VP D6-310-DPH- Not reaching max RPM

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Pet_1

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Hello
I have read on the forum many posts regarding the issues of engines not reaching WOT.
I have a twin engine set up and both engines will only reach 3000rpm.
I am currently waiting for the engineer to visit the boat but he said it was probably a boost sensor. This I can understand if it were effecting only one engine or is this some sort of engine management or RPM syncing that is making both engines RPM the same. I was thinking it would be something common the both engines which can only be fuel. I haven't had time to do any investigation myself apart from this.
Engines with no load = 1500rpm, which is correct.
On one engine under load = 2200rpm, both are the same. ?
Both engines start perfectly and run without smoke.
I plan on looking at the filters this weekend but they have only had 500ltrs through them at the most since being fitted in May 2018.
I would appreciate any feedback, Thanks.
 
If it was fuel related you’d have alarms sounding & warning messages displayed in the tachometer screens. As you’ve not mentioned any alarms I’d suggest it’s not a fueling problem.

It could be the boost sensor on one or both engines, as they do make the engines do strange things & don’t trigger any alarms. If it was one (sensor) rather than both I’d expect one engine to be struggling more than the other rather than both being the same. If it was both sensors playing up then it could be the reason for them both having similar speeds.

Is the hull clean, plus the drives and props?

Have you added any significant weight onboard recently?

Easiest way to check the sensors is either with Vodia log test looking at inlet manifold temp., or removing them and checking the resistance with a multimeter.

If on sea trial, the same log test on Vodia can be used to check throttle position (to ensure 100% is being requested) and also engine loading.

I once had a twin installation on a cold day reading 45C on one engine and 100+ on the other, so it’s not unheard of for two to fail on the same boat!
 
Pet_1 said:
Hello
I have read on the forum many posts regarding the issues of engines not reaching WOT.
I have a twin engine set up and both engines will only reach 3000rpm.
I am currently waiting for the engineer to visit the boat but he said it was probably a boost sensor. This I can understand if it were effecting only one engine or is this some sort of engine management or RPM syncing that is making both engines RPM the same. I was thinking it would be something common the both engines which can only be fuel. I haven't had time to do any investigation myself apart from this.
Engines with no load = 1500rpm, which is correct.
On one engine under load = 2200rpm, both are the same. ?
Both engines start perfectly and run without smoke.
I plan on looking at the filters this weekend but they have only had 500ltrs through them at the most since being fitted in May 2018.
I would appreciate any feedback, Thanks.
Click to expand...

All the boost sensors I’ve changed that were faulty have only allowed an in gear under load max rpm of around 1200 at full throttle , with very little throttle response from idle, 1500 in neutral is quite normal , nothing much can be achieved from that reading , check the neutral light isn’t on, although when the shift actuator neutral switch has failed it only gives 1500 in gear as the ECU limits the rpm.

If the hull and props are dirty I’d suggest that’s your problem , or a slipping prop hub.
 
Thanks for the quick reply Andyroonot.
I agree about the fuel, I was just looking for something common to both engines and I have not had any alarms.
Hull was copper coated in May and looks good around the waterline, also 4 new props fitted in May.
Not added any weight in fact fuel half tank, 500ltrs, water and holding tank empty so less than normal.
Do you or anyone know the resistance of a good sensor.
With regard to the throttle position I noted the levers had about 20% travel left after reaching 3000rpm. I calibrated the throttles but this made no difference.
 
New props have lost there shine but they are all there and free from weed and barnacles. Reason for new props was the port front hub failed causing it to crash into the back one.
 
Given electronics are involved idle RPM and single engine RPM tend not to mean much as the electronics take over.

Similarly in most cases the RPM are synchronised.

If the props are dirty and you request full power you will typically also see the temperatures rise ( if it UK based given water temp I cant gtee that) but in the med it can show a significant temp rise if the props and hull are dirty.

From your consumption figures (500 lts) it will have only done 5 or so hours in 9 months - so unless you have just had it cleaned take the advise of others - I suspect it has no fault.
 
500lts is what is currently in the tank in respect of the boats load as in it is lighter now than it has been this summer.
Usage since May about 40hrs. Usage in the last 3 months about 5hrs.
Props are clean, hull has copper coat so should be clean.
I was of the understanding that a dirty bottom would more likely reduce the speed not the RPM.
Temp readings all normal.
 
copper coat takes at least 18 months to 2 years to become properly effective. I suspect underneath it's dirtier than you might imagine.
if engines show no faults and the boat is just reluctant to go its almost certainly just fouling.
As to how much fouling is too much can vary considerably from boat to boat. How much fouling re use of boat is also impossible to answer as it depends on so many things.
Best thing to do is keep an eye on things over several seasons and learn from that.

the engines can only increase in RPM up to max RPM if the applied load is within the design limits
once the resistance to movement is too much the engines, however well looked after just can't do it.
 
Last edited:
Thanks to all.
I plan to have the engineer come and make some vodia checks and see what he comes up with. I will then lift the boat as soon as possible and have a look at the bottom and get everything serviced all be it a few months earlier than planned.
 
If he finds no fault I would not lift it early - you will only start the season with dirty / hull and props.

Where is the boat? Mine is in the med and after 4-5 weeks ( with the boat mostly in use) the prop fouling is bad enough to warrant diving with tanks to clean them,
 
Was the loss of power sudden or gradual?
If it were just after prop change it could be wrong size props but you would have noticed it immediately!
 
When have you cleaned the props ?
Have you ever cleaned them ?
Does sound like dirty props .Those VP duo prop set ups are very sensitive to slightest film , if they are rough to the touch in a sandpaper kinda way - that’s where your extra rpm has been lost .

I took up scuba diving ( bought the kit ) just to clean the props .
 
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