broken pushrods.
Are you manifolds FWC? If not you have cracks in them from your winterizing process by not draining everything first.
 
Yeah, these long posts are hard to keep track of. I think somewhere I read it was a fresh water boat...but I couldn't swear to it, but I was commenting on that assumption.

Valves are alloy so they don't rust like regular steel. I've seen valve seats so pitted from rust that you couldn't make out the seat surfaces but the valves, though being pitted, were no where as bad.
 
Also, Hy, you mentioned the valves were tight. I wondered how tight and how tight they were set during assembly. Valves too tight in the guide can easily gall and sieze.
 
The engine's FWC; the manifolds are not. The manifold I removed for the last valve job was checked by the machinist, using a vacuum setup at his shop, has no cracks in it. The only source of water enterring that I can think of is leaking gaskets between the manifold, the spacer, and the riser.

I did have a slight external leak on those sets of gaskets when I started each of the engines after the last valve job. I had left off the spacers which lock down the oil filter bracket on one engine and didn't tighten the rear nuts sufficiently on the other engine. Those were simple corrections to make. All the gaskets were put in dry, without any sealer. I'm planning on pulling all the spacers and risers and putting in new gaskets again, with sealer this time.

I have an appointment with the surgeon this afternoon to remove the stitches and hope to learn during that appointment when I can resume doing work on the engines. Hy
 
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