had a power valve go bad due to backfire,purchased part from holley to correct the issue,no problems since

The choke linkage comes up thru the carbs air cleaner base. You sure the Flame Arrestor is not interfering with it somehow ?

And how tall is your flame arrestor ? It might be too short. Also did you clean it very well. Hold up to the sun can you see daylight thru it ?

Just a quick update....motor ran good on other arrester and the just cleaned one. Going to drop it in the water today and give it the real test.

It's the stock 500 arrestor. I could see light through it but apparently that can be deceiving. Gave it a better cleaning and although it didn't look much better to me, it's holding good idle and is responsive now. Not thoroughly confident yet but I'll run it and find out if it's a fluke or not

Ok so I got to run it and the results kinda got me nervous. Started and warmed up great. Did a 3 mile run no hiccups. Shut it down to take a look and found a pool of oil sitting on the intake manifolds. Checked oil level and cleaned up the oil. I'd say it was about 1/2 a quart. Ran it again for a short distance and no oil, ran some more and no oil. Only thing I'm noticing now is a whistling at idle that comes and goes. Totally gone when put in gear. Any ideas? Only my 3rd time out with this new to me boat and I'm starting to panic

HP500's have PCV valves. They are just to the rear of the carb, stuck right into the intake manifold. See if this is working correctly.

#1 thru #5 in pic below.

Thanks! Your the 3rd person to suggest that. I'll look at it in the morning when I get out of work. I'm hoping that's all it is

While you are there, pull out Valve (#4) and look thru grommet (#5) and see if you can see if the metal shield (#33) is there. For some reason, some people don't see the need to replace this when rebuilding or redoing top end. This valley tray keeps oil from being thrown onto the bottom of the intake. Why this is important with the HP500 and some others that have the PCV in thru the bottom of the intake, is so that oil doesn't get thrown up into the PCV. If it does, it can fill the pcv and pcv hose enough that the engine 'uses' more oil - or in this case - inhales oil. ie; oil goes back into carb and thus down intake, head, comb chamber, and etc.

Is the pcv under the distributor cap? I'm looking at pics of my motor and I don't see it. I've tried to post a pic but can't seem to from my phone. Also I've noticed from pics of other motors that both valve covers have vent lines to the flame arrester and mine only have one, the other cover has like a small breather filter. After looking at pics of where it's supposed to be, I definitely don't have pcv valves. I'll attempt to post pics again