Bore Honing Without Engine Removal

[Dockhead]

When I bought my boat nine years ago, the Yanmar 4JH3 HTE main engine had only 830 hours on it. It was quite smokey when I bought it, and gave up trying to figure out the cause of the smoking after spending a great deal of effort on it (including torturing the seller before agreeing to close the purchase deal).


Now I think I finally understand the cause -- polished bores from some kind of mistreatment by the PO. I do virtually all my own work on my main engine and rarely have pros on board, but when I had to have the shaft out this spring, I ended up with a really crack pro on board who suggested the real cause, based on a number of factors I hadn't observed, and I believe him.


So now I'm thinking about doing something about it. I think it's gotten gradually worse over the years. The engine starts perfectly and runs like a Swiss watch -- I love this engine. But the blow-by resulting from poor ring sealing is certainly harmful to it, and the smoking is unpleasant, so why not fix it if it's possible?


What is not worth it is to remove the engine and do a complete overhaul. My boat is reasonably well designed for access to removing the machinery, but it is nevertheless a major operation requiring removal of the pedestal and steering gear, cockpit floor, removal of the generator, etc. before you can get at the main, which means $$$$ (or rather, ££££). The engine now has only 3200 hours on it and has excellent oil pressure, doesn't leak any oil, and runs sweet and smooth like a top, so I don't think it needs an overhaul in any case. I would just like to have the cylinders honed and replace the rings and rod bearings, do a valve job while the head is off, and job done. I've done this myself on cars with the engine in place, can it really not be done on a boat?



The hardest part I think will be getting the oil pan off and getting to the rod cap bolts, but I would think that once the head is off, I could disconnect the shaft and engine mounts and jack it up.


Anyone been through this? Words of advice?

[a64pilot]

Bore scope it first to be sure you have bore polishing, before you go through the misery, cause I doubt you do, then if your still not convinced, pull the head, you have to anyway.
Bore polishing exhibits similar symptoms to bore glazing but the cause is very different.
I doubt you have bore polishing, just cause it’s not that old is it? My engine when I bought it was 27 yrs old and had 500 hours, it should have been bore polished, I expected it.
Most of the times what causes bore polishing is excessive storage times without being run, what happens is you get a light film of rust on the cylinder walls when it sits, then every time it’s started, it of course polishes the rust off, repeat enough times and eventually you have worn the cross hatching off of the cylinders and of course they can’t hold oil anymore and get high blow by.
A way to tell blow by is of course to pull the tube loose off of your valve cover, if you have excessive blow by, you will have an almost constant blowing of air out of it, and not just a little air either, it’s a lot, it will carry oil with it, and you should have oil dripping from your air filter if you have excess blow-by, and not just a little oil either.
Even a perfect engine has some blow by of course.
Anyway, if you have blow by, it causes your oil to turn very black very fast and you have excessive oil temps, cause this blow-by is very hot of course and heats the oil up.

Then there is bore glazing, which exhibits the same symptoms, but is different in that the cross hatching is still there, just clogged with a varnish like substance, nearly almost always from partially burned fuel, it’s cause is not getting the engine up to temp to burn this stuff off completely so it gums up.

It can sometimes be relieved to some extent by changing to a very high detergent oil, adding some of your favorite juju oil cleaner and running the absolute snot out of it for a few hours, I mean run it like you stole it.

I would if I were you, do an oil change putting in the Shell Rotella T6 oil, and a couple of bottles of Techron additive, two bottles, not one, and then proceed to run the snot out of it, ideally to windward against some decent seas, idea is to not necessarily to run high RPM, but to put it under a load to drive cylinder pressures and heat as high as possible, but run it full throttle to get there. Unfortunately your Autoprop won’t allow you to really load it up, or I’d tell you to tow something

Another possibility although not as likely is that the original owner was too kind and babied the engine and never seated the rings. I’d suspect though that Yanmar runs their engines on a Dyno before delivery and seats the rings.

Anyway, of course blow-by leads to oil consumption too of course, how high is your oil consumption? If you didn’t have to stop at least once to add at least a quart of oil in You last motoring exercise, I doubt your burning much oil.
Oil of course leave blue smoke in the air that doesn’t dissipate, fuel can be blueish, smells different than oil and seems to dissipate.

