Volvo Penta KAD 42 loss of revs.

[SovereignDiver]

Both tanks recently cleaned, fuel polished of crud and debris, prefilter strainer and spinners cleaned and primary and secondary diesel filters replaced.
Both tanks refuelled.
Both engines start and run well however, once on the plane for 15-20 minutes there is a decrease in revs on port engine from normal cruising 3,400 down to 3,200. Increase throttle but cannot increase revs even moving up to throttle stop.
Starboard engine no problem retaining 3,400 rpm cruising setting with revs under load increasing to 3,800 max at throttle stop.

Have checked the air filters and they are fine. Any ideas where I go next?

Cheers

Mike

 

[Peanuts]

Hi
Do we assume you have had fuel problems in the past? I think the answer is yes!

I have to say I would probably be looking at some thing restricting the fuel flow on the port engine. It might be in the filters or could of course be debris in the fuel line before the filters.

Does each engine have seperate fuel lines going to each filter or is it a common line going to each filter?

Sorry for all the questions but it should help us to help you if you see what I mean.

 

[SovereignDiver]

Hi Peanuts.

Many thanks for the response.

Both tanks and filters are independent with independent fuel feeds.

The dirty tanks and fuel problem was identified prior to purchase hence the tanks being cleaned and the fuel polished.

At the time, the secondary filters were changed as were the primary paper cartridges, however, the company did not remove and clean out lower part of the primary filters housing the centrifugal seperators and bleed valves.

At the weekend I took both primarys apart (they were very dirty and had quite a bit of crud in them). I have thoroughly cleaned them replacing both primary paper cartridges. I have also replaced the secondary in line filters as a precaution. Took a prolonged test run and found the port engine still reducing revs to 3,200 (Drat!)

I will investigate again and check the flow from each fuel line to the primary filters.

In the interim are you aware of any other issues affecting KAD 42 revs please let me know.

Cheers

Mike

 

[Greg2]

Might be worth checking your props. Last month I experienced what I thought was a loss of power in the stbd engine (KAD 42's). Barely reached 3000 revs, even at WOT, whilst the port engine reached normal revs and was responsive to WOT. Many hours spent going through the fuel system - stripped it all out and checked for blockages etc. Chance observation by a pal led me to check the props and it turned out that the problem lay with the port props as opposed to the stbd engine. VP duo props have rubber inserts that rely upon friction to bond the prop to the hub and they had failed.

Visiting boat with a marine engineer aboard subsequently said it was the first thing that came to mind when he heard the symptoms.

I know this isn't exactly the same symptoms as you have but they are similar and probably worth a check.

 

[Peanuts]

I always stand to be corrected, but if the props were slipping on their rubber bushes would not the rev's be higher not lower? Just like a slipping clutch on a car for example.

 

[Pendana]

If port props "loose", port engine will rev normal but not produce any power. Starboard engine has to do all the work and doesn't achieve full revs.

 

[SovereignDiver]

Have to support Peanuts on that one as I am not maintaining revs and losing speed, I am losing revs and hence resultant reduction in speed.

In any case I value all postings as I know formurites can solve 99% of all known problems.

Many thanks

Mike

 

[SovereignDiver]

Hi Pedana.

Just spotted your post so need to confirm what is happening.

Initially accelerates and gets onto the plane and reaches my prefered cruising speed at 3,400 revs. Port engine, after about 15 mins loses about 200 revs. Starboard engine will still rev to max and when doing so can feel the force of acceleration and speed increase.

I do not think the port engine is carrying the burden of possible slipping props on the starboard side so I am still leaning heavily toward Peanuts on this one.

Many thanks for your post.

Mike

 

[Pendana]

Sorry to thread drift a bit, I was just trying help explain how Gregs problem was. Sometimes an apparent poor performing engine is actually ok but is having to work harder due to the other not performing.
I dont think your problem is the same as Gregs was, yours sounds more like fuel or breathing problems. Do you have boost guages fitted? Are both turbo's providing similar boost?
It's as if you loose a bit of power once they are fully warmed up.

Good luck anyway.

Eddie

 

[SovereignDiver]

Good morning Pendana

No problem and thanks for the further information. I don't have boost guages fitted to the turbos so don't know if this could be a fault.

Do you have boost guages fitted? If so what make?

Cheers

Mike

 

[Pendana]

I have the volvo boost guages fitted. Bought them for my last boat and transferred them to current one. Use to get them as a kit but I think you now have to buy the sensor & guage separately which of course doubles the price!!. Easy to fit though, the cable between the engine and helm is unused amongst the 16 wire umbilical.

Eddie

 

[SovereignDiver]

Good afternoon Eddie.

Any help on where I can buy these items would be of great assistance.

Cheers

Mike

 

[Pendana]

Good afternoon Eddie.

Any assistance on where I can buy these items would be of great assistance.

Cheers

Mike

I got mine from Volspec. You can contact them on 01621 869756.


