Starboard engine cant decide what RPM it should stay at. Volvo Penta D6-370

bluemoon78 · 29 Jun 2022

I can cruise in 35 knots (2800 rpm) for hours straight without any problems and then suddenly starboard engine will go up and down in rpm. I goes from 2800 to 1200 and somtimes right up again to 2800. If i dont thouch the tbrottle it will keep doing the jumps in rpm. Its like the SB engine suddenly cant decide what RPM it should stay at.
Most of the time it fixes itself if just touch the throttle a little (take both engines up to 2900 rpm, or down to 2700). but sometimes I have to take both levers all the way down and then back up again to "fix" the problem. Then it can go hours before it happens again.

Alle filters have been changed. Filters are clean. propeller are new,

It seems like the engine looses syncronisation of the lever or that the EVC doesnt know possition the SB lever is in.

I have tried to calibrate the throttle without any luck

Any ideas ?

2 x D6-370 from 2008 - 600 hours - (Single diesel tank)

Sorry for my bad English

Portofino · 29 Jun 2022

The port engine prop bush ( if it’s a sterndrive ] on its way out , loosing grip intermittently.

bluemoon78 · 29 Jun 2022

Thanks for trying to help Portofino. I was thinkin about that, but would a slipping bush "fix" itself by wiggling the throttle just a little bit ?

SC35 · 29 Jun 2022

bluemoon78 said:
Thanks for trying to help Portofino. I was thinkin about that, but would a slipping bush "fix" itself by wiggling the throttle just a little bit ?

No, it wouldn't.
I've had slipping prop bushes, and the symptoms are that one engine revs higher than the other when you try to get on the plane.

Sorry, I have no idea what your problem might actually be.

julians · 30 Jun 2022

faulty throttle potentiomer in the throttle lever?

Just guessing really.... but its cheap and relatively simple to fit a new throttle potentiometer. Other option is to get a volvo penta technician with the laptop to diagnose the problem properly.

volvopaul · 30 Jun 2022

Check the plug on the boost sensor

sammyadam · 30 Jun 2022

bluemoon78 said:
I can cruise in 35 knots (2800 rpm) for hours straight without any problems and then suddenly starboard engine will go up and down in rpm. I goes from 2800 to 1200 and somtimes right up again to 2800. If i dont thouch the tbrottle it will keep doing the jumps in rpm. Its like the SB engine suddenly cant decide what RPM it should stay at.
Most of the time it fixes itself if just touch the throttle a little (take both engines up to 2900 rpm, or down to 2700). but sometimes I have to take both levers all the way down and then back up again to "fix" the problem. Then it can go hours before it happens again.

Alle filters have been changed. Filters are clean. propeller are new,

It seems like the engine looses syncronisation of the lever or that the EVC doesnt know possition the SB lever is in.

I have tried to calibrate the throttle without any luck

Any ideas ?

2 x D6-370 from 2008 - 600 hours - (Single diesel tank)

Sorry for my bad English

I had the same issue with my Starboard engine last year, I have the same engines and year with the electronic shifters. Do you also find that when you put your Starboard shifter into position one (idle forward) that the shift hesitates and you need to give it a little push forward for it to engage.

bluemoon78 · 30 Jun 2022

Did you find a solution for the problem?

I dont have any problems with shift

sammyadam said:
I had the same issue with my Starboard engine last year, I have the same engines and year with the electronic shifters. Do you also find that when you put your Starboard shifter into position one (idle forward) that the shift hesitates and you need to give it a little push forward for it to engage.

Bilgediver · 1 Jul 2022

bluemoon78 said:
Any ideas ?

Is it an electronic throttle? If so it might be an electrical problem. Like a noisy volume control on a radio. Maybe you are too young to remember those problems

Corona Mia · 1 Jul 2022

Isn’t there some sort mechanism (or software) which synchronises revs between the two engines?
Could it be an issue with that?

sammyadam · 2 Jul 2022

bluemoon78 said:
Did you find a solution for the problem?

I dont have any problems with shift

No still I am looking for it to solve it.

A_8 · 2 Jul 2022

Sounds like a faulty throttle potentiometer in the throttle lever but I have no experience.
Is it possible to swap the controls so that the starboard control operates the port engine ? If so you can confirm if its the control as the problem moves to the other engine.

Portofino · 2 Jul 2022

Why is it not throwing up any codes if it’s electrotwackery related ??

jcwads · 2 Jul 2022

Prop bush was my issue on mine, same symptom.

Bilgediver · 2 Jul 2022

Portofino said:
Why is it not throwing up any codes if it’s electrotwackery related ??

Maybe the electrotwackery thinks it is an erratic intoxicated skipper on the helm so accepting the erratic behaviour.

bluemoon78 · 2 Jul 2022

jcwads said:
Prop bush was my issue on mine, same symptom.

RPM goes down, never further up then it was.-
Prop are new and re-checked and they are fine.

bluemoon78 · 2 Jul 2022

A_8 said:
Sounds like a faulty throttle potentiometer in the throttle lever but I have no experience.
Is it possible to swap the controls so that the starboard control operates the port engine ? If so you can confirm if its the control as the problem moves to the other engine.

I just order new potentiometer for the sb lever and a new MAP sensor for the sb engine. I hope its one of the two.

I have changed propellers, both fuel filters, and air filters, so potientometer and map sensor is they next on the list.
Getting a Volvo Penta tech with a laptop is unfortantly not possible where i live. Well, its possible but it would cost more then the boat

bluemoon78 · 2 Jul 2022

What do you guys/girls think about this explanation?

Faulty neutral "switch" on the gear actuator. And therefore the actuator send neutral/no-neutral signals to EVC that the gear is in neutral (and limiting the RPM to 1500 rpm) causing the erratic RPM.

Am I WAY OFF ?

A_8 · 2 Jul 2022

bluemoon78 said:
What do you guys/girls think about this explanation?

Faulty neutral "switch" on the gear actuator. And therefore the actuator send neutral/no-neutral signals to EVC that the gear is in neutral (and limiting the RPM to 1500 rpm) causing the erratic RPM.

Am I WAY OFF ?

Again I have no experience of the electronics of this particular engine but I would assume this would throw a code and put the engine in limp mode until you restart and it happens again.

Andyroonot · 2 Jul 2022

If you want to prove the throttle as the issue (or prove it is OK!) before changing anything then undo it from underneath, turn it 180 degrees, swap the two HCU connections and then recalibrate. If the problem switches to the other side then you’ve found your fault

Starboard engine cant decide what RPM it should stay at. Volvo Penta D6-370

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