Reoccurring Engine Failure / Deisel Problem

[Chewing Gum 17]

Yes Racor is not cheap but you get what you pay for:

[wheels 543]

just remember that a marine diesels use fuel from load not revs

Ummm, no not totaly correct. Not that you are incorrect. It is a factor of both. A bit of a difficult one to be fully accurate with. Remember that first of all, there is a set dose of fuel delivered by each injector in each cylinder in each respective cycle. As the throttle is opened, the rack allows more fuel to be delivered to the injector and hopefully that responds with more revs and if the Revs do increase, then the number of doses per minute is also increasing. So you end up with more fuel more often. It is probabaly truer to say with a Marine engine, Revs determin Hp and Hp comes from Fuel.

Weight has very little to do with fuel use in a Displacement vessel. It affects acceleration, but you can push a 40ft displacement hull along with a 20Hp engine just as fine as you can with a 130Hp engine. The 130Hp will get it there faster. But that is all till you start to get toward the Hull speed. Once you start to approach that end of the Boat speed, the gradiant of Hp required in relation to speed increase starts to go exponential. And as already said above by some, they get very little increase in speed, but some very big increases in fuel consumption. In fact, the normal rule of thumb for Hull speed for a displacement hull is more often than not, incorrect. This is because Hull speed is a mathmaticle equation of a Wave form. 1.5 x the square of the WLL. But we all know that theoretical is not always real world. In fact the more accurate rule of thumb to use is 1.3 x the square of the WLL.

Yes there is a ruff rule of thumb of fuel required per Hp. In fact for most engines, it is pretty close to all being the same. Unlike Petrol. But the very latest High pressure common rail engines are even more efficient again. However, it varies in every boat because there are just so many variables. The type and size of prop can cause the greatest variance by far.

Now one of the big problems with comparison of fuel consumption in Diesels is that not all manufacturers create the numbers equally. You have several different measurements for a start. Just because one engine maker states his Engine is 50Hp for say, is it measured as SAE, SHp, BHp, Continuos, Intermitent and then at what RPM is the Hp been determined at and then add in the torque curve on top of it all. So one makers 50Hp may not be the same as anothers. In fact you can pretty much bet on it adn some can be wildly different. Hence why the Big thumping commercial engines like Cat, Perkins, Cummins and so on, are so flamin big for there published Hp figures. They will produce the rated Hp all day 24/7 for hundreds of thoausands of hrs of life. The smaller high reving things will only produce their max rated Hp for a short time and you will only get 10's of thousands of hrs from them.

[rigger 47]

This is because Hull speed is a mathmaticle equation of a Wave form. 1.5 x the square of the WLL. But we all know that theoretical is not always real world. In fact the more accurate rule of thumb to use is 1.3 x the square of the WLL.

 

Wheels I think it is Square Root, not Square

1.3 x Sqrt(LWL in feet) = knots

 

Square gives a figure that any multihuller (or flyer) would be proud of

[wheels 543]

Thanks Rigger. Now you know why I am not a Nuclear Physicist. I would have split the Atom by lunch time and then have had everything sucked down a Black hole by Home time.

[Guest]

Squid you owe me for suggesting a Tech Talk forum - this is gold and so is Mount Gay - I'll PM you my work address so you can drop it in

 

I'm just pleased I run an outboard (until it gets nasty)

 

EE

[Guest]

Was this your idea?

[rigger 47]

If anyone is thinking of changing where the fuel return line goes, check the manual, check with a diesel engineer.

 

On some engines the excess fuel is used as a coolant for certain parts.

One 'common rail' engine I worked with did this, the feed lines were nice and cool, the return lines were Hot, and the fuel return lines went back to the fuel tank. So if you change where the return line goes you could end up with problems.

Get some advice from someone that really knows the model of engine you have.

[wheels 543]

Sorry if I did not make that point absolutely clear in my previous post.

But also to add, I figure it would be most unlikely that anyone would be installing one of these latest generation engines without all the information, the expertese or an engineer that has that expertese and being a new Engine, most likely the Rep. So my info tends to be more relating to our older and much smaller installs for sailboats.

[rigger 47]

Just thought it worth mentioning and stressing.

These engines have been around for at least 10years in NZ, though they may not have been of the size that we would use in our yachts

[wheels 543]

Wow, 10yrs already. It only seems like yesterday.

 

Interestingly I was looking at a Big Cummins on Sunday with the High pressure system. The Computer said there was a problem and the cause was a low fuel pressure. But the pressure was fine. The Cummins guy said, tighten each injector.

