My boat has twin Cummins. We took...

[BB_LEE]

My boat has twin Cummins.  We took our first ride of the season and although operating smoothly, one engine ran 150 rpms less than the other and was using 1.5 gph more.  Does this seem to be within tolerances? I have been told that since the engines are running well that the tach is probably the issue.  Is the digital tach running off of the analog tach?

Also, after running for a couple of hours and then coming down to idle speed, my port transmission makes a scraping noise.  When the gear shift is put in neutral and then reverse, the noise goes away.  It will not occur again unless we take another extended ride.

Any one experience these issues and do yo have any ideas.

Thanks

[lady_Patricia]

What year is your boat?

[runman]

On the RPM issue I would first change my secondary fuel filters (on the engine)

[SMT]

Fuel filters probably large portion of problem. Lower rpm and grinding transmission could be a larger problem as you are using more fuel. Check dipstick for metal shavings.

[BB_LEE]

Hi everyone
It is a 2007
All fuel filters have changed during commissioning a week or so ago.
I have to check if they did an engine and transmission analysis this year
Did it last year and all was good
Thanks for the feedback

[BB_LEE]

One other thing....the engine using more fuel is the starboard and tranny noise is port

[Bob_440_DA_w_Ca]

Before you tear into too much, buy a hand held photos tach. Many on line for cheap. And confirm the tach accuracy. They can be notoriously bad. Transmission noise is another issue. Get an oil sample analysis done soon.