endeavor, here is my thread from last year, where it is stated that the 800 cfm (list 9022) is what is used for the HP500. I haven't contacted Merc myself to confirm, but I have a couple of friends running the HP500's, and they both said they are 800's. I'm pretty sure that is accurate. Hope it helps.

"A 9022 list 800 (which is what a HP500 carb is) comes with a 72 in the primary, an 87 in the secondary, and a 6.5 PV in the primary side only." Keep in mind that Merc ran the staggered jetting to try to even out fuel distribution with the single plane Dart intakes that the HP500 employs.

http://www.offshoreonly.com/forums/g...ley-800-a.html

HP500 Carbs are 800cfm...for sure... and are the #9022's as posted.

OK- Good to put that to rest! Thanks guys!

Hey Endeavor, what did you end up settling on with your jetting? I am going to drop down a few sizes on mine, at least on the primary side. Also need to check the float level. With the 100* air temps two weeks ago, the exhaust fumes would make your eyes water. Way rich - pulled the plugs last week and they are black and soot-covered. Definitely too rich.

Let me know what you came up with.

I'm trying 75 Primary and 89 Secondary. I'm not in the water yet, I've been fighting water in the oil and finally found out it was coming from a leaking valve guide. I'm in the act of dealing with the machine shop as I type. I'll post on the jetting as soon as the boat his the water!

That's a bummer. Hope they get it resolved quickly so you can get back in the water. I'm fighting starter issues on mine today.

Just an update for anyone jetting a new build. The jetting that I posted earlier is what I'm still running. This is 75 primary and 89 Secondary. From what I can tell the jetting seems spot on. So for the record the build was stock Merc 454 Mag/420 bottom end, stock 088 heads; edelbrock RPM intake; Roller cam: 232/237, .579/.579 lift @ 110; Exhaust is Gil through transom dry to the tip. I'm quite happy with the results which is right around 440 hp. I have a bit more that I can squeeze out of it as I'm not yet at the proper RPM's but I'm waiting for winter to have the props worked on.

What brand of cam is it that you are running, and what kind of roller lifters? I'm shopping around for a different cam while mine is out.

It's a Reeds cam, I bought them from mild thunder. The specs are very close to that of a 500 EFI. Reed Cams is no longer in business but from what I've seen out of my engine they made a good cam. The lifters are Morel and the springs are Isky SP-8005.

I'm running the same springs in my 489. Where did you buy your Morel's? I would like to upgrade to a set, but it's tough to swallow the $650 price tag for a set. :eek:

I came across a member selling one of Bob M's rollers for a decent price, but it was set up for a 502 running AFR 305 cc heads. I'm not sure if that would be very much optimized for my setup, considering that I am running stock 088 heads with some minor bowl blending and 2.25 intakes. Also considering a ZZ502 cam and just keeping my stock GM lifters, but the lift is kind of wimpy. Hmmm, I feel another cam selection thread coming on... ;)