Advice regarding noise, power loss, overheat. KAD engine

BruceK

BruceK

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KAD 42

Background- may be related
A few weeks ago on a cruise port engine outdrive lost it's rear prop. Were C4's.

C4's not immediately available replaced all 4 props with equivalent B5's

Continued on cruise all is fine maybe a slight decrease in revs for cruising speed from 3200 to 3050 for same speed.

Filled up with fuel from a new marina / source

Got onto plane effortlessly and performed well. I was delighted.

First instance
Coming back to home port cruising in hot ambient temps engines running 5C hotter.
Got onto plane easily enough and covered 15 mile before I thought a small single engined aeroplane was buzzing me. That was the noise. Small single engined prop tip buzz/boom. Not quite like a helicopter but there.

Engines went to 100.

Let the engines cool while at displacement speed and engine sounded just fine.

Boat struggled to get back on the plane (single engine aircraft prop noise gone and subsequently never returned. Was it my imagination? I heard it quite clearly but no one else seemed to) with supercharger bouncing in and out unless on kick down. It's the Starboard engine i.e. not the one that I lost the prop on originally. Symptoms have remained on subsequent 2 trips out. Engine now runs hot. Just shy of 100C. No loss in max rpm functionality. Engines will rev to ~3700rpm and sound good. Just a complete gutless midrange and quick over temp struggling to get off supercharger

More unusual behavior. In neutral I can rev the starboard engine to max rpm. However when coming off the throttles slowly, when the engine reaches ~2600rpm and the super charger kicks in (reverse sequence here) the revs immediately drop to ~2200 rpm as if the super charger is tight and loading the engine. It is not though. It can be easily and freely turned by hand.

I will be replacing exhaust elbow and thermostats this weekend to see if that cures the temp issue. Raw water pump is new and good changed this winter and cooling system was decalc-ed chemically with Rydlyme and will checking turbo for wear. What else could cause these symptoms and a loss of power in the mid range? I'm leaning towards turbo, but the symptoms came on awfully quickly to be turbo wear, I think.
 
first thing is sort the over heating - change the impeller - the core may have spun out so will look OK but not be very good, blockages in pick up pipe, carp in the leg opening - what is the water flow like in the raw water filter?
I don't think your cooling system is completely clear - its pretty hot in the UK at the moment but what is the sea temp? I'm in the med with kamd 300s with seawater at 30 degrees and I'm seeing @ 84 degs at 3300rpm
get an infra red handheld thermometer and start measuring temps on both engines - thermostat housing, cylinder head, heat ex-changer inlet and outlet pipes, exhaust elbow near where the cooling water goes in, see what differences you get.
Take the exhaust elbow off and have a good look inside and check the stainless insert at the turbo end for pin holes.

second thing midrange grunt- don't think it's the turbo as you can get max revs under load. don't think its fuel blockage for the same reason. If turbo was knackered you wouldn't get max revs and you would get the hunting on and off the supercharger behaviour. The lack of mid-range grunt sounds like a supercharger issue. Is the clutch on its way out and slipping? Or is the clutch coil going with a bad contact developing internally? I'm thinking electrical problem with supercharger as its just started out of nowhere. Turbos fade away.
Get someone else to drive and watch the supercharger clutch as it engages and disengages - look for sparks. is it intermittently stopping and starting?
try disconnecting the electrical supply to the supercharger and see if it gets worse or stays the same. (don't think KAD 42 ECU will notice). If you have a multimeter measure the resistance of the clutch coil - I think it should be about 4 to 5 ohms
 
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Thanks Kashurst. Definitely not the supercharger. The problems start after the supercharger kicks out. Sudden and huge loss of grunt and port engine has to take up the slack to pull it up to speed. It's a sports cruiser, you can clearly hear if there is any clutch / slippage issues and the harmonics from both engines when on supercharger are the same.

Once off the supercharger (unless in kick down mode) the port engine will slowly climb to 3000rpm while the starboard lags at the supercharger cut off / hunt area of 2500 / 2600 rpm and eventually when the boat reaches about 17knts will suddenly climb to match the port engine at 3200 cruise speed.

However when in kickdown mode both engines will quickly climb to 3000 rpm but no further. You actually have to back off the throttle from kick down mode to disengage the superchargers and then suddenly the revs will climb to 3200 cruising revs or higher. It's very bizarre. I have had a look at the non return flap in the Y junction of the airbox and it is free and loose. No stiffness at all so it cant be that either.

edit

although what is noticeable is you dont hear that back pressure whumph! noise when you come off the turbos and hear it bang closed any more either
 
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from what you describe, that sounds more turbo or fuel related. Are you getting any black or blue smoke?
just a little thing to check - if you have racor fuel filters, take the bowl and spinner out and remove the little silver ball and the red seal. It's an anti-run back device that doesn't actually work very well, however if there's any crap in there, the ball can block the fuel flow in an erratic way. (top tip from local Volvo dealer)
after that its probably boost pressure checking time.
 