Eddie

 

[SovereignDiver]

The plot deepens, so one for an engineer?

So fuel now appears OK (most probably always was), air filters OK (most probably always were).
"Off load test" on both port and starboard engine show both rev to max revs, smoothly and from what I can see show identical curves of accelleration from tickover through super charger range achieving 3,800 revs no problem.
Under load port engine will still only rev to 3,400 dropping off to 3,200 after about 15-20 mins cruising.
Now for the new piece of information.
Turned to port at sea, reasonably tight turn, revs on port engine dropped off to about 2,700 and took some time to pick back up to 3,200. No contact made with throttles, this all happened by itself and I am not sure if there was any other background noise.
Got close to home and tried the same manouvre again just to check, same turn to port and the engine revs dropped even lower (about 2,000) and into supercharger territory where the supercharger kicked in. I think there was other noise in the background masked by the supercharger but I couldn't identify it.
I immediately decelerated both engines, dropped off the plane, and got back to the marina at displacement speed.
Trailered both legs and checked props which are all fine with little fouling on the legs.
Checked for rotation and all props free rotate by hand, no obvious signs of grinding or other damage.
I think there is a leg problem on the port side but don't know what could possibly cause the above symptoms.
Any ideas on this one would be gratefully received.
Many thanks
Mike

 

[spannerman]

It could be the bearings in the gear set in the top section of the drive or the bearings on the intermediate shaft coming throught the transom, either way you need to remove the leg to check them.
When you turn the steering there is a significant side load generated by the universal joint having to spin through an angle so this all points to the upper section of the drive train.
Do you have any noise at the drive when in neutral and on full lock, if so sounds like water in the bellows and a seizes U/J, which will really load up the bearings.

 

[SovereignDiver]

Hi Spannerman

Many thanks for the info.
I take it with either bearing or drive train problems the engine is struggling to cope with the load hence the drop off in revs?
Only asking because I have decided to go for a full lift chock and investigation tomorrow.
Anyone confirm or have any other ideas?
Cheers
Mike

 

[SovereignDiver]

Where's Naylorman (Doublevision), Volvo Paul et al when ya need em?

 

[DoubleVision]

Hi Mike. I`ve never had this prob with all the DP legs I have owned but Spannerman seems to have something there. When you have the lift and if nothing seems to be wrong swap the legs over and see if the problem changes to the other engine. I dont think its prop slippage as I have had that. The affected engine just revs its nuts off with no go. Fuel system sounds clean enough to serve beer through now but it might be worth checking the lift pump. I had to replace one on Double Vision and that did give me another couple of hundred revs. The diaphragm they recon had a pin hole puncture in it. Has the boat had this problem this since you bought it or has it recently come on?

 

[SovereignDiver]

Hi Paul.

Thanks for that. The only reason I'm looking to the leg is the turn problem that manifested itself on Saturday as described earlier.
Anyway she's coming out for her annual tart up early anyway as I am not sure if the antifouling may be spent as are the anodes. So the legs will also get a thorough inspection and overhaul.
Engineer still thinks its fuel and maybe we'll do further tests on this when she is back in. As I have posted previously I have completely cleaned and purged the line up to the primary filter, we will looking to the rest, i.e. check between primary and lift pump, lift pump and secondary, secondary to and including injector pump, and finally injector pump to injectors inc injector checkover.
Phew, have I missed anything or anyone else got any ideas?
Ta
Mike

 

[SovereignDiver]

The plot thickens!

Boat lifted out and full annual maintenance completed.
All running gear checked, props and legs all fine. Hull cleaned, antifouled, and ready to go.
Back in water.
The very next cruise. Trip to St Kats in London with all going fine until entering the Thames and slowing at the various bits you have to slow down for. Again port engine slow to respond with power band kicking in at supercharger revs but not powering thru turbo territory (at this stage I still do not think it is a turbo issue for reasons that follow later).
Having got to London outside St Kats on decelerating and changing to neutral, port engine cut out. For the whole trip to London all pressures and temperatures were fine, no additional smoke or any unusual noises from anywhere. Tried to restart, the engine restarted then cut out again.
The engine would not run so berthed on starboard engine alone. After about 15 minutes when engine had cooled below op temp, it started after a slightly prolonged starter engagement and ran fine. Checked primary filter and centrifuge all fine with claret clear red, no dirt, no water, changed secondary filter "just in case"!
Coming back from London yesterday port engine gets to 3400 cruises ok for about first hour to hour and a half. Any change in throttle after that and it is slower to respond and can only achieve 3200 to 3300 max.
Got back to the Medway safely and port engine stopped on deceleration and change to neutral, engine would not restart. Locked in to Chatham on starboard alone.
Port engine restarted in lock but then cut out again. Engine would not restart so berthed on starboard alone.
Waited 15 to 20 minutes port engine started again after prolonged starter engagement.
So, any idea’s on what is wrong or what I need to do next would be greatly appreciated.
Ta
Mike