Official Cummins 6cta 450C thread

Thanks, I'm listening to this with a preventative ear......Sounds like that fitting was installed on a Friday afternoon.
 
Ha! Probably true. This boat has been great. But you gotta look for stuff to be wrong on a regular basis. Then fix it before it's an issue. I guess that's all boats. Fuel fittings have been this boats thing. In addition to the two leaky supply fittings I mentioned, I had the port engine injector return line crack at its little banjo fitting twice in two years. They are about $180 from Cummins. I keep one onboard as a spare now. I probably had it's idle too low or something causing extra vibration.
 
I started there but wasn't smooth enough. I cranked it up until it smoothed out. I'm at 650. A knowledgeable poster here has his at 675. Another has his at 625.
I think the engine performance sheet I have somewhere listed it as minimum idle rpm 600.
 
675 for me really smoothed it out.

Ok, so is it normal for them to be a little rough and vibrate at low rpm? My port is a little rough at idle, my starboard is not. I was thinking it might just be idle speed, because I add a hair of throttle to get 100rpm or so and it does smooth out. So this is probably normal?
 
Yes but you should adjust the idle so that doesn’t happen.
 
Same issue on my port. Is this a quick and easy adjustment? Also how does adjusting one affect your engine synchronizer?
 
I got some new digital tachs as a gift. I hooked up the new tach in parallel to the existing port tach. Was surprised. Current analog tach is on left. Digital tach is on right

700 725
900 957
1100 1178
2000 2105

Now to do the starboard side. Based on this I have been turning 2300 rpm or so when cruising at 2200. And my WOT is most likely well over 2700. Here is a picture with the analog tach at 1100.
 

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I got some new digital tachs as a gift. I hooked up the new tach in parallel to the existing port tach. Was surprised. Current analog tach is on left. Digital tach is on right

700 725
900 957
1100 1178
2000 2105

Now to do the starboard side. Based on this I have been turning 2300 rpm or so when cruising at 2200. And my WOT is most likely well over 2700. Here is a picture with the analog tach at 1100.
Do the tachs have a pulse count adjustment? Do you have an optical RPM reader to verify this is what the engine is truly running?
 
Same issue on my port. Is this a quick and easy adjustment? Also how does adjusting one affect your engine synchronizer?

Do the tachs have a pulse count adjustment? Do you have an optical RPM reader to verify this is what the engine is truly running?

Great questions guys. Looking forward to answers.
 
Do the tachs have a pulse count adjustment? Do you have an optical RPM reader to verify this is what the engine is truly running?
I have no idea the answer to these questions. I do know all the experts here (FrankW, My3sons, etc) and Aetna tell me these are precise and reflect exactly what the engines are turning. Hopefully one of them will follow this up as to why it's true. I did have to set some dip switches to match the engines
 
I have no idea the answer to these questions. I do know all the experts here (FrankW, My3sons, etc) and Aetna tell me these are precise and reflect exactly what the engines are turning. Hopefully one of them will follow this up as to why it's true. I did have to set some dip switches to match the engines

Looking on Aetna's website, I found the DIP Switch guide. I don't know if the flywheel is 127, 138 or 158 tooth count

https://www.aetnaengineering.com/wp-content/uploads/2016/01/PPR-Engine-Applications2012.pdf

https://www.sbmar.com/articles/beede-tach-settings-cummins-flywheel-tooth-count/
 

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Dip switch on tach is set for 127.
Yup. I just looked up the flywheel on quickserve, says its a 127

Very interesting on the RPM difference. How is the fit in the dash panel? I'm definitely considering those tachs too......
 
Our engines are mechanical so as long as the flywheel selection is correct they will be spot on.
 
T
Same issue on my port. Is this a quick and easy adjustment? Also how does adjusting one affect your engine synchronizer?

Adjusting the idle doesn’t effect the sync.
The sync gauge is wired right to the tachs, it reads the same pulses as the tachs do but because it is what it is, an analog type gauge, it can be inaccurate just like the tachs can be. At certain rpm ranges I can see my sync gauge not quite centered when the aetnas are exactly the same.
I don’t have engine synchronizers on my boat but the way I understand it is the glendennings work the same, they receive rpm info from the motors and sync the slave to the master accordingly.
Changing the idle doesn’t effect it.

The idle is easy to adjust, but might not be quick if it’s a bear to reach. Also it is very sensitive, hardly a bit of a turn can change the rpm 10 or 20, then setting the lock nut usually changes it, requiring a few attempts.
 

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