Worn Piston Ring on my Merc 4.3l TKS

[jdwarns]

Location: Annapolis, MD
Boat: 2006 Tahoe 215 I/O
Engine: V6 Mercruiser 4.3l TKS
Engine Serial: OW344165
Drive: Alpha I Gen II
Drive Serial: OW591396

I started to notice poor acceleration and excessive blow-by this season.
Worn piston ring(s) the likely culprit.
Dry compression test indicated 180 PSI for all cylinders except #3, which checked in at a mere 50 PSI.
Wet compression test on #3 yielded full 180 PSI compression.
Now pretty confident that a worn piston ring is the culprit.

And now for the part where I ask for help ...

Service shops won't give me a free estimate for replacing piston rings, even if I bring the boat to them. They wouldn't even give me a ballpark $1k range for the job after I promised I wouldn't hold them to it... come on, it's a pretty standard job when I can give you all the engine info. I'm hoping several people here have had to get this work done by a mechanic and can chime in with how much it cost them, or at least how many hours it took the mechanic so I can estimate the cost myself. My guess would be about $1K give or take a few hundred ($750-1,250)?

I'm only considering a mechanic for time's sake. I always do my own work on my vehicles and boat, but this job would require me to pull the engine and likely cost me the season, as I have never done internal engine work before.
I know I could do it, and do it right, but it would be a major effort.
With that being said, it wouldn't take too much encouragement, verbal and/or liquid, to convince me to do it myself. Hopefully some people here have done this work themselves and can provide the right amount of encouragement/discouragement to help me make my decision.

Here are my thresholds... if I can get it done by a mechanic for about $1k, I'll do that. If it would cost much more than $1k, I'll do it myself and not worry about possibly missing this season.

Thanks in advance for your help. I LOVE this forum!

~ Jesse

 

[Dakota47]

Re: Worn Piston Ring on my Merc 4.3l TKS

may as well rebuild the motor new bearings & all .. pull the motor yourself & take it to a machine shop for complete rebuild.. total cost around $1.000

 

[Don S]

Re: Worn Piston Ring on my Merc 4.3l TKS

I would start it up, run if for a bit to burn the oil out of that cylinder. Let the engine cool down and try it again. I don't buy the compression coming up 130 lbs with just a bit of oil.
More likely a stuck shrader valve on your compression tester.
But I sure wouldn't tear down a 5 year old motor for one compression test reading.

 

[45Auto]

Re: Worn Piston Ring on my Merc 4.3l TKS

If your one cylinder truly did come up from 50 to 180 PSI with a wet test, it's not just the rings.

 

[jdwarns]

Re: Worn Piston Ring on my Merc 4.3l TKS

Thanks for the quick replies. I should have specified I checked dry compression on cylinder #3 three times. It was the second cylinder I checked. I checked it once... 50 psi. I zeroed the compression tester and tested again... 50 psi. I then tested the remaining cylinders and they all read 180 psi. I came back to #3 and it read 50 psi again. I'm all about check/recheck.
I probably should have also mentioned that I had a slight problem with the cooling system and the engine reached a temp of probably 180-200. Not sure if this would be hot enough to cause early piston ring failure?

 

[Don S]

Re: Worn Piston Ring on my Merc 4.3l TKS

Automotive runs with 210? thermostats in them, you 200? is no problem at all. It's just too hot inside a closed engine compartment with little air flow for cooling (like UNDER your car)

Just run it and recheck, you may have just washed out a chunk of carbon blocking a valve. Unless you just have a strong desire to take your engine apart to find nothing.

 

[jdwarns]

Re: Worn Piston Ring on my Merc 4.3l TKS

I would LOVE to not have to take my engine apart. I don't think a blocked valve would explain the excessive blow-by, but it's definitely worth checking/rechecking a few more times before pulling the engine. Thanks again for the replies.

~ Jesse

 

[81 Checkmate]

Re: Worn Piston Ring on my Merc 4.3l TKS

A piece of carbon deposit could very well keep an exhaust valve slightly open and cause it to not hold pressure in the chamber.

Carbon deposits are like small rocks!

