Bore glazing again

Re: Stand by for incoming

Yes I have and I did not like it at all, they are very noisy. We have an Aerogen 6 which is a high output one with multiple blades that isn't noisy even close up. Our club marina insists that visitors with Airmarine types tie them off for the duration of their stay so it is very much a recognised problem of noise nuisance.

I'm not campaigning about noise though, this was a legitimate post about bore glazing and it was a side comment really about engine noise in an anchorage. That said we were in Camaret one time when a German yacht on the next buoy ran his engine continuously for the entire 24 hours he was there! I have no idea why but it sure was noisy, it was a big engine and pumped huge amounts of water out in big hissy bursts from the exhaust. Note it was not the engine noise but the exhaust noise that irritated.

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Re: Stand by for incoming

Why would they call you a stinkie! Proper generators are usually much quieter than main engines because of better exhaust control I believe. Actually, thinking about it, having a separate generator on a boat that already has twin engines must be an argument that running big engines light is bad for them, otherwise why add another expensive engine for charging?

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Re: Stand by for incoming

Gennys are far quieter, than running mains, especially inside the boat, I havent seen any main engines, wiith soundproof covers.

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You cannot be serious!

Glaze busting or re-honing abrades microscopic grooves nearly transverse to the cylinder axis. The purpose of these is to provide lubricant beneath the piston rings and thereby prevent metal-to-metal contact. As the engine wears, these grooves gradually disappear, accelerating the wear process. This is markedly increased by poor air filtration, allowing ingestion of hard particulates such as clays and sand. The axial scoring caused by hard particulates bridges the transverse grooves, allowing the oil to escape from them. Poor air filtration is one of the best ways to reduce engine life.

Tipping Ajax into the incoming air will intensify this process many times over. I don't know the hardness of the abrasive in Ajax but it's almost sure to be harder than grey iron piston rings and bores.

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Re: Stand by for incoming

Your right. I see how it could look like I was having a go. My apologies. I was just thinking about the guys in Pwllheli with their big Fairline power boats that fill up and thrash over to Ireland. It takes £750 in diesel each way!
That much diesel would keep me going for 6.5 years at my current yearly mileage!

This isnt ment to be a dig at power boaters either. Every one to their own.


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Hi vyv and others,

I am not english speaking so bear wih me.

vyv quote of "reading marine course" has it wrong.

The lower rated and the higher rated engine differ only in the duration of max period for max revs.

For instance I have a 80HP 912 aircooled Deutz in my boat, but that is at 3000RPM which is for automotive use only.

For continious operation, the engine is rated at 2800 RPM only and delivers 75 HP only, but can run at this rev and full load indefinately.

Further, a Diesel's rev's and power is only controlled by the fuelpump rack and governor usually running at half the engine speed. One can actuallu see on a bosch pump what revs the governor is set. if it says 13 that means the max revs are 2600RPM.

A Diesel alway gets full air supply (except the 220D from years gone by had a butterfly valve to generate a slight vacuum for the ignition advance and a brake booster which is now done with a vacuum pump on the alternator in a Toyota for instance), so running a diesel on low load will inject less fuel for a lot of extra air and have a cleaner combustion, no carbon deposits and shows no black smoke from the exhaust.

Under full load, most Diesels will start smoking black because the air in relation to the injected fuel is not enough, carbon is formed excessively and all related bad chemicals to go with it.

Theoretically, this should not happen as when engines are new, the maximum amount of fuel is carefully set, but with age and certain loss of compression, air intake and overall efficiency decreases and the diesel runs too rich and may need an adjustment to make the pump deliver less to prevent smoking.

Another point is, that a 50HP engine rated at this output at 4000RPM, will have about 10hp at idle, now drawing 2 x 100 Amps from two alternators at 12 Volt will be about 2.4KW or about 3HP. So the engine would run not without load, but with about 30% of its rated output.

Now some practical observations. Where I live, gensets on Farms are still very common. From 2 to 6cyl aircooled Deutz or Lister, the 3 Cyl with about 30HP driving a 20 or 25 KVA alternator the most common. At 1500 RPM, these gensets see quite some load during a few hours during the day, for occasional welding, turning, runnig a washing machine etc., but after hours, for illumination and running a TV only, there is virtually no load to speak of in relation to the engine size.

A friends parents got a Lister 34 years ago for their wedding, it was running every day for about 12 hours with loads as outlined and was never overhauled so they assure me.

My landlord, where my boat is on the dry presently, has a truck and diesel workshop and says glazing is not a problem that he is aware of, and he is, so everybody says, the most knowlegable man on the subject of diesels in our sparsely populated country.

Another thought, Tractors with power take offs, sometimes drive negligable small loads for long periods and left idle often on farms during the day because of faulty batteries, that is no problem either.

regards ongolo


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ok im a cynic

yup temperature is king, optimum engine temp no probs, condensation not a prob therefore nasty acids dont form, optimum temp = optimum combustion.
(thats why petrol engines need chokes to get enough light ends to ignite properly)
in all my years rebuilding engines from little two strokes to 16 cylinder turbo - supercharged detroit diesels i never, never had to diagnose "oh that one needs a rebore or cylinder liner change cause its got bore glazing" however when i got an engine to rebuild and just needed to fit new rings or piston and rings, i would as a matter of course, "bust the glaze" on the cylinder with some fine emery and oil, this was so the new mating surfaces would be able to wear into each other.
my thoughts are that the raw water or air cooled donks which are not as easy to temp control as a closed water system habitually are run too cold. too cold means that condensation appears in the enclosed area of the engine, acids can then form
also combustion is not complete when the engine is too cold and i suspect that deposits from that incomplete process cause other deposits and both these processes cause premature wear,
it is that that cause sliner and piston probs, any glaze on the bore is a naturally occurring process over a long period of time.
to sum up
run your engine often and also for a long enough time so that it reaches optimum temperature.
if it doesnt heat up quickly look to your thermostat or temperature control system, the failure to reach operating temp quickly is what will shag your engine.
to go on to oils, the manufacturer wil know what suits the engine, however in the case of rebadged ones or "industrial ones" does the original manufacturer really know what temp his rebadged one is going to work at?
stu


<hr width=100% size=1>http://www.beneteau-owners-association.org.uk
 
Re: You cannot be serious!

he's taking the piss, dont take any notice (i think!)
stu

<hr width=100% size=1>http://www.beneteau-owners-association.org.uk
 
Re: I\'m bored & glazing over again

As Stu says the operating temperature is important but I am not sure that it is in so far as the oil is concerned as long as the viscosity is such that it flows properly at the engine's operating temperature - I would have thought a multigrade would look after that. Flow when the engine is started and if it takes along time for the engine to get up to operating temperature would be a concern and I understand that synthetics have better characteristics at those low temperatures.

In our own case it is academic because the engine is indirectly cooled and the only ventilation of its compartment is from the induction air - it runs plenty warm enough.

John

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Re: I\'m bored & glazing over again

OK you lot. So if bore glazing doesnt exist, why have I got it?

My engine is a fairly recent 20hp raw water cooled diesel driving a 34 ft 4.5 t boat. The engine has never - not even for a minute - been idled to charge the batteries. To the contrary, it has been worked hard including some long wind free passages of 30 hrs. Yet when we last had the head off, the bores were like a mirror and the oil consumption was 1 litre every 12 hrs running, with the oil being seen as a slight exhaust slick rather than blue smoke. No synthetic oil has ever been near it - just SAE 30 in CC/CD.

Incidentally, glaze busting only relieved the problem for a short while. Valve seals and guides OK.

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Re: I\'m bored & glazing over again

How about it is because you have not run it enuff with NO load?

John

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Re: You cannot be serious!

My apologies Vyv – my suggestion was more of a tongue in cheek response. A bit of garbage that I must have picked up somewhere or other.

Your reply was both interesting and informative though and reminds me of a friend that used to race speedway bikes professionally. He had to strip his engine after every race because of the cinders etc getting into the engine via the air intake. He also used to complain of sand granules getting into the carb from the petrol refining.


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Re: I\'m bored & glazing over again

That is not bore glazing, that is bore polishing. Could be a few reasons, not crosshatch honed properly or styicking rings or wrong oil or wrong temperature. But not bore glazing, which is a varnish like substance on the bores, dont get the two confused.

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Re: You cannot be serious!

Who knows maybe he was. As a Cadet I once watched a Glascow 'engineer' rebuild a boiler fuel oil pump, and on finding it stiff simply filled it with fine grinding paste and muttered something about 'gawn'g ahore to find his ole' which as a teenager from the SouthEast I did not understand fully at the time.

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Re: You cannot be serious!

We did in my army days have an instant decoke mix, which we would mix from avgas, parafin, brake fluid, which we would rev the engines up to the stops, with the air cleaners off, then pour quickly about a gallon of this stuff down the inlet, the engine would cough as lot, then huge clouds of steam, carbon smoke etc would pour forth from the exjhausts, after which the engines would run sweet! I once did this and the engine was still crap, and a compression test showed worn vales, so off came the head, the valve seats did need re-grinding, but the head, pistons etc were spotless! It works! A pint would do for baby engines, of about two litres capacity max.

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Re: From me plant using days

I'd think that it's not whether there loaded or unload but whether they're being thrashed. Diesels like to be run in the top third of the rev band. Sailors liking a quite life run them well below that for much of the time. My little 1GM10 over gases if I run it in gear and at high revs which I'm putting down to a prop to hull speed miscalculation.

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Synthetic oils

have been developed to match the higher temperatures of turbo-charged, high performance diesels. (ignoring the similar ones intended for petrol engines). The higher operating temperatures and high flow rates of these oils at the pistons lead to considerably higher oxidation rates, to combat which the oils have relatively high base numbers.

When oils with high base numbers are used in normally aspirated engines, at lower temperatures, the high base number leads to increased wear rates and ultimately bore polishing.

I have owned Yanmar, Bukh and Kubota marine engines. Each manufacturer has recommended lubricants with highest grade CD, and CC as an alternative. Personally, I use CC if I can get it, increasingly difficult. These grades are all obsolete now, being replaced by CF4. I don't know much about that grade and have never used it. I'm a little suspicious of grades that state themselves to be suitable for turbo or non-turbo engines, so I shall continue to use CC or CD for as long as they continue to be available.

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Re: Synthetic oils

Hi Vyv

We have the same problem about CC and CD oil and the CE and CF has disappeared also so I have used a non synthetic Mobil oil with claimed service categories CG-4/CF-4/CF now for about 80 hours I guess (the CF oil disappeared just recently).

I have spoken to Mobil here in NZ plus they have a very good internet site which makes recommendations for various engines - our is a Volvo Penta and the CG-4/CF-4/CG oil is claimed to be the one and claimed to be approved by Volvo. But like you say, I am wary, especially when the engine manufacturers are saying CC or CD in their manuals (in fact they say don't use CD for the first 20 hours in mine - a 1996 Volvo).

One thing I try to do is not cruise at the same revs all the time - don't know if it helps, but it makes me feel as if I am at least doing something to help!

Regards

John

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Running in reverse

Last time I ran my engine in reverse on the mooring - I dragged it! Decided that this mooring wasn't heavy enough and moved to Plymouth! I did apply the full 75 horses to it.

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