Flat out or not flat out?

[Guest]

We are told that most marine engines are bassed on comercial units. with this being the case why is the rev counter in the cab of a truck marked with an optimum usage range far lower down the rev band than we are advised to run our marine versions? I've heard the bit about better cooling but I can't believe that every truck operator in the country is paying for a bigger power unit than he would need if he used the engine to its full potential if this was th case larger radiators would have appeared long ago. Or is this a way of ensuring thoes big repair bills arrive on our doorsteps every year. Does leisure use mean "you can thrash the nuts off it but only twice a week"? If a 400HP Merc truck (excluding oil change)only needs a major service every 1,000,000Km why does a marine engine need it every year approx 200-500 hours? comments invited.

 

[Guest]

Sounds like a trade excuse based on unproovable theory.

 

[Guest]

Firstly, Chris, I'm not in the 'trade' and, secondly, you only have to look at engine manufacturers' literature (yes, I know it's sad) to see the wide range of power outputs available from the same basic engine. Truck operators trade power for economy, reliability and extended service intervals. We boat owners want to zap around at 30 knots whilst carrying enough gear on the boat to be self sufficient for a year so we trade serviceability for power

 

[Guest]

Chris, Mike is right on this. If you want the ultimate example, look at F1 racing where the engine is rebuilt after each event. We once tested a Sunseeker back in the 1980s that had race-tuned engines...the owner knew he would be in for a rebuild inside of 500 hours but I doubt the boat ever logged that much in his lifetime. The other problem, ironically, is with the use that engines don't get in boats. Imagine that when you leave your craft, at least a cylinder or two is directly exposed to the elements via open exhaust ports. I'd much rather buy a boat with high hours than one that had been sat unused all season, but low hour boats are often sold like low-miler cars. Ho-hum!

 

[Guest]

Re: clutches + gears?

Yes, agreed with Mike + Kim's..and gearing, a truck will exert a (heavy) load at 2000 rpm. It also has a clutch, so can raise revs and dump the clutch.

By contrast, the same engine in a powerboat has no clutch, and only a single gear. Reaching 2000 revs always follows a gradual application of the power, and always against a gentle and (effectively decreasing) load as the boat speeds up.

So, notwithstanding m'learned friends above, I'd say that rev limits in trucks are due in part from some consideration of the ability of power train to take a rapidly/suddenly applied load. Higher limits in boats recognise the gentle application of power hence higher limits.

 

[Guest]

You've partially answered your own question, Chris. Whilst marine engines are often based on the same blocks as engines that power trucks and, indeed, construction machines, the operating duty is very different. Trucks/construction machines typically operate for maybe 3000hrs a year under varying load conditions and, in order to achieve this, engines for this type of duty are significantly downrated on power and often also have very different torque characteristics. Leisure boat engines on the other hand, operate for maybe 100hrs a year and generally under constant load and, because (theoretically) this is a much less onerous duty, engines for leisure boat use can have a much higher power rating. Also, because leisure boats are generally getting heavier thanks to the ever increasing level of must-have domestic equipment being fitted and because buyers of leisure boats, particularly planing ones, are generally obsessed with top speed, engine manufacturers are locked into a continuous race to produce yet more power from yet lighter engines. So, whilst these engines are designed for a once a week thrash the nuts off 'em jaunt across the bay, users have to recognise they are becoming very highly tuned units and require regular and costly maintenance as a result.

 

[Guest]

