Built 9.7 comp 540's from 500EFI's . Injectors had been upgraded to accomadate Prochargers that we were removing. Turns out 2 of the injectors fired up to about 3/4 throttle but would shut down at WOT. These 2 cylinders recieved NO fuel and detonated and blew the pistons apart with 2 hours of running the new motors. Once we rebuilt that one test runs showed the 3 month old ETHANOL fuel had deteriorated to the point is was NOT 93 anymore.

As stated above, the failure of the motor was technically my fault. Bad injectors, bad fuel. A stock 500EFI that has been put together properly should run 5,000 rpms until you run out of gas with no issues.

BTW: The knock sensor is what alerted us to the fuel problem after rebuilding the motor, I had the computer programer here on the boat for test runs once we had it back together.

If this is not your area of expertise, ask why? Rather than say you doubt it. Yes, little fuel to will burn pistons, and very quickly!

Sold a guy a motor 2 years ago and it ended up blowing up recently.
They tried to blame me, # 2 rod bearing had failed.
I used my fiberoptic borescope and found out that the piston expanded due to high heat and that was why the bearing damage occurred. Motor either leaned out or simply had not enough water flow. I showed his mechanic the inside of the cylinder and the up and down lines from the piston grabbing the cylinder wall. Turns out that the marina did not install the raw water pump I gave them with the 4 " pulley, and ran the 6" one that was in the boat that was underdriving the pump, as well as not installing the thru hull fitting and strainer. I don't know how to deal with this, I like these guys , and I haven't been able to proove very much to them because everything gets screwed up. This motor was 9.4 - 1 and also needed 93 octane.
The owner of the yard is pissed because I can't be there and I did not do the installation , or even be there to overlook any potential reasons for my beautiful motor to go bad.
I'm going there in the am and need to prepare myself for whatever BS I may encounter. Thanks, BBB

No fuel wouldn't burn a piston, but a injector that supplied fuel until 3/4 open definately would as it would lean out,Smitty

absolutely right

I sent all 16 injectors to be tested and marked then for MY reference only. The tester was able to tell me which 2 pistons were ruined after testing them. (I never told him which cylinders or in which motor the problem occured)

Just to respectfully disagree again, in a boat with open exhaust it's very hard, if not impossible, to hear if an engine is detonating. All the electronic safeties on the EFI motors are great but what about a carb motor? No knock sensor, no electronic fuel injectors just an antiquated fuel metering device called a carburetor. Change fuel filters as much as you want, some trash will still get into the bowls. One small piece of trash in a jet can lean it out and wipe out a couple pistons - and in a boat, under constant load, it won't take long. Or, here's another for you. How about your timing advance module takes a sheet while you're on the water. You could have put a timing light on it right before you left the dock but it still may take a dump while underway. Had it happen to a friend of mine. In one particular range of RPM the timing would begin jumping back and forth erratically and would sometimes stick in a far advanced position. Found the problem after it wiped out some internal parts. So, yes, most things can be prevented by keeping track of your rig and performing the required maintenance. But, parts do fail and sometimes you can't foresee the problem.

Just My .02

500efi's are generally tough as nails. I put 414 hrs on mine before pulling it ( bottom end ) apart. NOT easy hours either. I have run the boat 30 miles at 5200rpm on several occasions, dozens of WOT poker runs and generally toture tested the sucker all on 87 octane and never hurt the bottom end. Just wore it out.

I melted two last year due to a bad knock sensor.

Who did you send the injectors to Russ? I need to get mine in the mail.