UNBURNT FUEL DIESEL

[Doverescape]

Good Day to you all or evening depending on time zones.

I have a Sealine S23 (British boat) with a Volvo Penta KAD32 DP Duo Props.
According to the manual max RPM should be 3900 and top speed around 30 knots
As you can see when I pull away at WOT I get the following residue left in the wake.
It has always had problems and I have recently had an air leak identified from supercharger to turbo and in fairness have not really had a chance to give it a good thrashing (Chinese service) since so am not sure if I have a huge build up of unburnt diesel that will take a while to clear but am doubtful.

I have been getting a max speed of about 22knots and only when the water is as flat as a Witches *** and a max RPM of around 3200
List of what I already done.
New props (A4'S)
Injectors overhauled
New fuel and air filters
New speed sensor
Turbo overhauled
Clean bottom etc
Tappet clearances checked and good at 0.40mm
Intercooler cleaned
Throttle linkage checked to see that I am getting full throttle.

Not had compression tested but it starts on the button and ticks over very well so pretty sure they are ok.

I am pretty sure that I have come a bit obsessed with this but feel that there is something that is just not quite right. It used to struggle to get one the plane prior to air leak but now pops up like a cork.

As you can see from the pictures I would probably get arrested for water pollution if anyone saw this so I am wondering if anyone can offer me any light inspiration.

Regards

Steve

 

[alldodge]

That doesn't look like diesel it looks like oil. Diesel is kind of clear unless that also includes carbon from the exhaust.

The motor has a smoke limiter which limits the length of stroke of the injection pump until the turbo has time to build pressure. If this is not working correctly it would allow to much fuel during throttle up from idle and would belch smoke and could put more fuel then it can burn.

Your not reaching WOT rpm which could mean many things but the smoke limiter would not be the cause. Not reach max rpm can be caused by build up on the prop or hull (prop and hull has been cleaned). Low compression will also reduce the power need to achieve max rpm's but could still run fine.

Does the motor smoke at any other time?

 

[Doverescape]

Thanks for your reply and only a bit of black smoke on start up then it pretty much clears

 

[alldodge]

No smoke when throttling up to get on plane?

 

[Doverescape]

No no smoke when trying to get on the plane

 

[Doverescape]

No no smoke when trying to get on the plane

Hull was stripped back to fibreglass and had a number of coats of antifoul as did the leg and trims so that was sadly not the issue
Thanks
Steve

 

[alldodge]

Assuming, oil level is good and doesn't change.
If a diesel gets more fuel then it can burn it can come out as white smoke. Might not notice white with exhaust in the water

Also assuming the turbo to super charger leak was fixed

I would consider a compression test.

 

[Doverescape]

Yes it's about the only thing that has not been done, just that and the fuel pump which I believe is not a D I Y job ?
Thanks
Steve

 

[alldodge]

Compression and injection pump is DIY, but does take some special tools. Compression is much higher pressures, so the fuel injectors are removed and test fitting is inserted in its place.

Injection pump is easy enough to remove and reinstall but just need to set timing on motor and pump before reinstall. Most use a bolt on the flywheel for the block and a pin into the pump. Then the pump is installed and pins removed.

Might be worth it to see what it would cost for a tech. Main issue with a tech is finding one that knows their stuff. There are folks on the Formula form which have spent a fortune trying to find a VP tech that actually knows the motor

 

[Doverescape]

Agreed
I think that as I have had the air leak for probably a very long time that I probably need to give it a half decent run to see if it clears.
I read the old manual cover to cover last night and there are hardly and service items that I have not done yet. I did pick up on the fuel filter change and not sure that I ever primed the pump manually after fitting but surely it would not be starting as well as it does or ticking over or could I be mistaken and have made a schoolboy error ?

 

[alldodge]

Replacing the fuel filter and not priming the filter and bleeding air normally causes the motor to stall in short order. Afterwards, it needs to be bleed to get it to start again. Your motors running so that's not the issue

As before, if you check the motor oil level and its not changing from one run to the next then its not motor oil or blowby

An air leak will cause a loss in power

 

[QBhoy]

Hi. I’m now quite familiar with this wee engine. And as it happens, with this very boat. Although it’s the s25. Same hull though.
Firstly I’ll say that the performance on these particular boats is hugely affected by trim on outdrive and also trim tabs. Usually you’ll use the tabs down and outdrive trim down, to plane quicker but very worthwhile saying that if you don’t lift them again, you’ll lose so much rpm and speed on these.
I think that’s maybe where you’re losing rpm and speed from perhaps.
As for the black stuff in the water. I’d say that unless you have serious serious issues, that’s not from the exhaust. Is there any chance that it could be from the automatic bilge pump coming on or elsewhere?
If I’m wrong...then check your supercharger is clutching in and out as it should.

 

[QBhoy]

Assuming, oil level is good and doesn't change.
If a diesel gets more fuel then it can burn it can come out as white smoke. Might not notice white with exhaust in the water

Also assuming the turbo to super charger leak was fixed

I would consider a compression test.

All dodge. It would be black smoke if it is getting more fuel than it can burn, usually. Or not enough air.

