poorly built merc block, is this normal?

[JT!]

i recently bought a boat with a blown motor.

it had a cracked casing, small fix right?....it needs crank bearing.

well upon disassembly i found the cause of failure. millions of black beads.
these beads have pitted the #1 piston so bad it looks like it boiled the metal. they are embedded in the ports openings in each cylinder.

also all the intake and exhaust ports are 10-50% blocked by casting ridges, as thin as paper, which easily disintegrate. i am not impressed.

the motor is a 1987 mercury 70hp 3 cyl.

now what? anyone i can talk to at merc? (do they even care?)

 

[CharlieB]

Re: poorly built merc block, is this normal?

lol

You said it....... you bought a blown motor.

That piston DID boil, at least the piston dome tried to boil off as it was being burned. Crush a couple of those beads and you will find that they are made of burnt aluminum, as is the casting flash that you describe.

You have a job ahead of you, to clean all traces of the fried alum out of the cases and cyl's, then determine how far you are going to have to bore the cyl's to get a good surface for oversize pistons and rings.

Ensure the carb's are perfectly clean, chances are one got too dirty and leaned that cyl too much and caused the melt down.

Install a new water pump kit and rebuild the fuel pump, and you'll have a new engine again.

Patiences and attention to detail, you'll be fine.

 

[JT!]

Re: poorly built merc block, is this normal?

got a full engine gasket set. incl fuel & water pumps.

i plan to do a full restore.

the cylinders are in good shape. it was the rod that took the hit.
i will replace the boiled piston and look at the suspect carb.

i will also check cylinder bore size & roundness.

i'm looking for a rod #638-9002 or #638-8532 anyone PM me if you have spare parts for this engine

 

[hamit59]

Re: poorly built merc block, is this normal?

you can try these two links to help in finding your rod and other parts .i would check the bore closely as you can only bore to +.030 max by the book. i hope this helps
hamit
www.eastcoastmarineservice.com www.mercruiserparts.com

 

[JT!]

Re: poorly built merc block, is this normal?

im planning to buy a micrometer and get those cylinders checked. i need the block cleaned of metal debris anyways, so its a good time to decide on the bore it if needed BEFORE i order pistons.

whats with the block though? full of metal beads embedded in each cylinders' intake port wall? only 1 piston was boiling, i dont think it spread that stuff that evenly.

and all the casting debris on the seams is attrocious, it was more than 50% blocking the exaust port exit to lower unit. wth. was there absolutely no quality control in 1986 when they built it? the edges of the cast residues are very brittle, and break on the touch (or at least bend)

21 yrs later can i show them this horrible block and actually get a response? can i email them and send pictures?

thanks

 

[Laddies]

Re: poorly built merc block, is this normal?

You can contact Mercury Marine with a problem but first think, do you really believe that engine ran like that for 21 years with what you believe is a defective block or is as Charlie says debris from the melt down.

 

[JT!]

Re: poorly built merc block, is this normal?

spent the day today cleaning up the block.

going to polish up all the ports, clear out the casting 'films' or 1" tall ridges, whatever you call them.

the beads being aluminium seems plausible, except how did they get into the intakes on the other 2 cylinders?

i'd say theres a total of 1/2 cup's worth of these black beads, yet the piston hasnt lost that much metal, theres maybe 20 pinhole sized boil marks. there are hundreds of beads.

(update) the beads are iron or something, they can be picked up by magnet.
and its really hard to see the port blockage in the 2nd picture, but its there.

 

[JT!]

Re: poorly built merc block, is this normal?

anyone have a clue where these iron beads came from? the block and pistons are aluminium.

the sleeves themselves are iron, but are not damaged in any way.

 

[JT!]

Re: poorly built merc block, is this normal?

any clues where the beads came from? i spoke to a nice guy at shorty's marine and he suggested it came from my reeds. they look good.

i am about to put the motor back together after polishing and porting it. no real mods but will most definitely help it's holeshot, by removing all the casting obstructions.

i need to find the source of those beads.

 

[Chris1956]

Re: poorly built merc block, is this normal?

JT, The only ferrous items on that motor are bearings, piston ring pins, rings, wrist pins and clips, cranks, sleeves, reed petal stops and fasteners. it is time for an inventory of these components. Could the beads be needle bearings from a wrist pin? How about carbon mixed with aluminum, or some wierd alloy?

