Volvo Penta KAD42 Low rev and speed problem

Tiam1838

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Hi, I have a 1991 Fairline Brava 33, 35ft hull number FLN-GB0938J191 running on Volvo Penta KAD42 twin engine. I am facing a rev and speed problem running on 7-8knot on full throttle.

i saw on an old thread that an existing member had the same problem and adjusting the fuel and air timing fixed the problem.

can anyone with the expertise advise where and how do I adjust the fuel and air timing for these engines? Thanks
 

alldodge

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Just re-read thru the old thread and as you noticed he never came back to confirm. The guy saying that it was fixed in 10 minutes and he was off and running lead me to think then as now, there was something simple that we went over that was not done.

Never hear of then nor now of Air Timing. The KAD42 is a good motor but has a lot going on with a supper and turbo charger.

Sounds like your having trouble with both motors??
What are the visual symptoms, black smoke, white smoke?
One motor has more rpm then the other?
 

Tiam1838

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Hi Alldodge,

thanks for for the reply.

both engines are running on same rpm and when it’s on full throttle black smoke is presented.
 

alldodge

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Black smoke is not enough air. If only one was smoking I would normally think the turbo but both maybe control.

It could still be on side and not both even though both are producing black smoke. Another thread discussing TAMD74's had same issue, and after many tires it turned out to be the turbo needed to be replaced. The supper charger helps until the rpm's come up then the turbo takes over, but the turbo was not building enough pressure

http://formulaboatsforum.com/VBFORUM/showthread.php?7155-turbo-chargers&highlight=divergirl

Another issue which can cause the issue is if the exhaust gets clogged due to things like the muffler collapsing inside, air filters

Do you hear the turbo whistle?
 

Tiam1838

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Hi,

if if it’s not enough air can advise how this can be calibrated? When the engine is not started yet, I can rotate the turbo fin using my hand and when the engine is started, the turbo fin rotated without any whistling sound.
 

alldodge

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There is no calibration for air, the vanes get spun by exhaust gases and the other side pumps fresh air into the intake. A boost gauge can be installed in the intake side to determine if turbo is spinning high enough to pump air in at sufficient quantity
 

alldodge

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The thing with a diesel, is so long as there is enough air, the more fuel which is introduced, the more power. If not enough air is pumped in, the more fuel only reduces power
 

QBhoy

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Hi

spinds like you might be over here in the U.K...going by the fairline boat. One of the best !
anyway. As you might be aware...all the KAD series engines are supercharged and turbo charged. They rely on the supercharged to get them up to revs capable of producing enough exhaust gas to spin the turbo.
I would be looking at the supercharged belts and clutch. Might seem unlikely on both engines...but you say there is black smoke...which suggests it’s getting fuel and that’s not the problem.
Normally when both engines have bother...it is fuel related. Check for water in the pre filters anyway.
Between the two suggestions, it will likely be one of them.
 

Tiam1838

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Hi QBhoy,

im here on sunny Singapore, thanks and sorry for the late reply. Both the supercharged and prefilter were fine. I had a new prefilter changed so most probably something with the turbo, now got a mechanic checking on the turbo. Hope will be able to resolve the problem soon!
 

QBhoy

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Yeah me too...still suspecting supercharger engagement or lack of it, but if it’s both engines it makes it maybe unlikely. The only commmon thing to them both is fuel.
Unless you have a barnacle colony living on your hull....haha.
 
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