I just recently have begun experiencing a problem with my 1988 5.7L Mercruiser Stern-drive bogging down. The problem seems to occur at any throttle position, and I've experienced it immediately upon a fresh start and also after an hour or so of use. It seems a lot like the engine is being starved of fuel. Generally when this situation occurs if I set the engine to idle, it will sputter and stall out. After a difficult restart (have to put throttle in full open position) the engine would continue to run very poorly and surge power in and out. Generally after about 10 - 15 mins it will recover and run at full power with no trouble for the rest of its operation.<br /><br />This problem has only occurred since my last fill-up, and seems to be getting worse each time the boat is run. I have not filled up my tank since, and my tank is now 1/4 full.<br /><br />My first suspicion is the fuel itself, though I had added dry gas in hopes of removing any fuel contaminated by water. I have checked the choke and that seems to have free movement and no obvious obstructions. The fuel lines seem solid with no obvious leaks, and I will replace the fuel filter next.<br /><br />In the meantime though, I am wondering, based upon these symptoms, if anybody can suggest the most likely problem? Is this sort of behavior at all consistent with a clogged filter? bad gas? Where else might I look next?<br /><br />Thanks for the help..
It does sound like a water in fuel issue to me. Do you have a water separating fuel filter? Looks like an oil filter. If you do, remove it and look to see if water is present. Check the filter screen at the carb connection. If you don't have a separator, it will probably necessary to siphon the remaining fuel from the tank......J