Could they have been injested thru the carbs, from the outside worid?

the reeds are stainless and not usually subject to the temperatures necessary to melt 'em. You should also be able to see any reed damage.

 

[CharlieB]

Re: poorly built merc block, is this normal?

Need more pictures

MAGNETIC?

Can you crush these beads?

Set a few on the anvil portion of a vise annd roll/press/twist on them with a hammer, see if they will crush, if not then hit them, CAREFULLY, you don't want any to fly out sideways and hit you in the eye.

Try to determine of these are steel or a carbonish residue from a very hot combustion, such as melting/burning off a heavy layer of carbon from piston dome(s).

Molten material coming from one cyl melting down will 'reverberate' out one exhaust and get pulled back into another, cool and deposit. It gets EVERYWHERE, and quickly, one cyl can melt down in just seconds and lock up a motor.

But magnetic, that's a tough one. I'd be looking very carefully at that rod/bearings for heating/damage.

 

[JT!]

Re: poorly built merc block, is this normal?

let me replace the word beads with grains


these specks are not uniform in size yet all are smaller than a grain of salt.

it looks like grains of silt, used in molding cast metals, that was painted over with factory paint.

there is also larger sized debris painted onto the surface of the heads, inside the water jacket.

 

[Yepblaze]

Re: poorly built merc block, is this normal?

Looks like the guy that did the block cleaning took the day off.

 

[CharlieB]

Re: poorly built merc block, is this normal?

The magnetic part is what throws me.

No iron or steel is used in casting a block, they are either sand cast of lost foam castings. NO steel or iron unless a cyl melts down, melts a ring, fire cuts down a cyl wall, melts and smears rod bearings and specks fling off, cooling and solidifying on contact with cooler surfaces. Building up in ports.

Wish I could see more of this.

 

[JT!]

Re: poorly built merc block, is this normal?

they look like gunpowder.

its found in each lowerside intake passage in block. the damaged (top) cylinder has less of this stuff in it than the lowest cylinder, which is in top shape.

the rings are all intact and square edged. all parts are original, no previous history of anything, not even a carb or waterpump.

its 21 yrs old but doesnt have more than a couple hundred hours use, if that.
It was however poorly maintained resulting in failure.

the cylinder walls are glazed and brassy looking (rust? burnt?) i am thinking of honing, hoping to not have to oversize it.

i cant find a cheap micrometer so i was thinking of taking it to a local 2 stroke machine shop. any fancy things i should know about honing or boring a 1 piece head & block. can i assume a shop that does MX racing cylinders is able to do these 1-piece blocks?

 

[jkoce]

Re: poorly built merc block, is this normal?

cheap micrometer: http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=7914

better micrometer: http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=97389

 

[JT!]

Re: poorly built merc block, is this normal?

it needs to be an 'inside' micrometer, to be able to access the center and upper wall diameter readings.

 

[BR]

Re: poorly built merc block, is this normal?

Here's a thought about the "grains" which are attracted to a magnet...Have you considered that the motor could have been submerged or left sitting for some time without any winterizing and that a coating of rust developed on the internal ferous parts (cylinder linings, needle bearings, etc.) and that what you are seeing throughout the motor is the dispersion of those rust particles? The stuff that looks like it was painted over is probably just covered in carbon & byproducts of combustion. Lots of gunk can accumulate on the exhaust side of an older motor especially one run without proper maintenance. Just my .02

 

[jkoce]

Re: poorly built merc block, is this normal?

it needs to be an 'inside' micrometer, to be able to access the center and upper wall diameter readings.

aye, just use the two prongs on the back of the micrometer to get an ID reading.

 

[JT!]

Re: poorly built merc block, is this normal?

Here's a thought about the "grains" which are attracted to a magnet...Have you considered that the motor could have been submerged or left sitting for some time without any winterizing and that a coating of rust developed on the internal ferous parts (cylinder linings, needle bearings, etc.) and that what you are seeing throughout the motor is the dispersion of those rust particles? The stuff that looks like it was painted over is probably just covered in carbon & byproducts of combustion. Lots of gunk can accumulate on the exhaust side of an older motor especially one run without proper maintenance. Just my .02

its in the intake boost ports. semi-plausible, but hard to believe they could migrate backwards from the cylinders into the intakes.