Mercruiser 6.2L seized up??

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chrishick

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Good morning guys.

We had the boat out yesterday and on the way back in the alarm went off because it was overheating. I put it in neutral and let it idle for 30-60 seconds, then it went from 217 degrees down to about 167 degrees in like 10 seconds like somebody flipped a switch. So we idled through the no wake zone and backed into our slip, which is about a 10 minute ride. The motor was running fine, although I think I remember it was running a little rough right as I was backing into the slip. We get into the slip and I'm attaching the last line to the cleat and the motor dies. I try to restart and it cranks a few times but sounds funny, making a weird clunking sound maybe? I can't really remember the exact sequence, but it reminded me of the few times my old boat had water in the cylinders and hydro locked. Tried one more tie and all I got was a click, like the motor is seized.

This is a 2006 6.2L 320HP mercruiser with a B3 outdrive. The motor has 129 hours and when you open the engine hatch it looks like brand new. This is one of the cleanest motors I have seen for 5 years old.

I pulled the plugs thinking that the motor was hydro locked, but there was no sign of water in the cylinders and I'm still just getting the click. Batteries are fully charged and I've checked all the connections and they are clean and tight.

I honestly don't know where to look next. I've read quite a few threads here on the forums but have not found any ideas.

Does anybody have any idea what this could be? This is a new to us boat and only the second time we have had it out.
 

Bondo

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Re: Mercruiser 6.2L seized up??

Ayuh,.... I guess I'd pull the starter, 'n see if it's Beat or not...
You could wrench the motor over to see if it'll turn over...
Otherwise, Pull the drive to see if it's a motor issue, or drive issue...
 

burp

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Re: Mercruiser 6.2L seized up??

I'd vote for pulling the plugs and use a wrench on the crankshaft to see if you can turn over the engine. If the engine won't turn over remove the sepentine belt to see if the circulation water pump, raw water pump, idler pulley, alternator or power steering pump is frozen up.

Did the audible alarm stop when the water temp came down?
 

chrishick

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Re: Mercruiser 6.2L seized up??

Thanks for the help guys. I did some more tinkering around on Saturday and found the battery terminal was broken off at the starter solenoid. https://picasaweb.google.com/lh/photo/AvUqeleyZC_RGtC3GvB1uMb29EKNgiounvk4P_Bet44?feat=directlink

So, I replaced the solenoid and started it up. It was running rough and sounded like it was missing a cylinder. I could hear a clicking noise coming from the distributor cap. The terminals on the inside of the cap had some kind of yellow corrosion on them. Since I was not able to find a new cap and rotor, I took a small wire brush and cleaned them up the best I could. The motor was still missing on a cylinder. Plug wires 1 and 7 seemed loose at the distributor cap so I pulled wire #1 and started the motor. It ran the same, so I think it is something with #1. I then pulled #7 and it ran much worse, so I think #7 was OK.

At this point I put everything back together and tried restarting. It was a little hard to start, and on the second or third try the new starter solenoid came apart just like the first one did. At that point I gave up out of frustration.

So, I have 3 problems to work through.

1) Replace solenoid again. Why does it keep failing? Is the motor kicking back against the starter motor because of the rough idle and hard start? Is that causing the solenoid plunger to be forced back too far and blows the back of the solenoid out? If I get the motor running properly will this problem go away?

2) Rough running/missing on a cylinder. I'm hoping if I replace rotor, cap and plug wires this problem will go away. Did the overheat maybe have something to do with this problem? All sparkplugs were replaced on Saturday so I know those are good.

3) Overheating. It has done this twice now, both times at WOT. Put it in neutral and let it idle for 1-2 minutes and the temp will drop rapidly from 217-163 in a matter of seconds. I'm wondering if the thermostat is sticking? I have not checked the impeller yet, but that is on my list. Any other things I should check while I'm at it?

