Tore down powerhead pics and questions

orangeman · Apr 6, 2009

Tore down my 1982 115HP inline 6 because there was play in the crank shaft. It actual wore away the tip of the timing pointer. It appears to be in generally good shape but I have a few questions.

1: 2;nd piston from bottom has a broken ring. The only damage I can see from this is a chip in the piston along the ring grove. first picture shows this. Should I replace the piston or will this one be OK? Do I replace just the broken ring or all 3 rings.

2: The bottom cylinder was dry but the other cylinders had oil in them. The head is dry and grey. Does this indicate any problem? Is this cylinder running lean? See pic 2

3: Both endcaps have areas where the outer bearing race is that look polished. The bearings slide in easily but are snug without noticeable play.
See pic 3.

4: I plan on replacing upper and lower bearings and the broken piston ring. Anything else I should repalce/ inspect while i'm in there. Pic 4 shows the crank assembly.

I'm a noob so any advise is appreciated

matt9923 · Apr 6, 2009

Re: Tore down powerhead pics and questions

If i were you while you already at it i would bring the cylinders to a shop and have them measure them and see what they say. Maybe lightly hone them and get new rings or keep hem how they are. Or bore oversize buts that's a lot more money. I would replace that piston and all rings on it. You should at least hone and re-ring all of them it will be a lot better.
Matt

daveswaves · Apr 6, 2009

Re: Tore down powerhead pics and questions

orangeman said:
Tore down my 1982 115HP inline 6 because there was play in the crank shaft. It actual wore away the tip of the timing pointer. It appears to be in generally good shape but I have a few questions.

1: 2;nd piston from bottom has a broken ring. The only damage I can see from this is a chip in the piston along the ring grove. first picture shows this. Should I replace the piston or will this one be OK? Do I replace just the broken ring or all 3 rings.

You need to replace the piston, a new one will come with rings and a rod pin and retainer clips. When you are this far in it makes no sense to put a damaged piston back in.

2: The bottom cylinder was dry but the other cylinders had oil in them. The head is dry and grey. Does this indicate any problem? Is this cylinder running lean? See pic 2

Not running lean, you probably have a water leak in the exhaust baffle/water jacket that is steam cleaning your lower cyl. You will have to either repair or replace the part that is warped, corroded away, or cracked. You will be able to see it once you get the water jacket (side of the engine, not the plug water jacket) off. It is two pieces with a gasket inbetween and I can pretty much guarantee there is a hole or crack in the baffle plate down by number 6.

3: Both endcaps have areas where the outer bearing race is that look polished. The bearings slide in easily but are snug without noticeable play.
See pic 3.

I assume your bearings are toast based on your original description of crankshaft play. The endcaps are probably OK, they just took some wear and the bearings might have caught and spun in the endcap. Make sure the new bearings fit snug.

4: I plan on replacing upper and lower bearings and the broken piston ring. Anything else I should repalce/ inspect while i'm in there. Pic 4 shows the crank assembly.

I'm a noob so any advise is appreciated

You are going to have some difficulty re assembling the unit, special tools are required to hold the rings while you re insert the pistons in the block. If you do not have them you may be able to rent or borrow them from an older merc service shop. If you do not use the tools you will break rings when you put it back together.

Faztbullet · Apr 6, 2009

Re: Tore down powerhead pics and questions

If you had that much end play, I would check both the upper and lower caps or replace them. The crank has to have some end play(I forget spec), thats the reason for shims under top housing. If yours had no shims and this much play replace both caps and check rods as they be worn with to much side throw.

OldMercsRule · Apr 6, 2009

Re: Tore down powerhead pics and questions

Looks like water intrusion in the bottom cylinder, ya need to stop that.

Is that same rod also rusty or am I dreamin'?

JR

orangeman · Apr 7, 2009

Re: Tore down powerhead pics and questions

Thanks everyone for the replys that's exactly the input I was looking for.

Tonight I will open the water jacket go looking for leaks and report back tomorrow. The rods are not rusty they all have a brown/red paint on them.

The endcaps did have 1 shim on the top. I have the factory manual which gives a procedure for checking end play that I will use when I reassemble. My issue seemed to be more axial play. The top bearing did not appear to have issues but I damaged it during tear down and will replace. The bottom bearing has some noticeable slop so I think that was more the problem. With the water intrusion that makes sense to me. Anyone have a tolerance for the endcap bores. How would you inspect them?

Is there a procedure for checking the center main bearings. Do I just rotate them and go by feel or is there a a procedure to follow?

Thanks again
Orange

OldMercsRule · Apr 7, 2009

Re: Tore down powerhead pics and questions

orangeman said:
Thanks everyone for the replys that's exactly the input I was looking for.

