Volvo Penta KAD 42 - Low Rev & Speed Problem - Need Help

[Supercose]

Hi ;

I have 1995 Wellcraft Martinique 27 with single Volvo Penta KAD 42 B.

Boat was cruising with max 3800 rpm and 35 knots but one day it just stucked with max. 2300 rpm and 7 knots at full throttle.

Then engine overhauled, turbo, compressor, injectors, diesel pump, intercooler, all filters changed.

Hull and propellers are good, fuel tanks clean and fuel flow is ok.

But the problem is same.

On idle, boat reaches max. 4000 rpm which is very good but on load it stucks at 2300 rpm and 7 knots.

Even there are no any smoke and unusual sound. (Compressor kicks in at 1800 rmp but boat wont go more than 2300 rpm)

I just checked may times with volvo penta mechanic and could not found any air leak or else.

What should the problem be ?

I test the boat many times with 2 people and 8 people still same problem.

I changed the propellers, put smaller ones for testing but same.

I would be glad if you can advice where should i check more or do i miss any points to check ?

Thanks

 

[Reefencounter]

Hi

I still havent fixed the problem, however, a second opinion suggests it is a clogged/blocked exhaust manifold. If this is the case, extra air cant get in as air cant get out. I am getting my mechanic to remove the exhaust manifold, clean it and pressure test it then fit it back on and I will see if that fixes the problem and I will let you know the result

 

[Scott Danforth]

Have your turbo checked as well as pump timing

 

[Supercose]

Reefencounter, I will also check for exhaust manifold. Also i will be waiting your replies once you check your exhaust.

Scott Danforth, turbo is very well and also replaced one more new turbo just to check and result was same. For the diesel pump timing, i have check twice with mechanic and pump timing was ok.

Same as Reefencounter, next step may be checking exhaust system however, if there is no any smoke and unusual sound while on load, there should not be any problem with exhaust system.

 

[Scott Danforth]

new doesnt equal good. check boost pressure at the turbo outlet, check boost pressure at the intake manifold, check exhaust back pressure, and check EGT.

my guess is that you are down significanly on boost

 

[K-2]

Scott is correct, get a boost reading.
Good turbo boost will rule out a lot of scenarios.

 

[Supercose]

Sorry Gents ;

Today we check the boost pressures and they were fine. Not perfect but almost perfect.

Also just to try, we connect brand new compressor and we changed the proppellers from B4 to B2. (we put smaller proppellers)

And nothing changed. Still 2300 rpm with 8 knots speed under full throttle.

Just to try and make a fantasy, my mechanic maximize the (up to maximum limit) fuel flow calibration over diesel pump and increase the idle rpm to 1100. Once we sail with these bizzare, fantasy adjustments we only reach 2800 rpm on full throtle.

So the problem is still same. No air leak and engine overhauled.

KAD42B' s are not electronic engines, they are simple mechanic ones and all soundings are good.

What should you advice and where should look next ? Should it be transmission ? (Proppellers are spinning fine by hand on idle)

 

[Scott Danforth]

Sorry Gents ;

Today we check the boost pressures and they were fine. Not perfect but almost perfect.

This has me concerned. what were the boost numbers and what are they supposed to be? the published boost is actually a minimum requirement to get published power at corrected temperature and pressure.

its either a fuel delivery issue, a fuel timing issue, a fuel return issue, a fuel quality issue, a boost issue, an exhaust restriction issue, or a lack of compression.

 

[Scott Danforth]

I did a google search. plenty of posts on various forums on the KAD42 and low power.

some had to do with supercharger kicking out (models with both supercharger and turbo)
some had to do with miss-adjusted throttles after a service event
some had to do with bad timing
many had to do with fuel quality/filter contamination/pickup strainer plugged
many had to do with low boost pressue
many had to do with oil soaked charge air cooler (from a failing turbo).

 

[Supercose]

Dear Gents ;

Thank you very much for your comments.

Problem is solved.

I called a new mechanic from Istanbul and we had a sea trial.

My mechanic informed me that there are two main timing on KAD42's.

First main timing is fuel timing which is done on diesel pump and other is air timing which is done somewhere under kompressor brain.

And my mechanic informed me that there is a ratio between these two.

My boats air timing was under standard level and fuel timing was a little over standard thus made insufficient power.
So my mechanic made both two timing and ratio calibrations just in 10 minutes and then boat just cruised 3800 RPM with 33 knots.

Problem is solved.

Thx again for your comments.

 

[Fish Canada]

I don't think I want a diesel anymore.

 

[Tiam1838]

Hi Supercose,

i have ave the same problem as your boat in Singapore. Do you have details or diagrams where I can advise my mechanic to adjust both the fuel timing and air timing because I have consult with them and my mechanic have no idea on where to adjust it. Please advise, thanks.

 

[GA_Boater]

This thread is almost three years old and Supercose has not been here since starting the thread.
Please start a new thread of your own.

Closed.