D4 260s low turbo pressure on one engine

[wivsi]

Hi,

Possibly a bit early to be asking for advice but … we have twin D4 260s and yesterday on first decent run of the season I noticed stbd engine reporting about 40% lower turbo pressure in the EVC, compared to port. I did not notice any major performance issues and if anything this engine was showing higher revs than the other for same throttle settings. But, eg at around 2500rpm I had 100 on the port turbo, 70 on the stbd.

We were on way into port with a deadline so had limited time to experiment but from a quick test we seemed to be able to get up to full speed and full revs. I need to test this again but wondering if anyone has any quick ideas before we head home. Or do I ignore it…

If I need a Volvo mechanic I’ll be leaving the boat closer to them in a different port!

Cheers

Simon

 

[vas]

prop bush slipping?
said engine does less work, revs higher, other engine does most of the work higher load hence turbo boost...

 

[wivsi]

prop bush slipping?
said engine does less work, revs higher, other engine does most of the work higher load hence turbo boost...

That sounds annoyingly believable. Is that checkable by feel or does it need taking apart…?

 

[simonfraser]

if the prop bush is plastic or similar it would wear out fairly rapidly and thus get worse ?

(VP D4 issue or prop, my bet would be on the D4)

 

[SC35]

Paint a line across the cone and the two hubs ... then another test run ... get back and check the line is still a line when rotated into place.

 

[SC35]

if the prop bush is plastic or similar it would wear out fairly rapidly and thus get worse ?

(VP D4 issue or prop, my bet would be on the D4)

Once a prop bush starts to slip, it just gets worse.
I wouldn't recommend re-hubbing them either - a new prop is the fix.

 

[wivsi]

Thanks all. I didn’t think of the line on the props but had a good thrash on the way back home this morning. Really noticeable that, when pushed to WOT, revs and turbo both shot up on the trouble side, like there was not enough drag on it. So slipping prop sounds like the issue.

I’ll try marking that line across to confirm.

Damn, more lifts and more work….

 

[SimonD]

Thanks all. I didn’t think of the line on the props but had a good thrash on the way back home this morning. Really noticeable that, when pushed to WOT, revs and turbo both shot up on the trouble side, like there was not enough drag on it. So slipping prop sounds like the issue.

I’ll try marking that line across to confirm.

Damn, more lifts and more work….

Would it be possible to lift the drives enough to reach the props and scribe a line (maybe with a rasp or something similar). If not, can they be reached from the water. It would save a lift.

 

[wivsi]

Would it be possible to lift the drives enough to reach the props and scribe a line (maybe with a rasp or something similar). If not, can they be reached from the water. It would save a lift.

Yeah I will be able to at least do this in the water. Will get on a paddle board and reach it. I was just looking ahead to the inevitable lift and more bills...

 

[SC35]

Yeah I will be able to at least do this in the water. Will get on a paddle board and reach it. I was just looking ahead to the inevitable lift and more bills...

On mine, it's actually possible to change props from an inflatable tender, using a block of wood to chock them off.
I ruined a ratchet wrench in the salty water, but it was much cheaper than a lift out.

 

[wivsi]

OK thanks, might take a look!

Another question for the experts, if it's slipping props... the drives have just had a full service. Would the props have come off for this? Is it potentially linked to the service, or is this just ... unrelated coincidence? Any thoughts?

 

[volvopaul]

OK thanks, might take a look!

Another question for the experts, if it's slipping props... the drives have just had a full service. Would the props have come off for this? Is it potentially linked to the service, or is this just ... unrelated coincidence? Any thoughts?

Props need to come off to drain oil , no I doubt it’s an assembly problem but if you lift the drives check the gap between the two props if they have closed up the bushes are worn . A word of advice don’t send them to Steel Development they are not very honest , I have previous experiences.

 

[wivsi]

Props need to come off to drain oil , no I doubt it’s an assembly problem but if you lift the drives check the gap between the two props if they have closed up the bushes are worn . A word of advice don’t send them to Steel Development they are not very honest , I have previous experiences.

Cheers Paul. Good to know. Got any recommendations for the job…? PM me if easier - any help appreciated!

 

[SimonD]

So, this problem came to light on the "first decent run of the season", I presume the first after the drives had a full service. Quite a coincidence. Call me a cynic, but I wouldn't be terribly surprised if the props had not been put back properly. It is possible, even for a professional engineer, to get it wrong.

 

[volvopaul]

Cheers Paul. Good to know. Got any recommendations for the job…? PM me if easier - any help appreciated!

Where is the boat ?

 

[wivsi]

Where is the boat ?

Deepest Essex!

 

[Seastoke]

Paul if you go, get out before dark.

 

[wivsi]

TBH it’s better after dark. Can’t see what’s going on around you.

 

[SC35]

So, this problem came to light on the "first decent run of the season", I presume the first after the drives had a full service. Quite a coincidence. Call me a cynic, but I wouldn't be terribly surprised if the props had not been put back properly. It is possible, even for a professional engineer, to get it wrong.

With a DP-H drive, either the props are attached, or they have fallen off.
There is a spiral thread on the shaft: the only way a prop can spin on the shaft is if the hub is knackd.

 

[SimonD]

With a DP-H drive, either the props are attached, or they have fallen off.
There is a spiral thread on the shaft: the only way a prop can spin on the shaft is if the hub is knackd.

I stand corrected. Still quite a coincidence though.