Tonight I will open the water jacket go looking for leaks and report back tomorrow. The rods are not rusty they all have a brown/red paint on them.

Then me eyes aren't werkin' right; or me brain cell is broken.

The last rod on the far right of the pic that you posted has a distinctly rustier color then the other five do.

Maybe it was trick photograhy eh? JR

The endcaps did have 1 shim on the top. I have the factory manual which gives a procedure for checking end play that I will use when I reassemble. My issue seemed to be more axial play. The top bearing did not appear to have issues but I damaged it during tear down and will replace. The bottom bearing has some noticeable slop so I think that was more the problem. With the water intrusion that makes sense to me. Anyone have a tolerance for the endcap bores. How would you inspect them?

Is there a procedure for checking the center main bearings. Do I just rotate them and go by feel or is there a a procedure to follow?

Thanks again
Orange

...

orangeman · Apr 7, 2009

Re: Tore down powerhead pics and questions

Ok did my homework. Opened the water jacket and there is no obvious leak anywhere. No cracks and I'm assuming if it was leaking around a bolt or through gasket there would be some minearal deposits or rust to give it away. What do you all think? Could it be a leak in the lower crank seal that is the source of the infiltration. If the bearing was sloppy I would think it could compromise the seal.
The only damage I found was where the exhaust exits the block and I assume that is not much of an issue. Pictures are attched let me know if you see anything.

Droll · Apr 8, 2009

Re: Tore down powerhead pics and questions

daveswaves said:
You are going to have some difficulty re assembling the unit, special tools are required to hold the rings while you re insert the pistons in the block.

No need for special tools to insert the piston on this engine, just insert the pistons into the block one at the time, when they are all in you can put in the crankshaft...
"Glue" the rod bearings in place with grease, then attach one rod at the time...

Not "by the book" but works fine, on the older style rods tool might come in handy thou ...

Ok did my homework. Opened the water jacket and there is no obvious leak anywhere. No cracks and I'm assuming if it was leaking around a bolt or through gasket there would be some minearal deposits or rust to give it away. What do you all think? Could it be a leak in the lower crank seal that is the source of the infiltration.

Well water has entered the lower cylinder, you need to find the surce....

It could be the lower seal as you pointed out...but do a close inspection for cracks or damage in the gasket surface .

New seals #26-41953
Complete gasket kit #27-85653A87
Upper bearing #30-62567T ( SKF 5206 )
Lower bearing #30-63742T ( SKF 6206 )
Main bearing needle #29-714221 you need 112

RESTRICTOR #66517 you probably needs up to five, they are NLA but some dealer might have them...

Is there a procedure for checking the center main bearings. Do I just rotate them and go by feel or is there a a procedure to follow?

Remove the reed cages and inspect the labyrinth seals, ANY mushroom and the closest main bearing needs replacement....

When the main bearings start to go the crankshaft starts to flex more... until it starts to touch the labyrinth on the reed blocks...

Arne Kjetil

deerhuntre · Apr 8, 2009

Re: Tore down powerhead pics and questions

Droll, two questions:

Could you describe what the 'labyrinth seals' are or can you post a picture?

Also, in your signature, the link for 'Mercury L6 ,Rebuilding a Tower' is not working, and I'd love to look at your pictures and progress.

--Bill

stackz · Apr 8, 2009

Re: Tore down powerhead pics and questions

I would not re-use that chipped piston. few problems that come to mind is it will create wobble in the new ring and possible just break the ring again. or you could get detonation from the shallow spots causing a hotspot on the piston top surface. surprised it didnt gall the cylinder wall with that much missing.

as for special tools to put the pistons back in. only thing you'll need is a piston ring compressor, they are like $10 at autozone. the one I have I can use on pistons as small as the one in my lawnmower and as big as the one on my diesel truck.

Droll · Apr 8, 2009

Re: Tore down powerhead pics and questions

deerhuntre said:
Droll, two questions:

Could you describe what the 'labyrinth seals' are or can you post a picture?--Bill

Here can you see the labyrinth seal, when the bearing gets worn, the crankshaft will flex some and start wearing the aluminum...( you get mushroo )

Also, in your signature, the link for 'Mercury L6 ,Rebuilding a Tower' is not working, and I'd love to look at your pictures and progress.

Are located at my private server, having some uptime problems...:redface: , try again now ??

Arne Kjetil

Droll · Apr 8, 2009

Re: Tore down powerhead pics and questions

stackz said:
as for special tools to put the pistons back in. only thing you'll need is a piston ring compressor, they are like $10 at autozone. the one I have I can use on pistons as small as the one in my lawnmower and as big as the one on my diesel truck.