 

[QBhoy]

Hi. Just in addition...make sure you’ve changed that supercharger oil too. Only takes less than about half a litre and so easy to do.
But I’m really keen to hear if you’re lifting the trim tabs and outdrive trim at wot.
also like to hear if you definitely hear the supercharger engaging around 1000-1200 rpm, then cutting out around 1000 rpm later when the turbo can take over ?
I’d also say that you have the most fiercely pitched props these came with standard. But I know that some guys with these have in fact went down to A3’s or the modern equivalent. I’d rather the A4’s though. The boat I’m familiar with has a4s. She will do around 36 mph easily.

 

[alldodge]

All dodge. It would be black smoke if it is getting more fuel than it can burn, usually. Or not enough air.

Oh all knowing wizard of everything, not necessarily, think about it for a bit longer

 

[QBhoy]

Oh all knowing wizard of everything, not necessarily, think about it for a bit longer

Not at all suggesting I am AD. Like to think myself quite humble on here and ask for help on things as much as I perhaps try to give out.
But one thing I’m certainly confident about, is Diesel engines. It’s my trade.
I presume you are referring to the extreme case of completely raw and unburnt diesel fuel being thrown out the exhaust and giving off white or hazey mist (not so much smoke) ? But in this case, it wouldn’t happen. 100%

 

[QBhoy]

Oh all knowing wizard of everything, not necessarily, think about it for a bit longer

Not at all suggesting I am AD. Like to think myself quite humble on here and ask for help on things as much as I perhaps try to give out.
But one thing I’m certainly confident about, is Diesel engines. It’s my trade.
I presume you are referring to the extreme case of completely raw and unburnt diesel fuel being thrown out the exhaust and giving off white smoke ? But in this case, it wouldn’t happen. 100

Oh all knowing wizard of everything, not necessarily, think about it for a bit longer

its certainly unusual i don’t agree with you AD and always love learning from you, no doubt.
but honestly, pretty sure with this it’s not a leaking injector and throwing raw fuel haze out. You’d notice the rainbows and fuel in the water as a result.
When these things are not breathing correctly and too much fuel to burn...always a ton of black reek from them AD.
I’m not sure I’ve mentioned much about working on these things on here, mainly because you guys are all mainly North American and more perhaps along the lines of petrol motors.
For the last 17 years We’ve had a princess 40ft boat with twin Tamd61a Volvo Penta diesels. I’ve looked after these over the years. Getting a handful now, as I get less flexible to reach water pumps, inter cooler drains and oil filters, haha.
When I was still in school, I was sponsored by a shipping company called Stena. They allowed me to finish off school, then gave me a wage to get an engineering diploma for 3 years. After that I passed a written and oral panel with the MCA to then become qualified to go to sea as a marine engineer. Worked up from junior engineer to first engineer and running the engine room. Class 2 combined steam and motor unlimited.
Diesels were always my thing really. Just haven’t said much around it on here...perhaps for the worry of boring you guys. Since then, I’ve been learning as much as I can about smaller GM petrols I now love in my boats. Learning from guys like yourself ! Always appreciated

 

[alldodge]

Diesel is trying to start, but nothing but white smoke, reason?
Unburnt fuel exiting

Diesel is running but says its low on power (unable to reach WOT as before) and lots of fuel is pushed into cylinders during take off, what might be seen?
If one cylinder is low on compression then the extra fuel will not burn and can extinguish the fuel that was going to burn

No expert, but have also gone to diesel school. Your better then I for sure, just an old guy talking about things I've seen over the years

 

[QBhoy]

Diesel is trying to start, but nothing but white smoke, reason?
Unburnt fuel exiting

Diesel is running but says its low on power (unable to reach WOT as before) and lots of fuel is pushed into cylinders during take off, what might be seen?
If one cylinder is low on compression then the extra fuel will not burn and can extinguish the fuel that was going to burn

No expert, but have also gone to diesel school. Your better then I for sure, just an old guy talking about things I've seen over the years

Fair play AD. I get what you’re saying and your reasoning...but with these particular wee things, along with their larger siblings..it’s not really a thing for them to blow fuel mist out the back in the water.
With a leaking injector on these things, the most you’d know is a cloudy diesel rainbow effect in the water at idle at the dock, especially given away, if it happens when up to temp, as you’ll know as well as I.
These Kad32 are an evolution of the old faithful ad31/tamd31 4 cylinder VP’s that have been around for decades. Trade mark is to smoke on start up until warm...have sound as rough as a bay of spanners if not well insulated, love to be worked hard with their old school mechanical injection system feeding them....but most of all, suffer from huge turbo lag when trying to get out the hole...it’s like nothing, nothing, nothing, lots of black smoke...then the start of a whistle...spool of the turbo coming on boost and away they go and eventually getting the fuel air mixture at a less offensive level.
So fast forward a few decades to the late 90’s and early 2000’s...VP throw a clutched supercharger on the front of the 31, to stop the horrendous turbo lag and sooty over fuelling issue and call it a kad32. This means the wee thing acts more keenly down low and can run fairly keen pitched duo props like A4’s on these. Doesn’t have to wait for the turbo to come on song. When the boost is there for the turbo, the SC retires. All stuff you’ll know, no doubt. But thought I’d mention anyway.
Id think this issue is to do with either trim and trim tabs, the engine not being worked hard enough and suiting up and/or a previous or current issue with compressor or turbo. Most likely the common issue around the exhaust elbow from turbo failure. They can fail horribly here and decorate your engine bay in black suit.
Anyway. Keen to hear how the fella gets on.