Hello, <br />I've read many of the responces to questions and you guys really seem to know your stuff. I only wish my repair shop did. <br />Q: I have a 1999 Cobalt 206 powered by a V5.0 GI DP. It has had yearly recomended service and last week had a tune up that included replacing the plugs and checking the timing, compression, fuel pumps, props ect. My problem is: Over the last few times it's been in the water it has continously lost rpm and speed. The engine runs perfectly under idle and with 1/4 throttle, but when I give it more throttle it sounds as if it's sucking air. It's injected, but sounds like a big 4 bbl carb opened wide. I can rev the rpms to the 4000 and the motor sounds great and runs normal in nuetral, but in gear and any more than 1/4 throttle under a load it DOGS. It will only get to about 3000 rpm under load, and just will hit 30mph. (when it's running right 57mph was no problem) My mechanic (Cobalt Dealer) checked the fuel pumps but only while in nuetral. Could it not be getting enough spark under compression? Or is there another way to check the fuel delivery system to confirm that it's getting enough fuel when in gear and under load? I paid the mechanic for his diagnosis but I'm still "in the same boat" pardon the pun. Please help!
<br /><br />The most comon problem with a marine driveability issue,is fuel system problems. Followed by poor secondary ignition system conditions. Then the primary electrical ckt.<br /><br />Exhaust restrictions that cause power loss conditions can occure but are rare. <br /><br />Typically a restricted exhaust system would cause an engine to run hotter than normal because the water cannot exit the engine in sufficient amounts. Engine cooling water exits engine thru the exhaust system. It keeps rubber componants from melting.<br /><br />If it has ever been run hot enough to burn/melt rubber componants "MAAAYYBE" its restricted. I doubt it.