Twin KAD32 can't get over 12 kts

[Somerset Taz]

Hi, this year's first WOT experience was a worry and I'm after thoughts suggestion from the forum gurus please. Situation: 29 foot cruiser with twin KAD32s with low hours (300). Recent SC issues all fixed (see previous posts) and fully serviced just before lift in. They both start first turn and in neutral, rev up normally though the range with SC cutting in and out correctly. Lift in was mid April, cruised 6 nm at 6 kts to mooring with no issues - all T&Ps normal. Unfortunately we were not able to go back to the boat until this week (mid June). Again both engines started perfectly, 20 mins at 6kts to open water then time to open her up..... Push both throttles to WOT, acceleration ok to start with, but could not get the boat to more than 12kts at 3000 revs and obviously could not get on the plane. This was unexpected as usually the boat is up to 17 kts in no time and planning, and last year consistently got to 27-28 kts. Tried a more gradual throttle opening to WOT twice, SCs were engaging/disengaging fine but each time bogging out at 2900-3000 on both. In neutral the engines rev up to the rev limit no problem.

As both engines are affected my thinking:
Has the "dirty Dart" finally defeated my coppercoat of 9 years and this is a fouling issue after only 2 months of inactivity (apologies have not been under the boat but the sides seem to be only slimed - props look ok)?
Is last year's diesel causing an issue on both engines?
Are there residual fuel bleeding issues on both engines after all filters were replaced during the above mentioned service?

Any thoughts would be gratefully received.

 

[stelican]

Were the engine producing black smoke trail on water. This can be caused by turbos sticking.

 

[Somerset Taz]

Hi Stelican. Thanks for your thoughts. Whilst I did not specifically look for a black smoke trail, I did look down to check the outdrives and did not notice anything, as I recall there was a clear wake from both legs. The engines have never been smoky. I'm perplexed that if it is a turbo sticking issue why both engines at the same time?

 

[scottie]

I would be checking out fuel system
Lack of smoke is an indication of fuel

 

[stelican]

Hi Stelican. Thanks for your thoughts. Whilst I did not specifically look for a black smoke trail, I did look down to check the outdrives and did not notice anything, as I recall there was a clear wake from both legs. The engines have never been smoky. I'm perplexed that if it is a turbo sticking issue why both engines at the same time?

If there's no black smoke / black unburnt black fuel trace left in the wake it's not the turbos

 

[aerobat]

Imho a bad turbo on one engine . It does not smoke because it has a boost sensing fuel pump but lacks on power . The other engine is ok but simply not powerful enough to speed the boat "alone" and rev rated rpm,s

 

[Chris_d]

If it's not been used for while, change all fuel filters and clean the props and drives and as much slime off the hull as you can, then it will go.

 

[Somerset Taz]

Thanks to all for your thoughts. As the fuel filters were changed at the service (so around 2 hours usage ago) and the old ones pretty clean, I don't think these new ones need changing again. However, possibly they were not bled thoroughly enough at the time. So I will bleed them again next time I'm down to the boat to rule that possibility out - or fix the issue. Are there any top tips on bleeding KAD32 injector(s) please - I would like to be as sure as I can be that there's no air in the fuel system.

 

[Momac]

If the lack of performance started after the engine service then does this not indicate something done wrong at service ? Changing fuel filters again is not too expensive and the easy first step.

 

[FatherTed]

Greetings - glad all is well with the electronics

1. Check the proximity sensors are working ok and the throttle arm touches them at WOT - then when running and at WOT these will keep the supercharger engaged until ~3100 RPM, vs ~2600 RPM with a normal disengage.
2. Has the airfilter pipe / flap assembly been removed? - check the rubber interconnect hose has not been tucked under. With the SC running you will feel a blast of air. (Happened to me after a service recently)
3. Check the fuel valves are fully open and the cross-feed valve is correct.
4. Check both SC are actually running.
5. Remove exhaust elbow, check turbo spins freely. Take a photo of the blades.
6. Go for a swim and clean the hull - it's warmer now.......

 

[Somerset Taz]

Greetings - glad all is well with the electronics

1. Check the proximity sensors are working ok and the throttle arm touches them at WOT - then when running and at WOT these will keep the supercharger engaged until ~3100 RPM, vs ~2600 RPM with a normal disengage.
2. Has the airfilter pipe / flap assembly been removed? - check the rubber interconnect hose has not been tucked under. With the SC running you will feel a blast of air. (Happened to me after a service recently)
3. Check the fuel valves are fully open and the cross-feed valve is correct.
4. Check both SC are actually running.
5. Remove exhaust elbow, check turbo spins freely. Take a photo of the blades.
6. Go for a swim and clean the hull - it's warmer now.......

Hi Father Ted;

Yes all's well with the electronics thanks....
Will check all those points as well as re-bleeding the filters. I may also brave the dirty dart and hope that I can see through the murk to clean the hull - last time the water was like gravy, with visibility from the surface of about a foot!
I'll report back with results and hopefully pictures.
Cheers.

