Kamd42a one engine using more fuel than other engine

[Restoration man]

Hi all we have got a Sealine 360 statesman with kad42 on shafts one engine uses more fuel than the other ,
On a recent trip to weymouth from souhampton I filled up to the brim at hamble and filled again at weymouth one engine used 35L more fuel than the other engine the trip was done at speeds between 18 and 20 knots stoping for a night at pool on the way ,
Both engines start perfectly and accelerate the same , both sound sweet and nether black smokes and the back of the boat is pretty clean
The only thing I can say is the thirsty engine is down on the revs at flat out speed by about 100/150 rpm , I thought I was imagining it for a while or that it was the eberspatcher that was using the extra fuel but it's been broken all year so it's not that ,oh and the bilges are not full of fuel either ,and the engine oil level is fine as well this is not a recent thing it's been like this for the last 2 seasons ,any advise would be greatly received

 

[rafiki_]

I'm not sure this is so unusual? My stbd engine uses about 10% more fuel than the port one. Reid throttling back slightly on stbd, but no real impact. It heats the calorifier which might draw a bit more energy than port, but once hot, then should cancel out. No smoke or discernible difference in performance between the engines.

 

[omega2]

Those lost revs could be down to fouling of the prop, and the regulator trying to "keep up" by shoving more fuel through but failing, thus wasting fuel, black smoke is produced when there is a lack of air, grey smoke is excess fuel, and blue smoke is burning oil. When were the props last cleaned and balanced??

 

[Momac]

First thing is not to rely on the fuel gauges . They may show full quite a bit before the tank is full.
Secondly I don't know whether you find the fuel delivery pump clicks off or the fuel blows back more so on the port filler than the starboard (or perhaps its the other way around). In any case when the fuel blows back you might think the tank is full but it might not be so .
You could easily get 30 to 50 litres less in one tank than the other.
If you have measured over several fill ups that's fine but I think if you are judging this on one fill up that isn't necessarily conclusive.

 

[Seastoke]

Send Brucek a pm he had same problem

 

[Restoration man]

It's not fouling related I did a flat out run the day it went in the water , I changed the cutless bearings "as they were on there way out "in the spring but that didn't change anything , I've never had the props balanced could that be the problem ? I have no shaking though,

 

[Restoration man]

This is over many full ups ive spent a long time putting the fuel in really slowly to avoid air locks ,I've also tried balancing the gauges and the one goes down faster as well so I'm not imagining it lol

 

[Momac]

If one engine looks to be down on revs at top speed is that because it really is. Can you rule out tachometer error leading you to set one engine at slightly higher revs than the other?

 

[Restoration man]

If one engine looks to be down on revs at top speed is that because it really is. Can you rule out tachometer error leading you to set one engine at slightly higher revs than the other?

Its a flybridge boat and both sets of gauges read the same, it's goto be related because that engine is the one that uses more fuel

 

[A_8]

The props are most likely slightly different. Either some "professional" have fixed them or they are a bit damaged.

I had a similar issue for many years and it was not until I got completely new ones that I realized the prop guy had messed them up, to his defense he was trying to fix some minor damage but at the end of it all they were balanced but not identical as the ones on the other engine.
New props equaled identical rpm's at wot as well as fuel consumption on a pair of KAD 43's.

 

[Restoration man]

The props are most likely slightly different. Either some "professional" have fixed them or they are a bit damaged.

I had a similar issue for many years and it was not until I got completely new ones that I realized the prop guy had messed them up, to his defense he was trying to fix some minor damage but at the end of it all they were balanced but not identical as the ones on the other engine.
New props equaled identical rpm's at wot as well as fuel consumption on a pair of KAD 43's.

It use to rev to max when we first had the boat 6 years ago ,it's only the last 2 seasons it's happened I've not had any work done on the props and both are in perfect condition

 

[A_8]

It use to rev to max when we first had the boat 6 years ago ,it's only the last 2 seasons it's happened I've not had any work done on the props and both are in perfect condition

It could off course be something else but the props may look ok (like mine did) but measure differently. If you've had the boat for six years I am pretty sure something has found its way onto your props and changed their attributes slightly.
Other issues might be the turbo's or the inter cooler clogging up but I don't think that would explain the difference in fuel.

 

[Momac]

What else can you rule out - filters , belts ? Is temperature equal and okay on both engines ? Any engine oil consumption? Any engine oil leaks ?

 

[NormanB]

Is the fuel injection rail leak off going back to one tank?

 

[Restoration man]

What else can you rule out - filters , belts ? Is temperature equal and okay on both engines ? Any engine oil consumption? Any engine oil leaks ?


I don't think it's filter related ,I did have a mild bug problem but sorted that out last year ,now I'm a bit obsessed with changing the filters and checking the water separator "separ filters" after every trip I take a sample ,both temps are the same and oil preasure is perfect and hardly any oil leaks at all
The engines were fully rebuilt by mike wills just before we bought the boat infact when we decided to buy her the engines were out of the boat, they have only done 400 hours in 6 years and have never let me down once and run like clockwork

 

[omega2]

In that case stop worrying and enjoy, I doubt any twin engined boat has equal consumption of fuel, lots of variants but most port engines suffer while the starboard one goes on forever. Another way to put your mind at rest is to link both tanks, then they will go down together, but will also run dry at the same time. LOL

 

[Momac]

hardly any oil leaks

Running out of ideas . ................ Where is the 'hardly any oil' leaking? ................On the floor / under the intercooler perhaps?

.

 

[Seastoke]

Look at it like this you might be saving 35 l on one engine

 

[Restoration man]

Running out of ideas . ................ Where is the 'hardly any oil' leaking? ................On the floor / under the intercooler perhaps?

.

Your right!! the only bit of an oil leak is off the intetcoolers they both look like they weep a bit , I read. Something on this forum a while ago but I came to the concision that they all do it a bit and it was nothing to worry about ? It doest actually drip much oil on floor as such more of just a weep, this is on both sides ,the intetcoolers are very hard to get to on this boat

 

[Restoration man]

In that case stop worrying and enjoy, I doubt any twin engined boat has equal consumption of fuel, lots of variants but most port engines suffer while the starboard one goes on forever. Another way to put your mind at rest is to link both tanks, then they will go down together, but will also run dry at the same time. LOL

You saying that about linking both tanks has put an idea in my head I could try and swop the fuel taps over so everything draws off the good engines tank ,it might eliminate the pick up in the tank on the bad side ?