Hi Kim long time no chat. Ignoring MattS's obvious lack of knowledge with regard to modern truck power management. My point is this. There is no specific definition of "leisure use". It's a shame you use the example of a race engine, I think it was Colin Chapman that said "if the car does an extra lap it's been over engineered". How long is your race? How many boat builders ask what use you will put the vessel to and fully explain the limitations of the engines and equipment specified. How many of them know the answers? At the next boat show ask around the stands and find out which of the engine manufacturers can tell you if their power rating is all day or only for 1 hour. You won't need a large post card to record the answers. Trying to get an engine output power and emmission mapping is totally impossible even if it's prommised on the day your enquiry will get "lost". This information should be part of the Technical Construction File that all manufacturers have to have by law to sell in the European market. How long will it be before a claim is rejected because the boat was used for longer than the manufacturers idea of "leasure use"? Remember the trouble you had with Volvo over a dropped valve, what chance does a private individual have? If the full operating criterior were made public the dreaded re-engine and certification would become a simple paperwork exercise instead of the great black hole that numerous misinformed threads on this site make it out to be. I know that you and I have corresponded on this subject in the past and I presume that in your new role (by the way congratulations)you won't have the input to the mag. But if you see the new guy in the lift, propper Engine performance documentation and compliance with the CE requirements would make life for the boater a lot easier and would be a worthwile cause for the mag to take up.

Best regards

Chris P

 

[Guest]

Chris, I'm not that far away and I will be staying in touch. Plus we'll be keeping a much closer eye on motorboating matters with ybw.com, mby.com and motorboatsmonthly.co.uk through this year.

You are right that all sorts of measures (horsepower, duty cycle etc) vary from manufacturer to manufacturer but they often do in the non-marine world too.

The problem with the Volvo Penta KAD44 that we highlighted in gory detail a year or so back was due to incorrect servicing of the engines (no valve adjustment), not engine hours or duty cycle. Rather than let this thread wander off onto another subject, as so often happens, it is more relevant perhaps to highlight the fact that taking a cylinder head off did give us the chance to observe that Missing Link's cylinder bores were in great shape after 600 hours or so over just a few months. I ponder what an equivalent age boat with only 20-50 hours would have looked like should one have the unfortunate need to reveal the engine's innards.

I say nothing of this as a defence of anyone, but whether we like it or not the drive for better and better power to weight ratio for diesels has taken us, if not into Colin Chapman territory, then at least into areas where leisureboaters are more out on their own.

Going back to our KAD44s, the reason we got to the point where the valve dropped before anyone else had discovered the potential for failure, given no adjustment, was because there is no commercial version for that rating of the 40-series block and Missing Link had probably logged more hours than any other craft with that engine for the given period of time, Volvo's Swedish test fleet excluded. No doubt the valves get checked in Gothenberg as indeed, hopefully, they are now in the UK, even if it is the mother of all jobs to do.

I've always worked the Volvo Penta 30 and 40-series diesels that I ran for the last 11 years on a one hour in 12 flat out, 200rpm down from maximum for the balance basis. I'm sure I found that detail in literature but would have also talked to various dealers and VP UK about the subject. Admittedly it wasn't hard to do that on my steel displacement boats but with the two Sealines it was best to keep a sense of perspective, esp when flying around chasing other craft (and the sun) on photoshoots where the last thing on my mind was the position of the needles on the tachos.

In my job as MBM editor I was all too aware of the faults that have arisen over the years with all typical makes of diesel fitted to motorboats, but I was also often bent treble-jointed into some boat or other cursing poor access (a major reason for failure) or poor maintenance (if ever there was an excuse for my habit to dress down, the number of times I have emerged from other peoples' bilges looking like a coal miner on double-shift was it). Both of these don't much help reliability either, something I regularly used to bang on about in MBM.

Thanks for giving me an excuse to keep my throttle hand in but I'm going to stop there...the coffee has run out!

 

[Guest]

Chris, I guess 'leisure rating' for marine engines is defined by some EC directive but you have a good point in that what happens to your warranty if you use your boat outside the definition. For example, what happens if you fit leisure rated engines to a boat and then circumnavigate the globe in, say, a year? Would this invalidate your warranty?

Can't agree with you on lack of information though. All the major engine manufacturers have literature and websites which give you all the information you could ever want on power curves, emmission data, consumption data, dimensions etc. Of course, if you want information on an engine which went out of production years ago, that might be more difficult

 

[Guest]

Kim, congratulations on your 'elevation'. I wish I had the kind of employers who'd let me bugger off from the office to sail round the UK and then give me a promotion when I got back!

 

[Guest]

Mike, so you've not heard the theory about why people get promoted up yet then!

