So, we have been having engine trouble, sometimes the engine gets bogged down when towing someone and slow to respond. Not consistenlty, the engines just seems under a bigger load sometimes than others. Nothing has changed, like weight or number of people. <BR> <BR>The boat is 2001 Supra w/5.7 330hp indmar w/ 159hrs. Never done anything except oil changes and impeller change. <BR> <BR>So is this a maintenance issue spark plugs, timing etc? Or do I have bigger or other problems?

carbed?

No injected "MPI"

replace the water/fuel separator; could be clogged and its an easy thing to eliminate as a possibility

If you haven't lately, change your fuel filter and check / clean the pickup screen.

What is the pickup screen? <BR> <BR>Is there a fuel filter and a water/fuel separator?

Not all boats have water separators, which usually look like big spin-on oil filters. The pickup screen is in the gas tank, on the end of the pickup tube.

Could have also just gotten some bad gas.

So, at this point it should not need to have a "tune-up" so to speak? Just check the filter and maybe run the gas out...

Your description sounds like fuel starvation or maybe bad gas to me. A "tune-up" on an EFI motor doesn't encompass much, these days - change the fluids, fuel filter, and maybe the spark plugs.

sounds like fuel filter: trace the line from the tank. look for a fuel/water separator too

The fuel/water separator is probably at the front of the engine (nearest the transom) on the port side. As someone said, it looks like a large spin-on oil filter. It's not too hard to access, but you may need an oil filter wrench to remove it. <BR> <BR>I think it also serves as the fuel filter, as I have not found any other fuel filter on my Supra.

Thanks, I'll check the fuel/water separator.