Diesel engine expert- Engine diagnosis required please...?

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Nickcf

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Ok, 2 x VP TAMD 74p diesels (2002) with EDC- no visible smoke when underway but depositing moderate amount of soot over the transom (Princess45) which needs to be cleaned off after every trip over two hours (which is getting very boring...). This has developed over the last couple of years as used to burn very cleanly. I know the Princess design creates some backdraught which sucks the exhaust back over the transom but I'm assuming that there is now some unburnt fuel in the exhaust which causes the soot.

All the filters have been changed (air, oil, fuel etc) and engines run very well and can get the P45 up to 30+knots without a problem. Fuel consumption hasn't really changed (about 1mpg at normal cruising speed). Don't know if one or both engines are causing the soot as no visible smoke when running.

My thoughts are could be one or more faulty injectors, turbo not running efficiently, poor fuel (although seems to be similar from all vendors used in recent months) or something else..?

Can anyone advise what are the best tests to carry out to try to pinpoint the cause?

thanks

Nick
 
Just had this same problem same engines in phantom 46 2001 year, tested and set injectors, changed filters did some edc diagnosis and sea trials tests on boost etc, changed some edc sensors and cleaned some sensors etc, if your southcoast I can have a look.
 
I also have a Princess 45 Flybridge (2002) which I've owned from new and have exactly the same issue; mines's been fully serviced and fettled like you wouldn't believe. I've been told that this is normal (a light greyish deposit over the rear of the bathing platform) and I've checked this out and this seems to be the case.
I don't think there's enything wrong with your engines (unless it really is a black deposit), but I have found that using an additive (I've used Fuel Set) does help but doesn't eliminate things completely.
 
Hi Norbert,

Thanks for response; yes it is more a light grey deposit and does wash off fairly easily so long as the grp has been well polished previously. Does it get onto the back of the plexiglass screen under the radar arch on your boat?

I may try some fuel additive next season.

Nick
 
Sounds very normal, diesels produce a lot of carbon particulates under normal conditions and it will tend to stick onto the transom.

An issue with most power boats is that the engines need to produce maximum power or torque or more often both, to get the boat on the plane. Inder these conditions the engine is at the ragged edge of flat out and engine manufacturers tend to overfuel at that end of the envelope to ensure the engine meets its output spec. Unless there are other basic things wrong (not so in this case) like blocked air filters or poor quality fuel then I would leave well alone.

Road grade diesel may improve matters because rumour has it it burns cleaner but its an expensive experiment to perform, I would stick with red and fuel set and a squirt of washing up liquid!
 
I seem to remember that one of the reasons 74s were 'upgraded' to 75s was to reduce a renowned black smoke problem and improve fuel efficiency. Probably find more meat on that in the blurb on the 75
 
Hi Nickcf - apologies for the delay in responding; yes, I have seen some on the plexiglass panel at the rear of the flybridge and, like you say, it washes off fairly easilly. I really wouldn't worry - a guy moored near me was in the trucking business and knows all about fuels, etc and - like Marsupial says - the diesel that we are getting is not just road fuel with the red dye added, it really is c**p (according to him). if you look at many of the boats that have 74P installations; you tend to see the same problem of crud over the back..
 
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