496ho Blew Its Cookies
 

Saturday was a beautiful day on the water, for about an hour anyway! Was running from one end of the lake to the other and thought I would wind it up alittle, at around 4800 RPM "20 seconds" I felt the boat jerk and starboard motor was dropping RPM and stalled. Engine temp. was around 160 and oil pressure 45 PSI. I stopped right away and raised the engine hatch and noticed what seemed to be a small puff of steam belch out of the flame arrestor. I attemped to restart engine and had an uneven cranking RPM along with rattle every revolution. I checked the oil then and it was about 6 inches over full then found the coolant reservoir to empty.
I had read about weak pistons on the 496's on modified engines, has their been much of a problem on bone stockers with 40 hours? I am assuming the piston came apart and went through the cylinder wall. Are their certain year engines better than others?

Anything can break,40 hours is it under warranty?
If so just take it to a mercury dealer.If it did break a piston they will more than likely chang the whole engine.
Water in the oil and cylinders is either a catastrophic failure like piston puts hole in block.Or an exhaust issue and possible hydro lock.

I think you are on the right track....have heard of injectors going bad or clogged..leaning out and killing pistons !!

If a piston broke up it would have gone out with a bang and would not crank over. Pull the plugs. See if one is damaged.

It happened so fast that the antifreeze pouring in the motor never mixed to a milkshake...I have not torn down yet, but with the un-even cranking RPM and deep rattle every cranking revolution it doesnt sound good...I am going to pull plugs and used a friends bore scope and find out....

If it is under warranty you are in luck.

If not... Pull your plugs. If one is chewed up you may as well pull that motor because the show is over. Check the #7 cylinder, a few other guys lost #7 including myself. More than likely a piston imploded then the connecting rod punched a hole in the cylinder wall and sucked the anti-freeze out. Since it sucked in oil & anti freeze at 4000RPM you probably bent a few rods as well.

Here is what it will look like....

Sounds to me like you had a coolant leak in it and hydrolocked it. dont ask me how I know...:rolleyes: pull the plugs and drain all the oil and fluid and then get fresh oil back in it, even run it for a couple minutes with the belt off to get oil circulating, it could be a plethora of things from a gasket either head or intake to something more serious.

I just pulled the plugs and number 1 was smash!

Any idea what is causing the failure....Cast or forged pistons?

They are cast... you might have been lucky and NOT poked a hole in the cylinder or block. If so, you can rebuild with forged or maybe do Raylar kits or something.

I cant tell from your picture. Is that plug melted or a piece of aluminum stuck in there?

It had a piece of the piston hammered into it, when removing the plug it came out hard and cut new threads on the piece of the piston that was stuck in the plug. Im sure it looks just like your posted pictures...The catastropic failure gave no warning at all.
Do they use cast or forged in the remanufactured engine?

Fixx
 

which state you located in? Because i know where their is one sitting in a garage for the pst year, believe its a ho. ill see if i can get yo uthe guys #..

I live in Iowa, thanks!

looks like it ran real lean..ck that injector..and sometime loosing a piston it will still turn over...seen them running before with a rod stuck thru the pan, so you never know...but thats bad...

Personally, I would not reccommend re-using that plug! :evilb:
Sorry dude, bad joke.

Hope you get it going soon. I lost 2 of those engines then Merc seemed to have worked it all out. Guess not. Im going to old school 525 carbed that I can wrench on myself.

Do What???:eek:

Don't they make an additive in a can you could just pour in and fix it?

fixx
 

sorry,my friend lost the guys phone number,,ill see if his uncle can stop by his house and see if its still their and get his number again..

Thanks again, that would be great if someone has one setting around!

If the cast pistons are the weak point on the 496 ho, would I be ahead if I pulled the port motor which runs fine and install forged pistons?

Fixx
 

To be perfectly honest with you, i would get away from the 496's all together,sell the one you have and put the money towards some 500's efi's or check out the replacement 502's that merc is coming out with(they may be out already)..the 496's are discontinued and wont be easy to get parts for in the future..

[QUOTE=mrfixxall;3203939]To be perfectly honest with you, i would get away from the 496's all together,sell the one you have and put the money towards some 500's efi's or check out the replacement 502's that merc is coming out with(they may be out already)..the 496's are discontinued and wont be easy to get parts for in the future..[/QUOTE


What this guy said

Agree I looked at a boat a few weeks ago with 496s and I thought the same thing.After hearing all the piston stories my friend had one let loose also I would only go with blue motors.

I agree also...hard to beat a HP500 simple reliable !!! all this hi tech stuff great...till it breaks, then all your gains just left the building !

Sounds like a good time to get rid of the 496s. I did. Mine found a new home in Germany. This one went in it's place:
http://i763.photobucket.com/albums/x...ng202Small.jpg

Restore I think it is.:party-smiley-004:

Sorry for the luck!

Just freshened a 496 for a customer and he was like why do I have to put forged pistons in they are so much more, now he understands.

blocks can be had and it can be fixed/upgraded

Jim

www.ozarkspeedandmarine.com

32 Sunny with 496HO's running around Iowa. Nick?

sorry to hear that.

-shane

Nick sold his Sunny a few weeks ago...

