OMC 2.5 loses power at full throttle?

85 120 hp 2.5 gm omc
Let me start by saying The carb. was rebuilt last year and new fuel filters.
Today was the first time this boat touched water sense august. No problems last year. and was winterized. Fast froward to today For the first 15 maybe 20 minutes, all was good. then sudden power loss at about 2800 rpm. It kind of felt like it was either not getting enough fuel or to much.....Hard to tell. I backed off the throttle and she ran sound. I quickly turned the other way and limped back to shore. I also would hear a slight pinging when trying to get up on the plane. What dose this sound like to you guys? Thanks

Re: OMC 2.5 loses power at full throttle?

You're most likely leaning out at full throttle. Ensure your carb linkage is adjusted correctly (butterflys reach vertical when throttle lever is full tilt). Who rebuilt the carb? You may havew a plugged jet or restricted needle and seat.

As for the pinging... What octane do you run? What is your initial and total timing, and at what RPM? If you have too much total timing it could certainly hurt your WOT performance, and if you're pinging under load you're looking at some potentially bad things like broken rings, cracked pistons, galled bores, and that's just scratching the surface of waht mild predetonation can do.

Re: OMC 2.5 loses power at full throttle?

it sounds like a plugged fuel filter or bad/stale fuel.
did winterizing include stabil?
was the fuel already stale when the stabil went in?

other things to check:

flame arrester clean?
antisiphon valve at fuel tank
fuel tank vent taped off or plugged with mud from wasps
fuel pump
fuel line collapsing inside

Re: OMC 2.5 loses power at full throttle?

Ok everything howard said. Plus clean all the filters again, check the carb again for no clogged jets.

Have someone on the boat with you to adjust the timing, to hit the sweet spot they drive you adjust.

Ok if all else fails try unplugging the esa module. And the overstroke switch.

Then try it again, when the esa goes alot of weird things can happen.

You know where the plugs are. They are on the starboard side held together with spring clips. Not the fuses, be careful know where they are before you go on the water.

Do not pull the fusses.

Re: OMC 2.5 loses power at full throttle?

ok sounds good, Sone as It stops raining I'm going to swap out the fuel pump and check fuel lines, clean spark arrester, But I've never delt with a antisiphon before, how could I tell if it's shot?

Re: OMC 2.5 loses power at full throttle?

I had the same exact motor, clean the fuel filter at the fitting to the carb, The fuel filter in the fuel pump, no need to change it out, the pump or filter.

Follow the fuel line to the top of the inline fuel tank, the fitting at the tank is the anti-syphon valve. Take it off and blow thru it see how much pressure it needs to open, don't need alot and check if it's dirty.

What i think happened is that you have old fuel in the tank with alot of gunk in it. The gunk may have clogged your carb and filters. You have a fuel water separator? Dump the filter into a clean jar see what comes out.

After you take off the valve at the tank check to see if the fuel pickup tube in the tank has crud on the bottom screen.

Maybe you can pump out the garbage on the bottom of the tank with a hose hooked to a cheap dc fuel pump hooked to 4 feet of hose and into the back of the tank with that end.. Other end into a clean clear jar, so when you start pumping clean fuel you can stop pumping.

The vent blow into the tube from the transom side if theres is no clog you will know.

Then follow the other post, and post what happens.

Good luck !

Re: OMC 2.5 loses power at full throttle?

Sorry I did not reply earlier but better late than never. ha-ha. I Installed a new fuel pump, new fuel filter, new fuel line, new anti siphon valve, cleaned the spark arrester, new plugs, new points & condenser. But the problem the whole time was a bad spark plug. Can you believe it. Well anyways she ran great for about 3 trips, now I've got a carb problem again. When I'm at a complete stop with the engine idling then floor it to pull my heavy friend up on the wake board the motor hesitates, like a low end flat spot."I will buy a new carb this time"
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