3116ta rpm question

[margarita jane]

Went for a run today before haul out and tryed full throttle run...boat was lightly loaded (1/8 fuel + 1/4 water) and had a slimey bottom yet engines wound up to 3050(Aetna digital tachs) and was still climbing higher when I backed off, not expecting to see that hi RPM. Expected to see just a little over the 2800 RPM @ WOT.(was remembering the 3050 or so no load RPM figures) Unusual or am I just being paranoid?

 

[osd9]

Was that your first WOT run since you put on the Aetna Digital Tachs?

 

[Mr Salt]

Caterpillar rates the engine at 2,800 rpm and therefore would be governed at that speed. It sounds to me like the the tachs are not calibrated correctly. With a slimly bottom I would expect that the engines would not be able to wind up to the rated WOT and certainly not greater than that.

Mr Salt
Caterpillar C-12s
2001 540 CPMY
Cape May, NJ

 

[fc3]

Depends on how light you were. You were at least a ton light of fuel and water. Load the boat to your normal weight (passengers and their "stuff" too) before you begin any diagnostic work.

Best regards,
Frank

 

[osd9]

Caterpillar rates the engine at 2,800 rpm and therefore would be governed at that speed. ......

2800 rpm is the (minimum) fully loaded WOT rating. They are governed at the bare idle speed which is somewhere in the 3100 rpm range.

You need to get a hold of an optic laser tach and see if your tachs are calibrated.

It's not uncommon, and actually recommended, that you prop to spin slightly over the rated fully loaded WOT rpm. However, I would think that 3050 and rising, is a little over slightly over.

So long as you hold back on the throttles, you aren't doing any harm to the motors. The worst case here may just be that you are underpropped and losing speed.

Did you check your bare idle rpm at the dock?

 

[margarita jane]

yes, was first WOT run since tachs installed, agree, need to have tachs calibrated, however will have to wait til spring as boat was put in heated storage today and yes WAY to early.... thanks for advice.... Tom

 

[osd9]

OK.....it was the first WOT run with the Aetna tachs.

Now, you don't say, but, were both tachs reading the same values (or close enough). If so, then I would tend to think that the RPMs you were seeing on the Aetnas were real. It would be unlikely that both Aetna tachs would be out of calibration by the same factor. Everyone I've talked with, including the owner of the company, agree that they are pretty close to dead-on straight out of the box.....I know that mine were.

You may very likely have been underpropped all along and just didn't know it.....which is acutally a good thing as far as the life of the motors is concerned.

A simple test with an optical tach next season should give you some quick answers.

 

[margarita jane]

both tachs were within 10 or 12 RPM and synch gauge was dead on

 

[steviep53]

Re: Angelling

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This guy has been busy spamming a ton of topics...