Re: [Amel] Ideal cruising rpm

Danny and Yvonne SIMMS

Hi Duncan, like you I cannot see that it is an engine problem if I could get over 4000 rpm in neutral, and only 2800 in gear and then the sudden self correction. I believe mine was a propellor issue. I had the prop fully overhauled, new bearings, new seals when I was in Newport RI. Was there some friction preventing the autoprop from obtaining ideal pitch that in effect "ran in" and freed up? I don't know. Anything that is less than perfect will prevent the autoprop from acheiving perfect pitch. It is supposed to adjust to rpm, power and load. I would think that any pitting on the prop would be similar to light fouling which we are told to avoid.
SM 299 Ocean Pearl
New Zealand 

From: Duncan <>
Sent: Saturday, 7 April 2012 2:12 AM
Subject: RE: [Amel] Ideal cruising rpm

Hi Danny,

In explaining my problem on Dreamtime II I failed to mention that on the second time I took the boat out for trials the rpm’s did ‘mysteriously’ jump up to 3000 in gear when I throttled up trying to get her to move out of the 1800 range. The speed picked up to a little over 8k, but I recall I was into the wind and some choppy seas. It has never responded that way again and I have been out sailing and using the motor for a month.

Could it be that the prop changes will just not adjust and acts as a drag on the engine. From comments it may be that engine failure is a result of attempting to make the prop respond and the drag is stressing the drive. I’m no mechanic but something is just not right between the transmission and the thrust coming off the prop. The engine is fine with no load. I have looked at the engine and the brake and it does not appear that the shaft is not spinning properly.

All this said, it seems that there is little need to ask the engine to run at over 1800 +/- for the fuel consumption is good and the seed in average seas and wind age is around 7 k/h. The problem I have right now is I need more power maneuvering the boat and when you ask for maximum thrust you want it right then, not after the boat has gained hull speed. I also see the need for RPM’s for the cleaning of the exhaust. I suppose one could go to neutral and blow it out.

From: [] On Behalf Of Danny and Yvonne SIMMS
Sent: Friday, April 06, 2012 12:17 AM
Subject: Re: [Amel] Ideal cruising rpm

Hi Barry, we cruise at 2000 rpm generally. At 6 knots you cover the ground well. We had the rpm problems that some seem to have with the TMD 22, 2800rpm max in gear but cheerfully running up to over 4000rpm in neutral. Ours self corrected suddenly when we were in Tahiti, now will achieve 3700rpm under power. Hasn't changed my cruising rpm though, still believe 2000 a good speed. Higher revs seems to increase the fuel consumption expotentially.
SM 299 Ocean Pearl
New Zealand

From: Barry < <> >
To: <>
Sent: Friday, 6 April 2012 11:30 AM
Subject: [Amel] Ideal cruising rpm

Recently, I serviced our turbo on our TMD22-A only to find it was badly carboned up and the turbo boost relief valve had seized closed. We have replaced the injectors and a new Garret turbocharger. Needless to say the engine is running very smooth now however, I was wondering what rpm other owners are cruising at under power alone. In the past we have been cruising at 6 knots at 1900rpm with a clean bottom. Those of you who have a similar engine, what economical speed do you find best?

Best regards
Barry & Robyn
Tradewinds III SM 171

[Non-text portions of this message have been removed]

Join to automatically receive all group messages.