Will do. You suspect air leakage tear? I have yet to take it off to check but when checking the non return flap did not notice anything amiss while removing the Y piece and the clamps are all on tight. Might account for the aeroplane prop noise I was hearing when the problem started if air was blowing threw a rubber tear. Good point. Thanks
 
from what you describe, that sounds more turbo or fuel related. Are you getting any black or blue smoke?
just a little thing to check - if you have racor fuel filters, take the bowl and spinner out and remove the little silver ball and the red seal. It's an anti-run back device that doesn't actually work very well, however if there's any crap in there, the ball can block the fuel flow in an erratic way. (top tip from local Volvo dealer)
after that its probably boost pressure checking time.
 
I'll check the Racors. Thanks. I have been remiss. I have not changed the filters there either as the fuel bowl is clear and there is no crud in it. I did as mentioned in my first post fill up from a new source just before this happened. Early season. It's a stretch but a possibility the fuel wasn't up to scratch.
 
I have no reliable way of checking boost pressure where I am. Was not something included with KAD42A's and the engineers here are diabolical. If I suspect the turbo I will rather send it off to be checked by a specialist and repaired / replaced if necessary. I was surprised that you can get these original Borg Warner units at a fraction of the Volvo price and it's the same thing. Cost less than filling up the tanks. Not worth the effort to bring an engineer out from "out of town" to check boost. But as you say, the onset seemed a bit sudden.
 
if you get to the point where you are 90% sure its turbos, just buy new ones, usually the exhaust housing corrodes away and the gap around the impeller gets too big. no doubt someone else will be along soon who has seen what you are experiencing before.
 
I’d also check the condition and tension in the small flat belt that drives the intermediate pulley / water pump from the crankshaft damper.
It drives both the alternator and the water pump, so if the load from the supercharger caused it to slip enough, you could see lower rpm indicated as the alternator slowed.
I’m not sure that would also cause the overheat, unless the cooling system was already marginal with blocked elbows.

.
 
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The reason I asked is that there is a rubber seal that seals the air box to the intake hose. It is easy to knock this off when removing the air filter. It then gets sucked into the supercharger and sticks to the supercharger lobes. Thus the extra load on the supercharger. Simple to clean the rubber off the lobes with white spirit.
 
A_8 said:
Perhaps also check the oil for water or the coolant for soot/oil residue.
Click to expand...

Head gàsket fine. Check oil and coolant every time before starting engine. No issues there. Oil clean and constant level. Coolant still bright green with no emulsification. Engine has got hot but never boiled. I don't like it getting hot and back off asap when she goes towards 100.
 
tico said:
The reason I asked is that there is a rubber seal that seals the air box to the intake hose. It is easy to knock this off when removing the air filter. It then gets sucked into the supercharger and sticks to the supercharger lobes. Thus the extra load on the supercharger. Simple to clean the rubber off the lobes with white spirit.
Click to expand...

Thanks Tico. That seal is there. When checking for non return I removed the airbox and checked seals. The supercharger moves very freely by hand. Judging by the temps of it's exhaust port it is also making good compression because they get plenty hot plenty quick.
 
Clue is in the first post
“decrease in revs for cruising speed from 3200 to 3050 for same speed.”

Having eliminated any boost pressure leaks by checking the pipage integrity and Y valve functionality then I suspect it’s been running at excessive EGT,s due to the slight overpropping .
Any excess kg,s by tossing in a few seasons accumulation of cruising stores and recent summer fouling growth on the props etc will amplify the load requirement to reach “ cruising speed “

So it may be the exhaust valves have distorted leading to a poorer fit and the turbo vane tips burnt off ,opening up a significant gap thus a drop in boost pressure on that engine .Aircraft buzz noise the sound of this happening?

Eventually and some time later the water jacket temp rises .Rate of rise dependant on the state of the cooling system generally .If its in good condition then unfortunately the rise is slow ie clear jets in the exhaust elbow and a recent HE flush , fresh fully functional water pump etc .
Paradoxically a healthy cooling system masks the prolonged rise in EGT .
Any weaknesses then it’s more likely to show up a rise in water temp .

Once allowed to cool the valves kinda reseat best they can , worn but semi functional just prematurely permanently aged .
Turbo is permanently damaged hence the loss of boost it can’t take over from the compressor which is where you are now .
You need both engines to plane .

Eventually “ at cruise “ slowly it shows up in a water temp rise ( in the absence of EGT guages ) but by that time the damage is allready done .
 
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