'94 Echelon engine failure

[Michigan boarder]

I put a new carb on the boat last week, thinking I was having a fuel issue. Ran it for a minute at idle and like 20 seconds under power and it just got worse. Idled back. Changed the filter and added some gas drier to the tank. Went back out, got even worse. No knocks, no noise, just running erratically like it was missing on a cylinder then not missing then missing again. To the point of the engine not running erratically, but actually just running short of a couple of cyliners, like I had a plug or two fail. Pulled the plugs and I found #5 had the ground electrode beaten down onto the center electrode. Zero compression. After pulling them all, I have no compression on #5 and 20lbs on #3. Here's the data:

#1 - 142

#2 - 150

#3 - 20

#4 - 149

#5 - 0

#6 - 139

#7 - 142

#8 - 135

Looking at this plug, it's beaten down and the texture is rough. Did a valve come loose? I likely have a hole in the piston, correct? The boat has about 650 hours on it. Am I looking at a new engine? I don't have the time to start pulling the heads or anything, it will all have to wait until winter.

[Woodski]

Those numbers imply a head gasket to me as one option, the reason, #3 & #5 are side by side so a blown out head gasket between the two will result in both cylinders being low on compression. A way to tell is via a leak down test or even just compressed air in the hole and listening to where it might be coming out, that will tell you a lot. Does the engine backfire through the carb or pop out the exhaust as when either #3 or #5 is at TDC the other will be have a valve open. That would be the good news scenario and a relatively inexpensive fix ($ for gaskets). Could easily have a couple of bent valves or a bad piston but the two low numbers side by side imply the head gasket is bad. Is the color of the plug a dark grey, if yes that implies aluminum deposits which assuming you have the original cast iron heads, would be piston material. That picture to me does not imply aluminum on the plug but I can't see it really well. Being beaten down does not sound good, that implies something went down the intake.

Would there be any reason the cylinder has injested some water? That can also lead to the symptoms you describe. Head gasket, cracked exhaust manifold, bad exhaust manifold gasket or even bad intake gasket would allow water to enter the cylinder.

Another option could be a broken valve spring, but I would be surprised at two of them. Easy to pop off the valve cover and check for that.

How does the oil look? Does it look like chocolate milk, gotten dirty quickly or changed level oddly? That would be some piston damage symptoms.

Good luck on the diagnosis.

[nuttyskier2002]

The only way to tell for sure is to feed air into the sparkplug hole and listen for where it is going. Into the crankcase means you have a hole in the piston, yes. Into the next cylinder means head gasket. Out the carb or exhaust indicates valves. Something collided with the spark plug and that is not good. Could be a piece of that piston

[nuttyskier2002]

Sorry Wood....I was posting same time as you. Not meaning to steel this thread!

Edited July 8, 2013 by nuttyskier2002

[Michigan boarder]

Thanks for the guidance guys, I'll check that stuff out. I did the plugs and compression and pretty much walked away from the boat disgusted. It's back at the lake and I'll be hauling it home next week. I'll check the oil and the air escape route and report back.

To answer some questions:

• No chance of water getting in. It was bone dry, not even antifreeze was put in for winterizing, I simply drained the water. Easy launch last week at sundown, hasn't even seen any chop.
• Plug is greyish. No aluminum powder on it, but yes it is a dark grey.
• It did not backfire at all when it was running, even at speed. It simply felt like a plug wire was being put on and off (initially). It started right up yesterday and I dled to the launch, no backfires.
• It did get hot last summer when the impellar failed. Not ridiculous, didn't melt any exhaust or anything, but it did get hot (guage at 220).

[jk13]

Hope it's something simple for you.

Surprising there was no noise and that plug got crushed...........I was leaning toward head gasket like Woodski said on neighboring cylinders and even more since you said it got hot last year, but that plug is strange.

Anyway you've got a good start on how to diagnose from the guys. Let us know what happens. Good luck.

[Michigan boarder]

Hope it's something simple for you.

Surprising there was no noise and that plug got crushed...........I was leaning toward head gasket like Woodski said on neighboring cylinders and even more since you said it got hot last year, but that plug is strange.

Anyway you've got a good start on how to diagnose from the guys. Let us know what happens. Good luck.

Yeah, something damaged the plug. I'm expecting the worst. The plug from cylinder #3 looks almost normal. No impact to it, brownish color, etc. When I pulled it out I thought it was OK, but maybe a little darker brown than normal. Then when it only got up to 20 on the guage, I was surprised.

[Michigan boarder]

Another thought. This may be good news. When the engine was still hot, it read 10psi on plug #5. Then I got my boys and was explaining the problem to them...how a 4 cycle engine works, possible damage source, etc. A half hour later, after testing each of the remaining cylinders I went back to #5 again, and this time it read zero.

Can any of that translate into good news? If there was a hole in the piston it would read zero right away, hot or cold, right? If it's still a gasket issue would it change?

Would a broken valve spring allow the valve to impact the piston?