Just a Thought!

 

[guyaverage]

Re: Worn Piston Ring on my Merc 4.3l TKS

That would cause low compression (and probably lower than 50 psi) but that wouldnt explain the excessive blowby, or why the wet compression test raised the pressure so much.

My non-professional guess is that you have water going into #3 and it corroded the cylinder wall and piston rings. I'd see if you can get a shop to put a borescope in there and see if they can see what the cylinder walls look like.

If by my lucky guess that is the problem, you still need to figure out why or how water got in there, and fix that problem too.

Good luck, hope this works out so that you can salvage the summer season.

 

[fossill]

Re: Worn Piston Ring on my Merc 4.3l TKS

Unless you're eager to depart with your hard earned cash take it out on the water and give it a good hard run. Then do your compression check again, (throttle wide open and crank a good five revolutions....but you know that).
Take a good look at the plugs too and compare them a chart if you're not too sure what you are looking for. Seen many a good engine torn down and nothing found.
If you're going to rip it down, make sure you rebuild it top to bottom complete or you're really wasting you cash.

 

[Bondo]

Re: Worn Piston Ring on my Merc 4.3l TKS

My non-professional guess is that you have water going into #3 and it corroded the cylinder wall and piston rings.

Ayuh,... Or detonation blew enough piston away from the ring lands....

Throw a rebuilt long block into it, Yerself, for alittle over $1500. or so...

Ya can blow Air, into the cylinder at Tdc, to verify the rings, or valve thing...

Btw,... Most Important thing is to Diagnose,....
Exactly what happened, 'n Why....

To many guys come on here cryin' 'bout their Smoked brand new motors, cause they didn't fix the underlyin' issue that Smoked the original motor...
Poor fuel/ fuel delivery is the #1 cause of detonated motors...

 

[Fun Times]

Re: Worn Piston Ring on my Merc 4.3l TKS

Location: Annapolis, MD
Boat: 2006 Tahoe 215 I/O
Engine: V6 Mercruiser 4.3l TKS
Engine Serial: OW344165
Drive: Alpha I Gen II
Drive Serial: OW591396

Thanks in advance for your help. I LOVE this forum!

~ Jesse

Are you aware this engine should still be covered by MPP Platinum Protection. (Mercury Product Protection - Platinum). This engine should be covered until 04/18/2013.
http://www.mercurymarine.com/servic...otection/mercury-product-protection/overview/
http://docksidemarine.com/Page.aspx/pageId/73330/Platinum-Coverage.aspx

Someone must have anticipated having some kind of problem with this engine to cover it so long.

You just need to make sure the engine is transferred into your name. Good luck.

 

[StevNimrod]

Re: Worn Piston Ring on my Merc 4.3l TKS

My thinking is that it would be almost impossible to give you any meaningful estimate. You simply don't know what it needs until you take it apart. You could assume EVERYTHING internal needs attention and be able to say it won't be MORE than a certain amount, but that's not meaningful either.

The problem with a shop just replacing the rings is that they're hanging their reputation on a job that might be half cocked. In a lot of cases the customer asks for something specific, you go through all the warnings and legal jargon, and when it doesn't work out how they wanted it to they run around town badmouthing your shop. Nobody wants to that, and with the backlog most places have this time of year it's not worth the hassle.

As far as your Merc warranty, understand that it only offers coverage "for mechanical and electrical failures caused by a defect in material or workmanship." Determining your failure was a result of defect in material or workmanship is always the point of contention and frankly depends on who you're dealing with.

 

[jdwarns]

Re: Worn Piston Ring on my Merc 4.3l TKS

I totally understand a shop not wanting to give me a quote to fix the engine until they can identify the full scope of the work needed. I wasn?t asking for a quote to fix it. I just wanted a ballpark for the ?what if? case? If I pull the engine and bring it to the shop and it IS just a worn piston ring, about how much would it cost to replace the rings, hone the cylinders, etc.

