Help - HP500 Backfire - Brand new
 

I finally got my 47 fountain in the water and the 500 efis seem fine at idle but the starboard wants to back fire when under load. Seems fine at idle bt when trying to get on plane it back fires. it seems like its comming from the air intake as it is a crack sound almost mechanical in nature. this engine is brand new - 0 - hours I did keep moving the engine up and down in neutral to start the break in process. but other than that I have not broken it in yet. the popping started at about 2000 rpm and is intermittant not constant. I shut it off and idled home and started it at home and it still seems fine with no load reving out of gear.

Help, I am going out to look at it now. I do have a scan tool.

Thanks

Re: Help - HP500 Backfire - Brand new
 

Ray,

Sounds like a lean condition. If it is something mechanical, like a rounded cam lobe or mis-adjusted lifter it should backfire in neutral as well. Is the fuel pressure good?

Re: Help - HP500 Backfire - Brand new
 

I agree, sounds like a lean mixture.

Re: Help - HP500 Backfire - Brand new
 

Raypanic--If it's not leaning out, you may want to make sure the timing is advacing

Re: Help - HP500 Backfire - Brand new
 

Here is what I have so far, I hooked up the scan tool. no codes everything looks good at idle. I tested all three engines, the only things different are the IAC values:

SBD Engine (Bad one) BASE - 15 POS - 15
PORT Engine BASE - 40 POS - 38
CENTER Engine BASE - 5 POS - 5

Not sure if this means anything but It's the only thing that vaies from engine to engine. I am contacting a dealer to see if they can help.