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Loss of RPMbs

delacova

New member
"I have twin detroits 6-71&#39

"I have twin detroits 6-71's 485hp. Lately I have been having a problem with my stbd engine losing RPMs. Ran all day yesterday at 1100 rpms on a fishing trip. As I got closer to home, I went up to 1700. a short whilce later, the STBD engine droped to 950 rpms and reved back up passed the 1700 mark to about 1850 then lowered back to the 1700. this problem has been going on from time to time, not always, However, yesterday it happend quite a bit, I had to keep it at 1100 rpms the rest of the way. Any help as to what may be causing this drop in rpms will be greatly appreciated."
 
"IS THERE ENY SMOKING WHEN THI

"IS THERE ENY SMOKING WHEN THIS HAPPENS ? CHECK THE AIR SHUTDOWN LEVER ON THE OUT SIDE OF THE BLOWER HSG, IT SHOULD NOT HAVE ANY MOVEMENT. ALSO CHECK FUEL PRESSURE."
 
"Marvin, Thank you for your r

"Marvin, Thank you for your response. Yes, there is black smoke when this happens. I was also told to check the Racor primary filter which should have 30 micron filters. I have the 2020TM filters. Do you think the micron on the filters is critical and I should have the 30? Also what is the significance of the black smoke? Thank you for your input.
Rene"
 
MICRON OF FILTER IS BETTER. BL

MICRON OF FILTER IS BETTER. BLACK SMOKE IS CAUSED FROM LACK OF AIR OR OVER FUELING.AIR= AIR SHUTDOWN HSG/AIR SILENCER.
 
"Marvin, THank you for your re

"Marvin, THank you for your response, we found the cause of the black smoke to be a broken exhaust manifold. 4 of the ear-like tabs on the manifold had broken off. I was lucky to find a new replacement manifold from Covington who advised that they probably had the last one on the East Coast Thanks again for your help."
 
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