I had the port engine rebuilt over the winter. It's a 500 efi, and when I take it up over 4000 rpms it will top out at 4500-4600 then start losing rpms. I can back it down below 4000 for a few seconds then take it back up and it does it again. I have changed the fuel water seperator filters. Just looking for suggestions where to go next. I will probably hook a fuel; pressure gauge up next to see what pressure I get.

Check fuel pressure. That is most likely the problem. Be careful, if it is pulling RPM it is because it is detonating!!

i agree sounds like a fuel problem 4 sure

Have You Changed The Silver Filter At The Top Rear Of The Motor?

Also is the other motor only going to 4600? if so you need to buz it higher after you find the problem.Its Proped wrong.

Rob

Last year they would run up to 5000+. So it's something that has happened since the rebuild.

So both motors are not turning up???

Is all the fuel system stock 500efi stuff???

I had the same problem last year with a 525efi.
There is a sensor assy on the crankshaft pulley mine was part #828358 2.
I would run wide open then it felt like I was rumming out of gas. I'd slow down for a while then it would be ok. It happened twice on poker runs.
Changed the sensors and never had the problem again

Steve

Oh ya I changed those filters first--- still did it !

Steve the 500efi doesnt have a crank trigger like yours.