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Re: [Amel Yacht Owners] D3-110I-C Wandering RPM

Porter McRoberts
 

Hello Dean, and hive of cognoscenti.

Please have a look at this video if you’d be so kind:



I started noticing your description several months ago. Pre boost pressure sensor fault, pre long block failure. We hauled out in Martinique in April. Serviced c drive, autoprop etc. I noticed that 2 of the autoprop arms fell with gravity alone. The third needed coaxing from a finger. More grease and it was better but never equivalent to the other 2. Minimal vibration. Hard to know how much vibration is normal as only have had the boat 1.5 years. Never motored on another 54 or SM for that matter. 

So.... after finding sputtering oil from the dipstick confirming to Volvo the Long block was shot we had a new long block installed and engine back in the boat Friday with sea trial last Saturday. While out of the water I sanded and acid washed the prop. Still noted one arm stiffer than the other. But not worse that it had been. 

During the sea-trial we had  Lots of rpm variability such as dean described but even +/-50-100 rpm. But not close to what is seen in the video. Our WOT was held to 2360. CDM/Volvo with their vodia computers hooked to the engine blessed it and said it was good. Hands washed they said the variability had to come from the prop. (I had not disclosed my observations under the hull while out of the water). 

This Last Monday real world test: we set out southwest from Panama City to isla Contadora. RPM wandering was much higher- this is when Video was taken. Wasn’t the most relaxing of trips in addition to being late and arriving in the dark we had an explosion of late afternoon lightning storms with webs of red and blue current above us. 

So we’re at anchor south of Contadora, arrived safely and this am I dove and switched the autoprop to the fixed, spare prop. Thanks Bill Rouse and James Cromie!  

Sea-trial this afternoon. 

I’ll report findings. 

Thanks to everyone!!


Porter/Helen Grace and Lilly. 
Ibis
A54-152

Excuse the errors.  
Sent from my IPhone 

On Aug 29, 2018, at 10:27 AM, trifin@... [amelyachtowners] <amelyachtowners@...> wrote:

 

Hi Gang,
I’ve been wondering for most of this summer about the wandering rpm in my D3-110-C motor. I’ve noticed that occasionally the rpm will wander around by 20-40rpm over a period of a second or so. It is obvious to the ear, as well as being shown in the instrument readout, and seems to be particularly prevalent when mooching around in the 1000-1500 rpm range. Haven’t noticed it so much at higher rpm.

I also don’t recall hearing it last year, but we were pretty overloaded with new stuff last year, it’s possible I just didn’t notice it.

Since I’ve now installed a new gearbox, I’ve kind of eliminated any issues on that front (ie pressure drops/shaft brake application)

This year I changed from the original fixed prop to an Autoprop, which is also a new piece of kit to me. Could this be related to the autoprop blades doing something erratic and momentarily loading up the motor?

Do others observe this behaviour? I guess with the trials and tribulations that Porter has gone through this year with his D3-110 we are all paying a bit more attention to this troublesome power plant.

Many thanks
Dean
SY Stella
Amel 54#154
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