Don't think you can use that type in an inline engine, since this type of engine doesn't have loose heads ( blidbore ), pistons are inserted from behind.

If your doing this "by the book" with the proper tool.... ALL pistons are mounted on the crankshaft first, then ALL pistons are inserted into the bores at the same time....

But if putting in one piston at the time, you can just use your firger to hold in the rings......

Arne Kjetil

deerhuntre · Apr 8, 2009

Re: Tore down powerhead pics and questions

So where in the world can we get a replacement rod for this sort of rebuild?

All the rest of the stuff seems to be available here on iboats. But I can't seem to find a rod. (Mine broke, and I really appreciate this post and all the photo's and information in here!!)

--Bill

Droll · Apr 8, 2009

Re: Tore down powerhead pics and questions

deerhuntre said:
So where in the world can we get a replacement rod for this sort of rebuild?

You would have to find some used rods as they are NLA from mercury....

If you search Ebay or other sales sites it's easy to find them

....

You will have to indentify your type of rods first ( old or new style )

Top rod are a OLD style rod, uses a nut & bolt, got the casting number 622 5667 ( vissible on one side of the rod )

Bottom rod are a NEW style ( or cracked style ), uses a bolt only, got the casing number 624-7943 .

Bouth types can be used in any inline 6 engine ( DC type 1972/73 > 1988 ), but all 6 rods should the same type .

Arne Kjetil

orangeman · Apr 8, 2009

Re: Tore down powerhead pics and questions

Hey Droll really appreciate you taking the time to help me out. Couple of questions:

-What is a Restrictor I'm not familiar with this part?

-Do you have an opinion on reusing the piston vs replacing?

-Are Sierra parts OK or should I be looking elsewhere?

Orange

Droll · Apr 8, 2009

Re: Tore down powerhead pics and questions

orangeman said:
-What is a Restrictor I'm not familiar with this part?

Hard to explain with few words...

POOR IDLE CONDITION -CYLINDER BLOCK BLEED RESTRICTORS
(Attach Service Bulletin Sticker on Page 1B-1 3 of Your Service Manual.)
Merc 1500-1400-1350-1150-850, 800 (excluding 1969) and 650 (3-Cyl. 1972) models have a nylon
restrictor in the intake passage of each cylinder, except the lower cylinder. (Figure 1) Purpose of
this restrictor is to aid in the prevention of
fuel puddling in the intake passage. Should a
poor idle condition exist in any of the above
outboards, check intake passages, as restrictors
may be missing. Replace a missing restrictor
with Part No. A-66517.

The restrictor itself are a nylon tube

( 3 mm long and 2.5 mm in diameter, with a tiny hule... ), location see picture

Restrictors may or may not be in place, it there's a 2 mm wide hole into the cylinder ... it's missing

Do you have an opinion on reusing the piston vs replacing?

Got no problems with reusing pistons IF they are within spec and got no damage... but would use NEW rings.

-Are Sierra parts OK or should I be looking elsewhere?

Sierra parts are fine.

Replacement pistons can be:
Mercury
Sierra ( Persan pistons )
ProMarine ( Persan pistons )

Stay away from Wiceco..

Arne Kjetil

orangeman · Apr 8, 2009

Re: Tore down powerhead pics and questions

Thanks again
My 1;st post has a picture of the piston with a broken ring and a small chip at the top of the top ring groove. Assuming I should replace this one.

I removed the center reed block and see no mushrooming, looks undamaged. The other 2 reed blocks I am having trouble getting the screws out without striping. Is there a trick to loosening the locktite?

The water jacket gaskets are a PITA to remove. Any tips for scraping them off without damaging the mating surface?

Orange

Droll · Apr 9, 2009

Re: Tore down powerhead pics and questions

orangeman said:
Thanks again
My 1;st post has a picture of the piston with a broken ring and a small chip at the top of the top ring groove. Assuming I should replace this one.

Yes .

The other 2 reed blocks I am having trouble getting the screws out without striping. Is there a trick to loosening the locktite?

Loctite will loosen up if applying heat...

Best way to loosen those screws....put the crankshaft back in the block, use an impact screwdriver with the correct bit .

The water jacket gaskets are a PITA to remove. Any tips for scraping them off without damaging the mating surface?

I am usually using a sharp blade ( those loose blades you just cut of the tip to get them sharp again ).
Just take the time

Arne Kjetil

orangeman · Apr 9, 2009

Re: Tore down powerhead pics and questions

I went and bought a larger screw driver and got the reed blocks off. The bottom reed block does show a little bit of mushrooming. I will try to get a picture of it tonight. So now I will replace the rollers in the lower bearing but uppers should be OK. Does the reed block need to be replace?

Orange

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