Yanmar’s as you know are smoky engines, it comes from incomplete fuel combustion and it leaves many a boat with a nasty, greasy stern, but it’s fuel usually and not oil.

[a64pilot]

If your determined to hone it, it should be able to be done in place, a problem will be if you have enough vertical clearance to fit a real hone, likely you will have to lay the block on its side, almost certainly you will.
For Gods sake, don’t use a dingle berry hone, maybe on a lawnmower or chainsaw, but not a “Yacht” engine.
Your going to have to pull the xmsn as I would want to pull the crank, and I would go back with new bearings.
I have honed many, many engines, and the hardest thing is to get the bores clean after honing to get out all of the worn stone and metal filings out of the cross hatching, some try mineral spirits, some xmsn fluid. I have found noting cleans as well as Dawn dishwashing soap and hot water. There is more to honing than just making scratches, the angle you achieve is important.
Unless I was going through a quart of oil a day, or it was hard starting due to loss of compression or down on power, I would not mess with it, just give it a good “Italian tune up”
No disrespect to the Italians here meant.


Had a Dr in my home town years ago, that had a 911 I think, that was one of the very early ones, and wasn’t likely stock either. He had bought a real hot rod, it was likely cammed etc, built for racing but street driven. Had three two barrel Weber’s, each cylinder had it’s own barrel.
He would bring it to the shop I worked at and we would clean the plugs and the owner of the shop would take it out and blow it out.

The Dr commented that we were the only ones who knew how to properly tune a Porsche. He would then proceed to drive it back and forth to the Hospital every morning through school zones etc until it wouldn’t idle well and he would bring it back.

Now I think about it, they may have been dual three barrel Weber’s

[Cheechako]

It's all about pan removal really. Most boats you can't get it off without removing the engine. I agree it is possible that the cylinders are glazed and a hone and re-ring may get you there.
Is that a turbo? They are infamous for early blow by and ring issues in cars. Other possibilities are the pistons being cracked somewhere on the ring "lands".
When you get it apart, inspect everything very closely.

[Dockhead]

Originally Posted by a64pilot

If your determined to hone it, it should be able to be done in place, a problem will be if you have enough vertical clearance to fit a real hone, likely you will have to lay the block on its side, almost certainly you will.
For Gods sake, don’t use a dingle berry hone, maybe on a lawnmower or chainsaw, but not a “Yacht” engine.
Your going to have to pull the xmsn as I would want to pull the crank, and I would go back with new bearings.
I have honed many, many engines, and the hardest thing is to get the bores clean after honing to get out all of the worn stone and metal filings out of the cross hatching, some try mineral spirits, some xmsn fluid. I have found noting cleans as well as Dawn dishwashing soap and hot water. There is more to honing than just making scratches, the angle you achieve is important.
Unless I was going through a quart of oil a day, or it was hard starting due to loss of compression or down on power, I would not mess with it, just give it a good “Italian tune up”
No disrespect to the Italians here meant.


Had a Dr in my home town years ago, that had a 911 I think, that was one of the very early ones, and wasn’t likely stock either. He had bought a real hot rod, it was likely cammed etc, built for racing but street driven. Had three two barrel Weber’s, each cylinder had it’s own barrel.
He would bring it to the shop I worked at and we would clean the plugs and the owner of the shop would take it out and blow it out.

The Dr commented that we were the only ones who knew how to properly tune a Porsche. He would then proceed to drive it back and forth to the Hospital every morning through school zones etc until it wouldn’t idle well and he would bring it back.

Now I think about it, they may have been dual three barrel Weber’s

I drove 911's for decades. The very first ones (in 1964 and 1965) had Solex, Zenith, and/or Webers. Always one throat per cylinder, as you said. Then they went to Kugelfischer mechanical fuel injection, also with one throat per cylinder. My 2.2 liter 911S's (I had three of them over the years, and sold the last one only a couple of years ago) all had magnesium velocity stacks, too! What a sound they made -- it was music.


As to honing in place -- yes, the really good engineer who was on board this year said the same thing -- that cleaning is the real issue and an obstacle to doing it in place. I had forgotten that he said that



I do the "Italian tune-up" regularly, as it is needed for health in any case. It has not resulted in a reduction of the smoking and blow-by issue, however.



