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Old 12-11-2019, 09:18 AM   #10
smitty477
Guru
 
City: Northport
Join Date: Aug 2015
Posts: 2,046
Quote:
Originally Posted by Baker View Post
The tachs are not accurate. I dont sync to the tachs...I sync it by ear....wah wah wah waaaaaaaaaaaaahhhhhh. Well aware of Aetna digital tachs as I have them on my current boat. Likely the first mod I will do on this boat. I will have to redo my panel though as the tachs are huge on this boat so I would need something to fill that hole. Anyway, maybe digital tachs and some tension adjustment might be all I need. I can sync my current boat and it will stay that way all day if I let it. I honestly think there are some other harmonics going on with this boat that might make it sound out of sync when maybe it isn't.

As far as syncing by boost....no way. 50rpm difference would be maddening. My current boat I am always within +/- 5rpm. I don't know what kind of boost gauges you have but my tachs are significantly more accurate than my boost gauges. Boost gauges should be a reference to the health of the engine(like oil pressure)....and not a primary source for setting power....that is strictly my opinion.
I have many examples but here is one with the Cummins 6c's....
Cruising from Northport to Mystic one summer with a friend who had a 46 Sea Ray with the 450 6C Cummins.
He was on sync and at about the 4 hr mark his port side engine began to black smoke pretty bad.
We slowed for the rest of the trip and when in port we eventually found a slit in his flex hose between the turbo and intercooler.
So that engine gradually lost rpm and the sync age was making up fuel to match the rpm's.

"I don't know what kind of boost gauges you have but my tachs are significantly more accurate than my boost gauges."
Your tachs tell you nothing about the load on the engines - the most important thing you can know.
Any variation in props as tuned, growth on the props or anything you pick up along the way will unbalance the load between the engines.
The engine which becomes overloaded will be subject to damage much sooner then you might think.

"and not a primary source for setting power"
You cannot set power with a tach especially on a twin engine application - if you have ever down that you likely know from the unbalanced fuel usage.

FWIW - I really liked the Cummins 6c's in our friends boat , a great engine.
Things to check are the typical aftercooler maintenance, aftercooler leaks/cracks at the bottom zinc ,and the bottom turbo coolant banjo bolt for leaks. Pretty minor know issues for that engine IMHO.
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