 

[New Boater]

I bought a boat last year in Guernsey, travelled over for a sea trial and the boat did nit perform as it should have on her Kad32’s.

It was sticky Turbo’s she struggled to get on plane even though the SC’s were singing away!

The seller had both turbos replaced (very nice man) and when I went back to test she literally jumped out the water on Throttle up!

Anyway, when she was not working due to sticky turbos she was leaving a significant smoke trail, almost embarrassingly so!

So I second the sticky turbo smoke thing!

Good luck! I love my 32’s

 

[New Boater]

PS, i bought a cheap injector test rig and tested all 8 injectors and they were all spot on the same.

I wouldn’t worry about your injectors unless you think they have been clogged somehow, the chances of losing enough injectors at the same time to reduce you to 12 knots is slim.

 

[Somerset Taz]

PS, i bought a cheap injector test rig and tested all 8 injectors and they were all spot on the same.

I wouldn’t worry about your injectors unless you think they have been clogged somehow, the chances of losing enough injectors at the same time to reduce you to 12 knots is slim.

Thank you New Boater, I will be taking a look at the turbos even though I did not notice any black smoke. Hopefully the turbos will be ok on engines with only 300 hrs. I'm hanging my hopes on my poor bleeding of the fuel system when I changed all the filters during the service. I will do this as soon as I can but it won't be in the next couple of weeks as we're expecting another grandchild to arrive any day!

 

[stelican]

Next time you trial the boat if it's doing the same stop boat and reverse course to see if there is partially burnt fuel on water.
Had this happen several times when boat was not used much. 700 engine hours

Thank you New Boater, I will be taking a look at the turbos even though I did not notice any black smoke. Hopefully the turbos will be ok on engines with only 300 hrs. I'm hanging my hopes on my poor bleeding of the fuel system when I changed all the filters during the service. I will do this as soon as I can but it won't be in the next couple of weeks as we're expecting another grandchild to arrive any day!

 

[New Boater]

Thank you New Boater, I will be taking a look at the turbos even though I did not notice any black smoke. Hopefully the turbos will be ok on engines with only 300 hrs. I'm hanging my hopes on my poor bleeding of the fuel system when I changed all the filters during the service. I will do this as soon as I can but it won't be in the next couple of weeks as we're expecting another grandchild to arrive any day!

Good luck with that!!

Congrats in advance.

I have modded the Supercharger brain on my 32’s so I have manual control.

Most of the time I just follow the normal routine of “switch on at 16 and off at 26 and the same back down” but sometimes when I want a slightly less whiny 12 knots I can opt to not switch them on etc, i love it and of course the system is not prone to electronic brain meltdown leaving me with a problem engine.

Anyway good luck again

 

[Somerset Taz]

Thank you New Boater. Yes I have a mod that allows me to switch out the SCs should I want to. I also installed a solenoid switch to isolate the SC speed controller from the clutch current (see an earlier post entitled "first sign of insanity").

 

[New Boater]

Sounds ideal, that post got me to do my mod I think!

I installed a relay to isolate them.

All good!!!

 

[Somerset Taz]

Greetings - glad all is well with the electronics

1. Check the proximity sensors are working ok and the throttle arm touches them at WOT - then when running and at WOT these will keep the supercharger engaged until ~3100 RPM, vs ~2600 RPM with a normal disengage.
2. Has the airfilter pipe / flap assembly been removed? - check the rubber interconnect hose has not been tucked under. With the SC running you will feel a blast of air. (Happened to me after a service recently)
3. Check the fuel valves are fully open and the cross-feed valve is correct.
4. Check both SC are actually running.
5. Remove exhaust elbow, check turbo spins freely. Take a photo of the blades.
6. Go for a swim and clean the hull - it's warmer now.......

Hi Father Ted,
So new grandad duties over for the time being I managed to get to the boat, albeit just for a day. So:
1. Proximity sensors checked all ok.
2. N/A no work in the area.
3. Fuel valves all fully open and cross feed correct.
4. Both SC are running within the correct rev ranges and when WOT (see point 1 - in neutral).
5. Not checked this time
6. Hull not too fouled - just a thin layer of slime and no worse that this time last year (it is copper coated).

So suspecting my inadequate bleeding of the engine fuel filter I rechecked for air again using the hand primer. Fuel through second push on both engines. Went for a quick spin in the bay and could not get over 12kts again (and about 2800-3000 revs max). Tried each engine individually both really struggled. There was no smoke or evidence of unburnt fuel in the wake.
I will move onto your point number 5 asap (check the turbo). However, I'm wondering whether the air intake flapper/check valve(?) in the Y box connected to the air filter box is sticking and restricting intake air to the turbo compressor, so I'll check those next.

Any further thoughts and advice gratefully received. Cheers

 

[SC35]

What speed did you achieve previously at 3000rpm?