[Woodski]

Per your previous thread, maybe but probably implies that the side of the piston is missing so the oil on the ring land when warm does some sealing. As noted before you tear it down I would either do a leak test or at least plumb some compressed air in to the cylinder to see where it escapes.

Broken valve spring tends to promote the valve introducing itself to Mr. piston unfortunately. Pull a valve cover to check the springs & look to see if the valve tips are at the same height.

[WakeGirl]

That sucks, thinking good thoughts for you MB.

[Michigan boarder]

That sucks, thinking good thoughts for you MB.

Hey, thanks.

Even if it's toast, it could still be a good thing. I spent the day on a Tige Saturday talking with some buddies about "Well, what if it's all shot? What will you do next?" I certainly can't sell it the way it is, what will I get, maybe $4k? So I gotta fix it. Well, if I fix it, then it makes no sense to part with an otherwise great boat with a new engine, so I'd keep it. Well, if I'm gonna keep it, I might as well fix it up right, and add some mods and get another 100hp out of it. So it's a pretty good joke...me pulling plugs and dropping ball bearings in the cylinders just to destroy the engine so I can justify beefing it up to my wife.

[jk13]

So it's a pretty good joke...me pulling plugs and dropping ball bearings in the cylinders just to destroy the engine so I can justify beefing it up to my wife.

Stopped into my old shop one night during some flooding to check over my buddy's Integra that we had pushed out of an intersection--water up to the rockers and floating on each wave from passing cars. One of my other installers was already there with a friend and his 93 Prelude SOHC. Cold air intake was in a bucket of water and they were spraying a water hose at the bypass valve while revving the engine.

"WTF are you guys doing?"

"Trying to hydro-lock it so I can put in an H22, duh!"

"Why not just leave it until the new motor comes in?"

"Got to convince my girlfriend I broke it driving through standing water so she doesn't yell at me."

"Why not just go drive it through some standing water?"

"We tried. Plus we'd have to fix it in the rain to get it home."

"Okay....."

They pulled the plugs and turned it over after each time it stopped running and it sprayed water all over the shop ceiling. Like Caesar's Palace. Took them three tries before it made horrible noises and he drove it home knocking like mad.

Just trying to lighten the mood for you Mb. We're all hoping for the best.

[Michigan boarder]

That's a good one JK! I've given up being angry/depressed. That crap doesn't last long in our house and I had my Saturday night to do that, it's all history now and moving forward.

First world problems: "My boat engine is messed up!" as I sit on the permanent pier of my lake house with my 3 children and wife jumping off the water trampoline...before we grill out and light some fireworks. I'm still glad I have a boat worth fixing!

[AdeL]

Sorry to hear this. Boats are great until they let you down, and then they are great again. Hope it doesn't cost too much to get fixed.

[Michigan boarder]

Sorry to hear this. Boats are great until they let you down, and then they are great again. Hope it doesn't cost too much to get fixed.

Thanks. The worst part is that last fall Woodski mentioned doing a leak-down test, that it could be valve related. I got lazy and thought I'd rule out fuel problems first. Should have listened to the pro!

[Michigan boarder]

Now that summer is over and my work schedule has lightened up a bit I can focus on repairing the boat. Last night I pulled the valve cover. The springs on #3 cylinder are not at the same height. Is this the tell-tale sign? I don't own a leak down guage. Portable compressed air is a PITA based on where the boat is located. I do have good lighting and 110v power and room to pull the head and organize the parts. Should that be the next step, or is there really a benefit to running compressed air into it? I can get the compressor from the shop and drag it over there if you guys think I really should. I am anxious to pull the head and see what is going on.

Edit: cylinder #7 is to the far right, #1 is to the far left.

Edited September 4, 2013 by Michigan boarder

[Michigan boarder]

*cough* *cough*

[Woodski]

Probably, but a couple of things to verify first. Assuming the cam does not have the valves pushed open, what you would be looking at are bent valves. To verify you can do a couple of things, loosen the rocker arms to see if the valve goes to the correct height or slowly spin the engine over to see if the cam is trying to open the valves (I doubt it as it sounds as though the boat has been sitting for a while and the lifters have probably relaxed but maybe not).

If the valves are bent, the question will be why as that should almost never happen in a boat or engine that never sees over 5,000rpm. Hopefully, it is just the cam holding the valve open. Are the springs okay, feel around to make sure they are not broken.

The compression results do support an issue w/ #3 and a bent valve would result in a low compression # (do you recall when you did the compression test if there was an intermittent (psst, or short hiss) noise coming out the carb or exhaust when you were spinning the engine over (that would be a leaky valve). That same noise down in the pan would be a piston.

I still think you have a bad head gasket per your compression #'s...#3 & #5 being low and having the exhaust valves side by side is hard on the head gasket. Pretty simple fix & head gaskets are cheap (Summitt Performance / Jegs or any good hot rod shop has them). Make sure you get the thin ones so you don't lose any compression ratio. You will also need exhaust manifold, intake manifold gaskets and the tstat gasket.