The problem was the injector seats. Over time of heating and cooling, the seat slackens of the tiniest little bit, just enough for the computer to think there is a problem. The engine ran just fine. It was just the computer that said something wasn't right. They each needed a tweek with a big spanner and problem solved. I bet that was an interesting problem to try to solve the first time it popped up for Cummins.

[rigger 47]

A little story about aftermarket parts.

 

a V14 2 stroke

Engine had a top end overhaul, heads off, new valves where needed, new valve collets and so on.

Engine back running and every so often there would be a noise followed by more very expensive noises, a vavlve had dropped.... would replace cylinder head, liner and piston, happened a number of times but never the same cylinder.

 

An engineer that specialised in that type of engine had a look, pulled a head off, dismantled it and found the problem - aftermarket valve collets.

 

All heads removed serviced and the correct Valve collets fitted, we never had another valve drop and make expensive noises

[smithy09 50]

It gets even scarier when you translate the same story into dive gear parts.. Had some flakey stuff come through here with "name"brands on them. Failed one after another.. Pretty bad when it is life support stuff.

[Bimini Babe 0]

Awesome thread folks - most informative I've read here yet. Is this the heralding of a new DR-free era?

 

I have a similar engine in my boat to Fish (1981 Daihatsu CL - out of a Charade I think! Pinnacle of engineering in its day I'm sure...) so I'm paying close attention to all the advice. Will be buying some new diesel additive on my way home, because I too am still using the crusty old bottle that came with my boat! Oops!

[Chewing Gum 17]

We use 4 L/hr with 60hp turbo Yanmar usually doing about 2500rpm and pushing Lidgard 12.6m at about 7-7.5 kts and max 8 knots at about 3200rpm through 3 blade stst feathering Autostream (Aussie prop).

 

Biggest problem we have had is the crap diesel from Westhaven blocking the filters with bug. They deny there is still an issue but I am not so sure.

[rigger 47]

Biggest problem we have had is the crap diesel from Westhaven blocking the filters with bug. They deny there is still an issue but I am not so sure.

 

Have You tried the Gull pumps at Orakei?

[Fish 0]

We fill up using a 20l jerry can filled from the common or garden variaty gas station. Means we don't need to go waste good water time going to a fuel birth (although I'm wasting a lot of good water time fixing the bug problem )

 

The owner reckons last time we measured fuel consumption accurately we were getting 2.6l/hr, but are fairly sure that is before we put the kiwi prop on, which gives us a good extra 0.5knt. 3l/hr is a consistent rule of thumb for trip planning and working out when we need to take another jerry can down to the boat. This is consistent as there is always as much or more fuel onbaord than I've planned for, i.e. never run out.

 

The motor is an Izuzu 3AB1. 3 being 3 cycliders, 1 being the first model ever produced - so super low tech. I'm surprised we don't have two of them, they did come off the ark in pairs

[John B 106]

Apart from the dodgy fuel certainly for all of one year ( 2008/ 2009 season?),the last time I went to that F^%$#* Caltex in Westhaven I chose a very light Northerly day and a leeward pontoon. I stopped the boat bang on about 6 inches off the pontoon and she drifted gently in on the fenders.. all as good as you get.

Only the pontoon has a F%^$#@ big ring around the pole as normal but the F$%#@@ thing projects right out past the side of the pontoon.

When you look at it and the mickey job they've done by trying to wrap rope around it, you see paint of all colours , all over it , including mine.

My marina neighbour came in a couple of days after refueling and that little event with exactly the same dent and my paint in it.

[Fish 0]

Got a price for a new plastic fuel tank.

$560 inc for 69l, same shape as the old one, just shorter, BSP thread to match existing fuel filler. Would need to attach our existing fuel pump / breather fitting.

 

But its only $200 to get a hatch cut in the existing one. Will probably stay with the existing one, just checking it hasn't got any corrosion issues in it.

 

To manage the issue in the future will ensure we use the correct biocide additive. This all kicked off after our usual additive wasn't available and we were sold a duff one by Repco.

 

Will also put the CAV filter at an easily accessable point so we can identify quickly if we have a water issue again and clean the tank out via the new hatch.

 

Have also changed the fuel filler O ring. We can tell if the water was from condensation or rain water around the fuel filler.

[smithy09 50]

Thanks for doing the excersise and keeping us posted Fish. I for one, have learned a lot! I look forward to the final posting saying that you motored all the way to the Barrier without a problem!

[Fish 0]

Got the tank back today with the hatch done. $225 incl GST, also got some cork for making gaskits out of. Some quotes were upward of $400 + GST

 

Hay Smithy 09, when I go to the Barrier it'll be with the kite up and a beer in hand, but if we make it to the Simrad 100 start on time (or at least before KM) I'll be very happy.