I also understand a shop not just agreeing to do what the customer wants. If the work the customer wants done won?t fix the problem, but the shop performs only that work anyway, the vast majority of customers would absolutely blame the shop when they discover their problem hasn?t been fixed. Most people are just chomping at the bit to write a bad review. Believe me when I say my sympathy goes to the shop for having to deal with so many miserable morons day in and day out. I just want a ballpark estimate for the ?what if? case and I?ll totally understand if they rip it apart only to find that it?ll require more than just replacing the piston rings.

I was tempted to write all this up in my initial post but didn?t want to clutter it up. Just understand that I?m a reasonable person, but I understand that a shop has to assume that I?m not . That?s why I posted here to try to get a feel for how much people have spent on getting new piston rings installed assuming nothing else was wrong.

Thanks again to everybody who has responded.

 

[Bondo]

Re: Worn Piston Ring on my Merc 4.3l TKS

That?s why I posted here to try to get a feel for how much people have spent on getting new piston rings installed assuming nothing else was wrong.

Ayuh,... It appears you don't understand that JUST piston rings are not just replaced...

Replacing the piston rings is a small part of Rebuilding the block...

The cost, 'n hassle of gettin' that deep, can't justify ONLY replacin' Just the Rings...

 

[jdwarns]

Re: Worn Piston Ring on my Merc 4.3l TKS

OK, so I just retested. Compression is back down to 50 psi.

I should also clarify my wet compression test? My spark plugs are mounted horizontally and it was pretty difficult to fit my funnel into the space and curve the tube into the spark plug hole. I wound up dumping more than just a few tablespoons of oil in. I?m not sure how much made it into the chamber, but it was probably enough to mask a rather large problem.

I should also state that I?m the third owner of this boat and there are signs of a previous overheat. The paint on my portside riser (same side as my #3 cylinder) has quite a bit of bubbling and rust on the top. The paint on the rest of the engine is immaculate. My temperature sender was also malfunctioning. My gauge would read 180 when the infrared thermometer indicated the thermostat housing was 160 (where it should be). I replaced the temperature sender and it now reads the correct temperature. I also had to resolve an issue of poor water flow through my portside cooling system when I bought it. I?ve taken extremely good care of it for my three years of ownership and have done all the necessary winterizing/summerizing work, but I can?t undo an overheat from a previous owner, if in fact an overheat occurred.

I still think it's possible to just need new piston rings installed, along with cylinder honing before re-seating the new ones, without a complete rebuild with all new parts. Piston rings can wear without causing collateral damage if caught soon enough. With that being said, I think I've got more than just a worn piston ring on my hands. I think I need to take a look inside to see the condition of the piston and cylinder.

It might be time for a long block, huh?

 

[Bondo]

Re: Worn Piston Ring on my Merc 4.3l TKS

It might be time for a long block, huh?

Ayuh,... See post # 11...

 

[jdwarns]

Re: Worn Piston Ring on my Merc 4.3l TKS

Ayuh,... See post # 11...

Sorry, meant to credit you with the long block suggestion but forgot.
Also, I agree that diagnosing what happened is extremely important to prevent it from happening again. The more I think about it, the more I think there's enough evidence pointing to a serious overheat at some point that caused damage to that piston/cylinder.

 

[Bondo]

Re: Worn Piston Ring on my Merc 4.3l TKS

Sorry, meant to credit you with the long block suggestion but forgot.
Also, I agree that diagnosing what happened is extremely important to prevent it from happening again. The more I think about it, the more I think there's enough evidence pointing to a serious overheat at some point that caused damage to that piston/cylinder.

Ayuh,... From yer story, I'm still leanin' to Detonation...
But,...
A forensic tear down is in order to know for sure...

 

[Don S]

Re: Worn Piston Ring on my Merc 4.3l TKS

The more I think about it, the more I think there's enough evidence pointing to a serious overheat at some point that caused damage to that piston/cylinder.

As I mentioned earlier, 200? temps will not damage the engine. Things like improper timing, lean fuel/air mixture at speed, vacuum leaks, etc. can lead to piston damage.
Here are a couple of pages from a service manual to help explain. Note: Many times the edges of the piston melt off and you can actually see a lot of the ring.

http://forums.iboats.com/attachment.php?attachmentid=97654&stc=1&d=1307811924