It's also the only way they've found to keep me at my desk for three long months. Your reminder of the Round Britain is apt as I haven't spent so long huddled over a glowing screen well into the night since those fondly remembered days.

That said I've just found a reason to escape onto the water this Thursday; can smell the salt air already. And looking forward to turning up on an event or two this summer as a happy punter (as if)!

 

[Guest]

Ta Chris, have your contact details in my big red book. Mind you, seem to remember a red-eyed guy trying to make some sense of a big event somewhere not too far away from my office?!

 

[Guest]

Mike, interesting thing is that all electronically-managed diesels now capture certain info on their built-in ROMs. So of you cook them or thrash them, someone can check. The flip side is that it can also prove you didn't do those things, so as long as you are responsible and honest then big brother might work in your favour. If you suck a bag up over your outdrive, overheat, blow the engine and want to blame someone else, you are in trouble...unless choosing to fight out why the overheat alarm didn't go off first.

It is also possible to interface instruments or a PC to some of these engines. What I like about it is you get greater accuracy than from analogue instruments that suffer from the usual rash of voltage drop-induced errors.

Just fitted electronic gauges on Calm Voyager's KAD44s and was looking forward to getting good data when I handed her over, although the MBM guys will be doing that soon anyway. Oh yes, and I willbe trialling them on Thursday. Well, got to keep my hand in.

 

[Guest]

The only problem with electronically controlled diesels is the electronics. Spent a delightful Sunday afternoon last season effing and blinding at a pair of KAD44's, one of which refused to start thanks, as we found out later, to a certain Sealine salesman having switched off the ignition with the gear lever in reverse. Had the engine been mechanically controlled, of course, even somebody like me might have noticed it from the gear lever position but the only clue was the mournful flashing of a little yellow diagnostic light on the dashboard which according to the Volvo handbook was telling me the oil pressure was too low! Eventually fixed by a very nice Sea Start man with a lump hammer judiciously applied to the nether regions of the recalcitrant engine. I think it's what they call progress

 

[Guest]

Don't start me off on KAD44 start techniques. Already learning never work with children, animals, boats or technology...

 

[Guest]

Kim If ever you need a reference about how hard you work on your trips give me a shout

Chris P

 

[Guest]

Re: oh, sorry, an MBM lorry driver

...old enough to quote long-dead engineers, of sorts. Let's all post a message, then slag any contributors.

What's the difference between a powerboat and a truck? Well see, a truck is where you belong, and a big expensive powerboat, see, ...isn't. Back to your Volvo's, replacement engines an'all?

Guarantees? They're the things that people who buy the low-quality gear for less money hope will compensate for their willingness to risk spending less. Then they complain about the wording.

Expensive things are good, cheaper things usually aren't. Easy innit?

You need a cheque book and £150k for a boat, 10% per year. Or, £300k +10% and then it'll be in MBY not MBM.

 

[Guest]

Re: oh, sorry, an MBM lorry driver

Been an engineer for over 25 years desigining equipment that makes your 300K look like a single item on my spares list. Dont knock the lorry driver he has to carry every thing that you use and still has to put up with the likes of you trying to commit suicide under his wheels. I have no problem with responses from informed sources but from previous strings you seem to have an opinion on everything and knowledge of nothing.

 

[Guest]

Re: Whoa we got one ...

Ooh, ChrisP. I know plenty! Or should we bow to your superior knowledge on all matters? Here's one thing I might know about...

Tip to get promoted! 1. Adopt a positive attitude. Nobody wants every posting to be a whinge about guarantees, flat batteries that you managed to discharge by leaving the fridge on weeks and so on. I imagaine that you're the same at work. 2. Think about how other people might actually not be doing the same thing for 25 years. 3. Consider refraining from regular net use at work first thing and some lunchtimes every weekday before the boss arrives.

hm?

 

[Guest]

Re: Whoa we got one ...

Don't ever try to make a living as a psycologiist, it's yet another subject you know nothing about, you'll starve. Rember this, pissing contest and smart remarks are for small boys and insecure adults. Enjoy yourself because nobody else will.