Mercruiser 5.7 Locked up?

[sjayjock]

Re: Mercruiser 5.7 Locked up?

I took it to my Local Mercruiser Mechanic to replace the seized Pulley, and pull all plugs to drain and inspect the motor.

They reported to me that the Good news is that the motor survived without damage and ran after all water was expelled, new spark plugs were installed, and new pulley was installed and the motor cranked right up, and no water was found in the oil.

The bad news is that the 4" rubber exhaust tubes feel soft and were most likely damaged due to the excessive heat. Cost was estimated at 27 dollars a LF and so far I know that I need at least 4 LF. Possibly more.

 

[Euro95]

Re: Mercruiser 5.7 Locked up?

Call yourself lucky, the bad news is nothing compared to the good news.

 

[Windykid]

Re: Mercruiser 5.7 Locked up?

Yup you got lucky!

 

[abj87]

Re: Mercruiser 5.7 Locked up?

no cracked manifolds? how did the water get in the engine in the first place? there must be something else wrong.

 

[sjayjock]

Re: Mercruiser 5.7 Locked up?

That is exactly what I asked... I was told that they did not see any cracks and that the water could have gotten into the motor when I stopped abruptly... that it traveled back up the exhaust. What do you think? If there are cracks, will I be able to see them or will they be too small to see? Where should I look? Please advise.

I am very thankful that the motor was drained and cranked up, but I want to be sure that this does not happen again, and that there is no furthur damage. THANK YOU.

 

[drrm123]

Re: Mercruiser 5.7 Locked up?

do you know if engine dieseled when it over heated, if so that how water could have gotten in it.

 

[BLinindoll]

Re: Mercruiser 5.7 Locked up?

I'm wondering if the dealer drained water or antifreeze from the engine? I would hope that they would have noticed if it was coolant, but some mechanics are idiots too! It could be possible he overheated it to the point that he warped the head which would cause coolant to fill some of the cylinders. Sounds like it got pretty freakin hot if he smoked his exhaust couplers.

 

[sjayjock]

Re: Mercruiser 5.7 Locked up?

What is deiseling? How would I know? And why would that allow water to enter the engine.

Also, I am pretty sure that my type of motor does not have coolant in it at all and is water cooled only. I have not noticed any location to add coolant and I have not seen any locations to check for coolant levels. Also I have been through a lot with this motor and have gone through the engines maunal a lot and not seen any indication that it has any coolant, so why would there be any coolant in the engine?

I have read a lot about Cracked Exhaust manifolds, and possibly cracked exausts...The mechanics that work on my boat are very thorough but I am with you, there must be some reason why water entered the engine... I find it very hard to believe that water would travel back up the exhaust this time, I wakeboard everytime I am out and stop a lot, and have been in very choppy conditions, why it didnt happen before is what makes me question there opinion.

Are there checks that I can do to inspect for cracks? And can they usually be seen by eyes or are they too small? Please advise.

 

[TilliamWe]

Re: Mercruiser 5.7 Locked up?

Dieseling is when a motor "turns backwards" a little as you are shutting it down. In a marine engine this allows the water from the exhaust risers to get sucked into the exhaust manifolds and into a cylinder or two.

It is very common for the exhaust hoses and the "exhaust shutters" or "flappers" to melt during an over heat. They are rubber items in the middle of an exhaust system, after all! As I said before, when the raw water pump stops pumping water, the exhaust risers and manifolds are the 1st thing to go dry. So in this case, when you burned up the exhaust shutters, it is very likely that the water travelled up the exhaust system (this is called reversion) and back into the motor. And from what I have seen of inboard ski boats, the motors are mounted low in the boat, so their static line is low, which means reversion is a real possibility, especially when you just melted your shutters.

You'll not be able to see the cracks, if any, in the exhaust manifolds. They will be on the inside. Something you can check is that the gasket between the exhaust manifolds and the risers is intact. Unfortunately, "checking" that means you will have to buy new gaskets and replace them. But while you have the risers off, you can look inside the exhaust manifolds and look for signs of cracks and water, such as rust in the exhaust runners.

 

[BLinindoll]

Re: Mercruiser 5.7 Locked up?

Ah, well that makes more sense that the motor has an open cooling system, which means no coolant and is cooled with water.

This being said, WATER would be in the block and not coolant in your case if the head was warped.

(I assumed it was a closed (uses coolant) system because you said it smelled sweet when it overheated. The reason it would smell sweet when it got hot would be because coolant has a sweet smell when it's hot, water doesn't.)

Anyways....

Now it would make sence that the head warped and the mechanic drained water from the block... because it uses water to cool the engine.

And again, water can only travel up the exhaust if you shut the engine down before coming to a stop. If you just stop quickly while the engine is running, the flowing exhaust will hold the water out and not enter the engine.

 

[sjayjock]

Re: Mercruiser 5.7 Locked up?

Okay, sounds like I should speak with the Mechanics tomorrow. So far They things to cover are:

Warped Head (what is this and how can it be checked?)
Gaskets
Exhaust Manifold for internal cracks

It also sounds like I need to have the engine taken apart to inspect these items... What if any other items should I cover with them or can do on my own?

 

[TilliamWe]

Re: Mercruiser 5.7 Locked up?

First, hook up the garden hose and start the motor and let it run a while. Then turn off the engine and wait 15 second and turn off the water. Then pull the spark plugs to check for any signs of water back in the cylinders. If there is none, you have dodged a major bullet. If there is water, thwn you have to pinpoint its source.
Have them pull the exhaust manifold/risers then. This is not that big of a deal (they are heavy though!) This will allow them to check the shutters, gaskets, and manifolds for cracks.
To "check" headgaskets and heads, they have to be removed. This is a big deal, takes time, and a lot of money! Do this last!
I totally disagree with BL, water can travel up the exhaust, especially after the shutters are gone. It happens all the time, that's why the shutters are in there in the first place.

 

[captmello]

Re: Mercruiser 5.7 Locked up?

I overheated a 350 early this summer. Warped the heads and some valves. Compression test told me that. I didn't have any water in my cylinders, perhaps because I was unable to restart the engine. I might do a compression test on this engine first, unless your mechanic did when you took it in. I fried my exhaust hoses as well but manifolds and risers seem okay. I believe your stuck using a mechanic to solve your problem. With all due respect, if you don't feel comfortable doing the idler pully you could get in over your head pretty fast. Good Luck!

 

[sjayjock]

Re: Mercruiser 5.7 Locked up?

Took out the boat this weekend and ran her hard. Wakeboarded with 3000lbs of ballast filled all day Sat. and Sun. without even a hiccup. In fact, with the new plugs and oil change it ran smoother and stonger than ever.

So far I think I did Dodge a Major Bullet, MATRIX STYLE!!!

 

[TilliamWe]

Re: Mercruiser 5.7 Locked up?

Anyone who has ever gotten a Small Block Chevy hot knows that they can get pretty hot without really hurting anything. Sounds like you just messed up your exhaust shutters/hoses and the motor will be fine. Not surprised.