Engine Issue - Lack of Power

[Tkenopic]

Hi there,
My new-to-me A4 has been working well this spring. Last night I took a few other friends out with identical boats/A4's (C&C 30) and they were remarking how slow the boat was. I increased the throttle, but the power did not increase. We sailed for the evening, came back to the dock, everything was the same. Today when I went down, the engine definitely sounded different, like it wanted to stall, but wasn't. Once we put it in gear, there was a noticeable drop in power even from last night. Increasing throttle does nothing. We nursed it back to the dock, so I could do some investigating. I have good spark on all 4 plugs, good compression on all 4 cylinders.

I'm wondering what your diagnostic sequence would be to try to determine the problem and any likely causes that I could try fixing?
Thanks,
Trevor

[Al Schober]

First thing to check would be your propeller. Sound like it's fouled or has something wrapped on the blades.

[edwardc]

I concur. Several seasons ago, I had similar symptoms. Upon haulout, I discovered a short loop of line caught on the prop.

[Dave Neptune]

Do check the prop however the first thing I would do is see if the choke helps while under power. Just apply the choke slowly and if the performance improves it just may well be in the carb. This is an easy and quick check. You can even do it against the dock lines.

Dave Neptune