There are some things you will have to know when digging in to a small block, particularly to apply sealant to some of the cylinder head and intake manifold bolts as they break in to the cooling passages or oil passages (simple plumbers putty works fine). Torque sequence is also important to follow. Don't forget to put the engine at TDC and mark the distributor location and the rotor position (you will find if you turn the engine over the oil pump won't move and then it will be out of index and the distributor won't just fall in to place as it is a slot in the bottom of the distributor gear, you will have to spin it over to align). I actually put the distributor back in the hole after I pull the intake manifold off. Other than that, it is pretty simple work.

Edited September 5, 2013 by Woodski

[Bozboat]

*cough* *cough*

I suggest you drink three beers and then go tear it all apart. With my method you will likely end up replacing everything at a total cost of 3x what it should have cost, but you will get it all done.

[Michigan boarder]

Probably, but a couple of things to verify first. Assuming the cam does not have the valves pushed open, what you would be looking at are bent valves. To verify you can do a couple of things, loosen the rocker arms to see if the valve goes to the correct height or slowly spin the engine over to see if the cam is trying to open the valves (I doubt it as it sounds as though the boat has been sitting for a while and the lifters have probably relaxed but maybe not).

If the valves are bent, the question will be why as that should almost never happen in a boat or engine that never sees over 5,000rpm. Hopefully, it is just the cam holding the valve open. Are the springs okay, feel around to make sure they are not broken.

The compression results do support an issue w/ #3 and a bent valve would result in a low compression # (do you recall when you did the compression test if there was an intermittent (psst, or short hiss) noise coming out the carb or exhaust when you were spinning the engine over (that would be a leaky valve). That same noise down in the pan would be a piston.

I still think you have a bad head gasket per your compression #'s...#3 & #5 being low and having the exhaust valves side by side is hard on the head gasket. Pretty simple fix & head gaskets are cheap (Summitt Performance / Jegs or any good hot rod shop has them). Make sure you get the thin ones so you don't lose any compression ratio. You will also need exhaust manifold, intake manifold gaskets and the tstat gasket.

There are some things you will have to know when digging in to a small block, particularly to apply sealant to some of the cylinder head and intake manifold bolts as they break in to the cooling passages or oil passages (simple plumbers putty works fine). Torque sequence is also important to follow. Don't forget to put the engine at TDC and mark the distributor location and the rotor position (you will find if you turn the engine over the oil pump won't move and then it will be out of index and the distributor won't just fall in to place as it is a slot in the bottom of the distributor gear, you will have to spin it over to align). I actually put the distributor back in the hole after I pull the intake manifold off. Other than that, it is pretty simple work.

Thanks Woodski, I always appreciate your input. So, either way, that head has to come off, right? I don't recall a hiss when I first did the compression test, but that was also while it was on a lift and other boats were buzzing around. I've had a few guys go with the same logic on the head gasket, but the question still remains why that spark plug on #5 has the electrode beaten down...something made contact with it. Which again points me to pulling the head. Plenty of reading to do before I dig into it though.

[Michigan boarder]

There are a ton of resources on line, but only a few are specific to removing the heads and including details like what Woodski pointed out with the distributor. Can anyone recommend a good manual to assist me with the heads removal and installation?

Edit: nevermind, found a good one on line for $5.99. '94-97 Mercruisers including Magnum Skiers, I'm good to go with torque specs and all.

Edited September 5, 2013 by Michigan boarder

[Michigan boarder]

I suggest you drink three beers and then go tear it all apart. With my method you will likely end up replacing everything at a total cost of 3x what it should have cost, but you will get it all done.

Unfortunately it's at a building here at work, so no beer. But the radio still works, so that'll keep me going.

[Woodski]

Something hit the plug, no other explanation. It might be partially embedded in the piston, if so you should be able to shine a light down there and see it. But, the head will be coming off regardless.

Are you still running the original cylinder heads? I have a pair of them with only 60 hours. The newer heads all flow much better and will bump the Hp a fair amount. Good time to upgrade if you are interested in doing that and there are several versions around that are a direct replacement so you can save all the old parts.

[Michigan boarder]

Something hit the plug, no other explanation. It might be partially embedded in the piston, if so you should be able to shine a light down there and see it. But, the head will be coming off regardless.

Are you still running the original cylinder heads? I have a pair of them with only 60 hours. The newer heads all flow much better and will bump the Hp a fair amount. Good time to upgrade if you are interested in doing that and there are several versions around that are a direct replacement so you can save all the old parts.

Not sure on the heads, assuming they are original. My new manual has the indentifiers in it, so I'll find out.

Replacement all depends on the damage and the bill. If I'm doing it all - I'm doing it big. If I happen to get really lucky and can do just the heads...not sure. But I will definitely keep yours in mind, good to know.

[Michigan boarder]

Going to remove the head this Sunday and figure out what's up. I've been distracted from boating. Having WAYY too much fun with this: