Why I like boating on the SoF

[Portofino]

It’s well documented on rigs etc diesel generators run at low loads need overhauling ( opening up ) a lot sooner than those under load .
Back to boats that’s why bigger boats JFM s territory have two different size genys .So its easier to match predicted load to the machine . eg a 10 kva and 30 kva in the same boat .Not 2 x the same size .Of course one runs 24/7 , so unlike the main engines they soon rack up starship hrs .

 

[jakew009]

Why do you say that ?

Big difference between idling with no load vs running under load but at low revs.

I’ll probably get slated for this, but the problem, whilst it exists, is massively over exaggerated.

Assuming the engine is otherwise in good health, and is using a decent, clean oil, the problem of bore glazing is not a real in a modern engine.

Just let it rip occasionally and make sure the oil is changed once a year.

 

[Portofino]

We’ve made a quick dash back from Cannes to Sanremo, weather is far better here but not looking good for the next few days.

We have dashed back to CH for few days as storms / clouds forecasts .Will rtn to boat later in the week when the sun pops out again.

 

[MapisM]

View attachment 162802

OK, that particular statement is indeed almost identical also in the V engines manual.
But aside from sounding like something written for the sake of being politically correct and careful about environment (which is arguably laughable, but... Hey-ho!), it has absolutely nothing to see with what was being discussed.
What I was referring to when I said I never came across a written recommendation of any engine manufacturer against, is the actual boat usage (i.e., cruising) with engines at low RPM/load.

 

[Portofino]

Big difference between idling with no load vs running under load but at low revs.

I’ll probably get slated for this, but the problem, whilst it exists, is massively over exaggerated.

Assuming the engine is otherwise in good health, and is using a decent, clean oil, the problem of bore glazing is not a real in a modern engine.

Just let it rip occasionally and make sure the oil is changed once a year.

It’s not bore glazing , only you have mentioned that .

I think the bigger issue is with CR injection tip failure .

As far as sooted up oil we don’t really do the hrs leisure boaters and as you say an annual oil change freshens up that aspect .Oil is cheap insurance .Assuming everyone’s using manufacturers spec oils when I say this btw .

As far as low loads at tickover , 600 rpm ,the EGTs drop to under 200*c and even at say a reasonable D speed 800 rpm they barely reach 300*c despite shoving the boat along at 9 + knots .They reckon 500-650 *c is optimal .Some run at the higher end , Volvo over 600 *c and some MAN just under say 560 *C .There is about a 100 *C range .

We are not CR , so for me I am not 8hitting myself as my injectors are old ( ish ) school , and I believe as you infer a good “ let rip “ cleans them up .

Also if there was an issue even with one I would be able to see it by comparing the EGT s , load and fuel burn rates and maybe a difference in jacket ( that’s your water temp ) between sides .

In reality yes MAN saying avoid tickover for more than 5 mins is sometimes un achievable, say hovering awaiting berths or fuel pontoon queues or marina approaches and manoeuvres .

But the jist if understand it ,is inline with what DAW has telegraphed on this thread .

There are some quite good American marine engine forums and FB groups they are all in agreement on this

 

[Portofino]

OK, that particular statement is indeed almost identical also in the V engines manual.
But aside from sounding like something written for the sake of being politically correct and careful about environment (which is arguably laughable, but... Hey-ho!), it has absolutely nothing to see with what was being discussed.
What I was referring to when I said I never came across a written recommendation of any engine manufacturer against, is the actual boat usage (i.e., cruising) with engines at low RPM/load.

Assumption is the engines are matched ( signed off by said manufacturers) to the boat and it’s intended usage .

If you want some other use of a P boat then why not buy it get a SD or full fat D hull ?

I visited S/Skr factory way back 2005 now and they had a Pred 95 in build with a pair of John Deere motors .
Buyer wanted to take it for a yr long cruise ( with crew ) all over the Med at D speed .
Money wasn’t the issue , but no point bespoke building it with triple Arnesons zillion Hp V 16 MTUs , that empty the tanks every day .Idea was go to bed and crew would chug it overnight to next place .Oh yes it had fins too ,

Anecdotally a few yrs later I bumped into the sales guy the shower + rounder at Cannes and we reminisced, he told me after the yr was up it was a 8ugger for brokerage to sell it on .As back then Pred owners all wanted the other way max speeds bigger engines .

Back on this side topic low rpms running .Our ( leisure boaters ) hrs are so low that, basically you are reducing say a 15000 hrs opening up / overhaul time in 1/2 to 7500 hrs and if you sold it with 3000 on that did under 900 rpm it’s pretty irrelevant. So it’s all pretty hypothetical due to low hrs .Except perhaps if it’s a CR and holed a piston before 1000 hrs in your 4 th or 5 th yr ? Out of warranty.

 

[MapisM]

I don't disagree

Assumption is the engines are matched (signed off by said manufacturers) to the boat and it’s intended usage.

I don't disagree at all with that.
In fact, these days, also because my favourite anchorages are just round the corner from my marina, practically I never use the boat at D speed anymore (after 17 years of trawler boating!). She just goes too well at 20kts, and even better at 25, so why bother?

That said, I also agree with jakew009 that the potential problems deriving from "underusage" (so to speak) are hugely exaggerated.
I mean, engines in need of rebuild at 2000 hours spent working very hard to spin Arnesons are not unheard of, but I've yet to hear of any marine engine needing an early rebuild due to a too light usage.

In fact, I rest my case about never having read any engine manufacturer formally recommending to avoid such underusage, also in their light duty rated engines with the highest power and RPM for any given block - not to mention other commercial ratings, of course.

This doesn't mean I'd buy a S/skr for cruising at single digit speed, anyway - even if fitted with smaller engines!
That's bound to be the choice of someone only interested in pose value, as opposed to logic/functionality.

 

[jakew009]

The US army did an interesting study to investigate whether idling engines for long periods made any difference to their longevity.

I’ve attached a screenshot of the summary page, in case you can’t be bothered to read the whole report. But the gist is that it makes f*** all difference



Full report: https://apps.dtic.mil/dtic/tr/fulltext/u2/a151273.pdf

 

[piratos]

View attachment 162802

It will be the lower EGTs , poorer ring fit , excess oil betting burnt as the rings let more through .Plus contamination the other way soot , abrasive particles getting of un properly burnt fuels ( 350 *C as opposed to 560 *C ) down past the loose rings and adding grit to the oil .

You could shorten the oil change Fq to mitigate ?

Also as I said earlier it’s the crap sticking to the injector cannuli which is risky .knackers the spray pattern up .
Not so much with old fashioned tips like you and me have , more so with CR set ups .

I guess this refers to idling only and not under load as mentioned displacement speed at 8-900RPM ??

 

[Portofino]

I guess this refers to idling only and not under load as mentioned displacement speed at 8-900RPM ??

It’s pretty linear .Idle under 200 , low load 8-900 rpm is 300 *c .
Optimal for MAN s high 500s , VP I think a tad over 600 *c This is what you ought to aim for imho these sort of temps .

The study that Jake kindly published post #148 is pre 1984, so basic injector tip architecture, and ran for approx 100 hrs
Also “ conservative service procedures “ I think I touched upon more Fq lub changes already further up .
Folks will have to judge there own relevance of this dated paper to todays CR machinery .

At the end of the day simply consult your individual manufacturer, or franchised tech and figure out the least worst regime to run your boat diesels .DAW did it .I did it ( franchised tech ) told me run @80 % load avoid under loading, low loading .
Bear in mind DAW and myself are at different ends of the spectrum , him new CR with a warranty when new , me 2004 , so 20 yr old in excess of 1000 hrs pre CR …..but the msg was the same .It’s called convergence .

Its pretty multifaceted marine Diesel engine failure we are just touching low loads influence .

If there’s no agreement that’s fine your engines ,you do what you like with them .

I found a link from a stateside tech below brings in a few other facets , particularly todays CR thingy .


MAN s MTU

The reason the MANs are so smokey at idle is that they use sequential turbocharging and INSANE boost pressures.

This in turn requires lower than usual base compression numbers so that the cylinder heads don't come up through the salon floor at full power...... result: low power smoke.

MTU pumps use a bronze impeller like on the MTU engines. For example the MTU series 2000 raw water pumps are notorious for causing damage that could have been prevented. The pumps are built with an external weep hole that lets you know if the water or oil seal is leaking. If the pump is leaking raw water and the problem is not addressed on time, the leaking raw water will corrode and seal the weep hole shut. The leaking raw water will not have an exit now and will start flowing through the oil seal leading to the interior of the engine. Many overhauls have had to been done as a result. Therefore its strongly recommend the inspection of the raw water pump to be done often.


Injector tips CR

Probably the most damaging area affected by entrained air/vapors is the engine's fuel injectors. One of the functions of diesel fuel is to lubricate the injectors as they are working. As the entrained air/vapor passes through the
injector it is not providing complete lubricity.
This lack of lubrication for the injector's barrel ad plunger becomes even more critical with the tight tolerances and high fuel pressures used in today's injectors. The entrained air/vapor creates a metal on metal situation. Over time the plunger can start to stick and as it wears, factory tolerances are lost. This causes fuel blow- by in the injector. According to Caterpillar's handbook, entrained air/vapor can create up to 50% greater forces by the plunger on the injector tip. As the fuel comes out the injector tip under high pressure the entrained air/vapor can also act much like an acetylene torch, eroding the injector tip. These two things in combination can lead to the injector tip breaking off."

Injectors
Fouling due to solid deposits inside a diesel fuel injector or its nozzle is an important problem experienced with diesel fuel injectors. This phenomenon arises during injector aging and consists of a series of chemical reactions whose products are deposited on the external and/or internal metallic surfaces of the injector and/or nozzle. Diesel injector fouling deposits can be broadly categorized as injector nozzle deposits and internal diesel injector deposits (IDID). The latter are also referred to as internal injector deposits (IID).
The factors that affect injector deposits basically fall into three categories: (1) properties and chemical composition of the fuel properties, (2) local fuel temperature of the geometry and (3) the injector nozzle and internal fuel wetted surfaces.
Properties and Chemical Composition of the Fuel. Fuel characteristics such as high viscosity, low volatility and reactivity of the unsaturated hydrocarbon chains (olefins, aromatics), can facilitate carbon deposits at the nozzle holes and the formation of protuberances on the injector nozzle tip. The presence of small traces of Na, Zn, Cu, and Ca in the fuel (metal contamination) has been demonstrated to significantly intensify nozzle fouling as well as internal injector deposits .The additive package dispersed in the fuel also has an important effect on metal contamination and more generally on injector coking.
The presence of biodiesel in the fuel can also impact injector deposit formation. In some cases, depending on its detailed composition, biodiesel can have little impact on the accumulation of injector nozzle deposits . In other cases, biodiesel can contribute to the formation of injector deposits. Not only does biodiesel contain trace metals that can intensify injector deposit formation, biodiesel oxidation products can contribute to deposit accumulation. Carboxylic acid formed during biodiesel oxidation can corrode iron surfaces to yield an iron carboxylic salt layer. This salt layer can then trap other components found in the fuel, for example polymers that are also formed during biodiesel oxidation .
Local Fuel Temperature. The influence of temperature on nozzle coking is also significant .The thermal condensation and cracking reaction kinetics of diesel fuel has been shown to accelerate the rate of deposition in the nozzle when temperatures are under 300°C. This value seems to be a critical threshold for coking in diesel engines.
A number of engine design parameters such as EGR and charge air cooling can influence the in-cylinder gas temperature and thus the temperature of components exposed to cylinder gases such as the injector nozzle. These design parameters can also impact nozzle fouling since chemical reaction rates, including those related to injector deposit formation, are very sensitive to temperature.
Injector Geometry. A third factor that affects injector deposit accumulation is the injector geometry. One current tendency in common rail injectors is to increase the number of injection holes (e.g., from six to eight) and to reduce their diameter.This, together with the continuous increase in the injection pressure level, has been one way of coping with Euro 5 emission limits. However, smaller diameter injector holes intensify coking effects, due to their higher sensitivity to fouling. Furthermore, hydro ground and convergent injector holes are often employed as a means of improving the nozzle discharge coefficient and inhibiting cavitation. Unfortunately reduced levels of cavitation can increase the accumulation of deposits in injector nozzle holes. Cavitation in the nozzle holes is commonly believed to help remove coking deposits.
Nozzle Deposits


Nozzle deposits have been a problem for many years .These deposits typically form inside and around nozzle fuel flow holes on the tip of the injector, and can have several important consequences including:
• degrading the injector spray pattern (e.g., reduced jet penetration and increased spray asymmetry) and thus increase particulate emissions,
• deposits on the outer surface of the nozzle can increase the effective surface area for hydrocarbon adsorption or condensation and subsequently lead to higher unburned hydrocarbon emissions. This can give some nozzle deposits a wet appearance .
• a reduction in the effective flow area of the nozzle holes at maximum injector lift and consequently a reduction in the maximum power and/or torque available from the engine.






 

[mcanderson]

Chaps, and I use the masculine purposefully here. This post was about boating on the SoF, not yet another engine/boat/running technique diatribe.

Please feel free to start another post to fulfil that purpose and leave this to about boating on the SoF.

 

[Portofino]

I think we all feel the @€2 / L fuel price and are exploring wether its worth running more D speed in a P boat and keeping it local . In-between the pretty pics .
Of which the SOF is a great place to do that .

If only it was that simple , like a train set just turn down the rheostat / controller and go slower , use less juice .

Weathers gonna be carp wind + rain + cloud along “the strip “ next few days according to forecasts .

 

[Chris H]

I think we all feel the @€2 / L fuel price and are exploring wether its worth running more D speed in a P boat and keeping it local . In-between the pretty pics .
Of which the SOF is a great place to do that .

If only it was that simple , like a train set just turn down the rheostat / controller and go slower , use less juice .

Weathers gonna be carp wind + rain + cloud along “the strip “ next few days according to forecasts .

At least it gives me time to do a few maintenance jobs !

 

[mcanderson]

Rained a bit here last night

 

[mcanderson]

Have used the time to replace the deck shower fittings. Much improved. Only issue was having to enlarge the holes out to 80mm. I hate cutting/sanding GRP. Still itching.

 

[Forty_Two]

Currently 19C at La Napoule & tropical rain. Thing I'll get my electric blanket out for tonight

 

[markc]

Currently 19C at La Napoule & tropical rain. Thing I'll get my electric blanket out for tonight

Yep, it's been grim for the past 2 days, 27 and sunny tomorrow though!

 

[Forty_Two]

Yep, it's been grim for the past 2 days, 27 and sunny tomorrow though!

The great thing is you know normal service will be resumed very soon

 

[jointventureII]

Not SoF granted, I'm in the Maddalena islands at the moment - Santa Maria. It is absolutely howling (at the Mrs' family house, not on a boat). Never seen anything like it, over 50 knots recorded on the anemometer and it's rising. There's a surfable wave in the bay.

Had to move their little boston whaler 17' earlier and just drove it up the beach but it's since gotten even bigger and there is no beach left. August eh!

 

[Bouba]

It’s blustery here as well…that’s Porquerolles on the horizon but I don’t think the photo gives a sense of the wind