I dated a girl once who had a formula on the hudson. She would run that thing (496ho) from the GW wide open up river for 10 miles. I'd just shake my head and mumble "ignorance is bliss". I guess I assumed they were bullitt proof. Sorry to find out not. Good luck

Picture of what is left of cylinder #1

I know of one thats forsale, but it's got 340hrs on it...Been absolutely bulletproof...Earlier 496's had forged internals in them...this is a 2002 motor so it might have them?

Some early 496's had a forged crank but I dont think any had forged pistons. From my tribulations with my motors I am finding that very few even had the forged crank. The nodular crank is actually pretty good up to 700 HP.

The cast pistons however.... suck! They are the root of almost all problems with the 496's

I suppose a couple bucks was saved to install junk pistons! What a shame...I was thinking of upgrading the power but I would need better drives than the b1x's...I dont think I want to spend that kind of jack now!

Sorry to hear about your 496 failure on a 40 hr. 496.
Let's not "Throw the Baby Out With the Bath Water"
When you consider about 50,000 - EFI 496's are out there in the marine world from all manuafacturers and maybe 100 or so have failed similarly and many of them from supercharging stock motors its not really a problem engine. This translates to a failure percentage of about .2% which is awesome by any standard.
Not to knock or bash blue engines by any means, if there were 50,000 blue engines out there I guaranty there would be at least the same number of failures from marine performance usage as I am guessing sure about 50-100 - HP525 engines have grenaded (1% - 2%) since their 2002 introduction and Mercury Racing has only distributed about 4,000 of these engines which would be a lot higher percentage of failure. When there are less of an engine out there you hear less about issues or problems.
Everyone is quick to blame the hyper-eutectic piston in the 496 (8.1L ) engine when in fact the piston in such large usage in large quantites of engines does very well with many 496's over the 700 -1000 hour mark and still going strong. When you consider how many kit 525HP Raylar 496's are running just fine with the same pistons you can see that the piston is not the biggest problem just one of the problems that appears in some cases where I suspect fuel delivery was the real cause of failure not structural piston failure.
I think everyone in the marine industry considers myself at Raylar to one of the industry's leading experts on the 8.1L 496 engine and as such I can tell you from all of our years of work with the 496 and developing parts and engine builds for this engine that that the 496 (8.1L) efi electronic engine is more durable and reliable than any marine engine that has ever been released in similar quantities.
It is obvious that when a hyper-eutectic piston fails it can have catistrophic effects on the engine at rpms and loads, your picture of that cylinder is a perfect example of that, however sometimes the failure of a forged piston can do similar damage at speed under load.
What all efi engine boaters need to pay more attention to and be careful of is the condition of their fuel pump, filter systems and related injectors on the newer efi engines.
With winter weather storage conditions and the higher concentration of ethanols in todays fuels, the buildup of WATER and MOISTURE in these efi fuel systems is at EPIDEMIC LEVELS! and when the fuel supply is leaned to the cylinder at speed under load the combustion temperatures climb so fast and are so destructive to the piston that these failures are getting more common.
Word to the wise here, carefully winterize your engines, service and replace all fuel system filters and discs, especially in the Merc CoolFuel III systems (those on the 2003-2009 Merc 496's.)
I don't think its an overkill thing to check your fuel sytem pressure at the fuel rail under full load in the boat running at speed at the first of the season and make sure the fuel delivery is not showing reduced pressures from fuel delivery issues. Some of the new fuel system cleaners and additives may not be a bad idea for those in the colder winter storage areas. You don't nearly hear of as many of this piston failure in the warmer regions of the country and world, yes a few, but my expierence seems to show that this failure do to fuel lean burn and resulting detonation and damage is about 5 or 6 times more common in these regions or where the boat owner did not properly service the fuel system yearly or do careful winterization methods.
In any event are forged pistons for the 496 engine stronger, you bet ,especially the ones Raylar has developed and sells for this engine. Can they or any other forged piston suffer damage and failure from fuel delivery problems, you bet, see and hear about it all the time!
Again, very sorry for your engine damage and loss and if Raylar can be of any help with a new redo for that engine or parts for your redo, let us know, we would do our best to make sure the replacements would be stronger than your stock 496 engine.

Hope my information and insight here can help possibly save more boaters from engine damage such as this.

Best Regards,
Ray @ Raylar

service and replace all fuel system filters and discs, especially in the Merc CoolFuel III systems (those on the 2003-2009 Merc 496's.)


Ray
what fuel filters does a 496 have besides the spin on fuel separator and what discs are you talking about?

Thanks

They are in the fuel pump box if its cool fuel.Not the side with the regulator the other.Loosen the screws in pull the handle the disc is at the bottom and the filter is in what cam out you have to twist the cover.

hi can you help my fuel cooler is on the right hand side of motors standing at front looking towards back can you tell me if i have these dics twin 496ho 2001 as i would like to renew if i have them allso wot would the correct fuel/p be at WOT 47 psi seems to ring a bell thanks paul from England ps great response makes perfect sense ray

While You're At It
 

It's a good idea to replace your spin on filter with the Raycor S-3213.

If you have the newer "box" where the lift pump, pressure pump, and both filters are all installed inside that one box, install the Raycor somewhere in line BEFORE the box.

This will help prevent you from struggling to get any water and debris out of that box. Really not a very good design in terms of maintenance.

If you've ever tried to clean one out ya know what I mean.

Having the clear bowl makes it nice to see what's coming out of your tank...