As to taking the crank out -- by the time we do that, then this whole procedure is surely no longer worth it. By then we might as well pull the engine out. The problem is that by the time we do THAT, then we might as well simply repower And I really don't want to do that, with a good running engine with only 3200 hours!!




Some other relevant info:


https://www.pistonheads.com/gassing/topic.asp?t=813639

[Dockhead]

Here is information on the "dingleberry" type of hone:


https://www.brushresearch.com/pdf/GB.pdf


Why do you say not to use them?

[a64pilot]

How much oil is it consuming?
See I think what you want, your not going to get, that is a smokeless mechanical injection Yanmar.
If it ain’t broke, don’t fix it.

[a64pilot]

Give this a try, change the oil and run it 1 gt low.
It is entirely possible that full is slightly overfilled and it is foaming the oil slightly and burning off the excess.
If your uncomfortable with a quart low, try a half a quart low, but I think 1 qt low is fine.

[alaskaflyfish]

The old time aircraft mechanics (circa.1950's) up here in Alaska used to take a handful of Bon-Ami powder cleaner (like Ajax) and stuff it into the intake while the engine was running high rpm. They said it was the best way to de-glase the cylinder walls if the break in process was done inappropriately. I would never do it, but on a old lawnmower,,(humm).. If you do try to hone your cylinder walls, piston and crank out of the block is best. Get a good quality rigid hone that is adjustable to .001 of and inch.

[model 10]

You have no doubt inspected the turbo for the cause of the smoking? How about valve guides or seals?
I would want to know what the problem is before I took it apart. If I were charging you to fix it, I wouldn go on a fishing expedition looking for glazed cylinders on your dime. A bore scope, oil analysis and compression test would come first. There are so many little clues, you could almost know for sure what is going on before you took the plunge.

[captlloyd]

Bite the bullet and pull it, you are going to have it half way apart anyway.

[nhschneider]

Originally Posted by captlloyd

Bite the bullet and pull it, you are going to have it half way apart anyway.

This is exactly what I was going to suggest. I agree that it's premature but it's the best way to ensure that not only is the problem solved but that everything is done right. Then you won't have to worry about it for another five- to ten-thousand hours.

Good luck, fair winds and calm seas.

[George DuBose]

Sticky piston rings? I would try running some Mystery Oil. It is now owned by Turtle Wax, but I think the formula is the same as when it was invented.

You can add MO to the engine oil and the fuel whether diesel or gasoline. I have personally seen several examples of engines that were burning oil and after a few weeks of treating the engine with MO, the burning of the engine oil was definitely reduced.

The only problem with MO is that it is such a good cleaner that a couple of times when I used it on high mileage motors, it caused some of the seals to leak, but that only meant that they needed to be replaced anyway.

I think in your case, it would definitely be worth a try

[jimbunyard]

A page directly from the Yanmar manual for this engine.



Due to the nature of this type of damage, the flex hone is actually preferred over a solid stone hone in this application; the individual 'dingle berries' provide a more uniform cross-hatch on the less-than-plumb cylinder walls.

I think the borescope idea is really good before you start tearing into things. Honing, as you probably know, is a messy as hell job. Hope you have a really spacious engine room if you decide to try this...

[Dockhead]

Originally Posted by captlloyd

Bite the bullet and pull it, you are going to have it half way apart anyway.

As I wrote above, that's clearly not worth it. Then I might as well just repower -- £20,000 more or less -- and that can't be justified in a boat that starts and runs well, and has good oil pressure, and uses little oil, however smoky.


Just leaving it and tolerating the smoke (and blow-by) is definitely one option, if I can't do this in some relatively cheap and quick way.



I appreciate all the good comments about further diagnostic approaches, which I have noted and will do.


I'm still not clear whether it's possible to do what I was asking about in the OP.


Also grateful to Jim Bunyard for the manual page -- showing the "dingle berry" hone in action. Surely that could be used in the engine room. If only I can get the oil pan off and the rods out without spending more hours than it takes to pull the whole thing. If only I can properly and thoroughly clean up after the honing. If, if, if . . . .