Caterpillar lag on accelleration

[RickyD]

I have twin Cats 3208s 425 horses. My port engine has a lag zone while accelerating. She idles at about 650. As I accelerate to 1100 rmps she lags back to around 950. As I increase throttle, she comes up fine. I don't think the starboard does this but most of the time I have already turned on the synchronizer, so both engines lag. Last weekend I noticed the port racor vacuum gauge indicated a problem so I changed the filter. No change to the Lag. Any ideas?

P.S. I posted this earlier in the wrong place.

 

[bayview]

Do you see black smoke while this is happening? Will both engines reach rated WOT when run off the sync? Check all the air filters, hosed and clamps. also spin the turbos by hand to see if it spins freely.

 

[High Wire]

Leave the synchronizer off and raise the throttles individually one side at a time, say 500 rpm steps. What happens? Make sure to do it port side first, then start over with starboard side first.


Also did you change the secondary filters too?

 

[RickyD]

Do you see black smoke while this is happening? Will both engines reach rated WOT when run off the sync? Check all the air filters, hosed and clamps. also spin the turbos by hand to see if it spins freely.

I suspected air filters and cable slack. I have not fully investigated all of this yet. I have been "on a mission" and notice how it does this every time but after the lag, it then goes up normally. Kinda feels like slack develops in the cabling. If the Stb engine does it, it is to a much milder degree. It will be a couple weeks before I take the boat out again but I also thought about the air filter. I'll see if I can spin the turbos. Never done it so I'll have to figure it out. Engines start great so air in the lines I think is out, plus I can run for two ours drop the throttle down and when I bring it back up, there is the lag again. No black smoke. Yet I can go WOT though I have not tried it with single engines. The Stb engine has a 50 rpm lower idle speed.