Thanks again for any help you can provide on these problems. I'm getting really frustrated with this. We just bought this boat and we spent a LOT of time looking for a low hour (129 hours) boat that was in pristine condition hoping that we would not have any problems for awhile. I know boats are always going to require repairs, but I was hoping to at least get a few trips out before I had to start.
 

Bondo

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Re: Mercruiser 6.2L seized up??

I have not checked the impeller yet,

Ayuh,... That's the 1st place to look,... Not the last....

The solenoid, I donno...
Never heard of an issue like that before...
And,...
Has for the Tune Up,...
Do a Complete Tune Up, 'n Service, instead of piecemealin' it...
 

chrishick

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Re: Mercruiser 6.2L seized up??

Do a Complete Tune Up, 'n Service, instead of piecemealin' it...
Hope I don't sound dumb, but whats involved in a tune up for a fuel injected engine? I thought tune ups where obsolete in the age of computers and fuel injection?
 

joncrisler

Petty Officer 2nd Class
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Re: Mercruiser 6.2L seized up??

EFI engine Tune Up: spark plugs, distributor cap and rotor (if equiped), maybe plug wires. I would take a multimeter and check the resistance of the plug wires before I replace them. Depending on what style they are, they have difference resistance values. Do a 'net search on testing plug wires.
 

chrishick

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Re: Mercruiser 6.2L seized up??

I would take a multimeter and check the resistance of the plug wires before I replace them. Depending on what style they are, they have difference resistance values. Do a 'net search on testing plug wires.
Hmmmm, I think for $80-100 I'll just replace them. Is there any reason to check the resistance if I'm just going to replace them?
 

Bondo

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Re: Mercruiser 6.2L seized up??

Is there any reason to check the resistance if I'm just going to replace them?

Ayuh,.... Only if ya wanta be Perfectly Sure, that yer throwin' away Junk.....
 

joncrisler

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Re: Mercruiser 6.2L seized up??

My best friend is a mechanic at a Chevy dealership (the senior guy), 25+ years experience. A long time ago he told me that the biggest problem in doing a tuneup is that replacement plug wires (especially low-end wires) tend to have very high failure rates. Guy does a tuneup on a reasonably well running engine, and it comes out worse than before: one or more new plug wires is bad, usually at one of the connectors. If you isolated the problem down to 1 or 2 cylinders, why dont you test them first? If you find a bad plug wire, maybe that is your root cause. Now that I think about it, the clicking from the distributer cap would be most likely from a plug wire, coil wire or distributer cap cross-firing to something else. Be carefull around there while the engine is running or you could fry your fingers.

If you do not yet own a digital multimeter, this would be a good excuse to buy one. Cheap ones can be had for $40 or less.
 

HT32BSX115

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10,083
Re: Mercruiser 6.2L seized up??

I'm wondering if the thermostat is sticking? I have not checked the impeller yet, but that is on my list. Any other things I should check while I'm at it?
Howdy,


Probably not. T-stats don't fail all that often (especially in 5 year old engines....)

Impellers......that's another story.

Here's one that is 2 years old with 20hrs on it that came out of my Bravo (it ran "dry" for less than a minute)

DSCN1912.jpg



Not only should you check your impeller, (just replace it) but you should also check for impeller fragments in your power steering and oil coolers that may be from impeller failures that the previous owner might have experienced.....



Regards,


Rick
 

chrishick

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Jul 19, 2008
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Re: Mercruiser 6.2L seized up??

*****UPDATE*****

I replaced the impeller and t-stat. Impeller didn't look too bad, but since I didn't know the last time it was replaced, I have piece of mind now.

I replaced the distributor cap, rotor, plug wires and plugs. The motor still sounds like it is missing on one cylinder. It has a rough idle and will barely stay running at idle. It idles at 500-600 rpms.

I'm thinking I've ruled out spark issues and it must be something with fuel delivery? What other things could cause a rough idle?

Anyone know a good mechanic in the Homestead/Miami area? At this point I would rather just pay a pro than keep throwing parts at it.
 
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