Popping Noise at W.O.T

[Spencer Allen]

Hello -

Looking for some guidance on troubleshooting my boat - 2015 Chaparral, 4.3 Mercrusier EFI, 74 hours on engine.

Recently starting getting a random popping noise under WOT along with some loss of power. Everything runs great up until I hit 38+ m.p.h then it starts to bog down like its starving for fuel once I back off throttle everything returns to normal. I have replaced fuel/water filter, plugs, tested plug wires, drained fuel, treated and refilled, with no luck.

Not sure what to check out next, any guidance would be much appreciated.

Thanks

 

[Scott Danforth]

Lean sneeze is my first thought. Youre running out of fuel

 

[Rick Stephens]

Lean. Time to run some injector cleaner, change filters. Running lean will turn pistons into dust.

 

[tacx]

Just a thought here, but will a plugged fuel tank vent on an inboard act the same as an outboard?

 

[Scott06]

Yes plugges tank can do it as well need to check anything that will interfere with fuel delivery those aboveboard are most obvious run with tank in capped and see if it makes a difference

 

[Spencer Allen]

Thanks for the tips guys, going to clean the fuel injectors and check the vent lines this evening hopefully that will get me back running right before the weekend.

 

[kenny nunez]

Have you had the fuel pressure checked? Also try the separate fuel tank way with a 6 gallon out board tank to narrow down the cause. Some fuel tank suction tubes have a small funnel shaped screen inside of them that also could be the problem. I have removed them and they had what looked like tiny hair strands in them.

 

[tacx]

SA, Please let us know what you find.

 

[Spencer Allen]

Cleaned fuel injectors, checked fuel pressure and vent lines (both were fine) today just got back from lake. The popping noises seems to be gone but still hesitating and sputtering at WOT and doesn't want to go above 39 mph or 4000 rpm. Once I back off throttle everything goes back to normal...

 

[muc]

Did you test fuel pressure at high RPMs?
If you post engine serial number, might be able to help.

 

[Spencer Allen]

No didn't check pressure at high rpm, only at idle.

SN# 2A193964

 

[TurtleTamer]

You have to check it at high rpm where the problem is happening. Pumps don't always fail completely bad. They can get weak as well.

 

[muc]

Need to test pressure at the RPM that the problem is happening.
Did you dump the gas that was in the filter into something clear so you could check for water when you changed it?
How did you drain the gas tank?
How does your distributor cap look? They are known to have issues like your experiencing.