HARRISONMIRAGE

There were a lot of guys working through this earlier this year and I'm curious where you all ended up.I kinda got bored with messing with it but ended up with 84 pr/94 sec 6.5 powervalve.It's a 502 10:1 comp, aluminum head,rpm air gap intake,224/234 cam.It's in a 26' 24 degree 5000lb non stepped boat.I was 2 jet sizes up from this and are considering putting it back as I gained no improvement dropping them.My economy is just a hare under 2 miles per US gallon(I'm in Canada so our gallons are bigger).I have no transom soot but it smells rich.The plugs are all over the place but look good in general.To me not fouling and no melted aluminum makes me happy.I don't seem to notice much difference in opperation without making drastic jet changes wich is probably due to the load on the engine.Making 20 more HP in my boat is not noticable so it makes tuning for top speed hard to do.

35/25

You are pretty close to what I have found to be good jetting for these carbs. If anything, you are a bit richer. I had the 800 on a similar 502 to yours in a 271 Formula non-step. It liked 80's in the front and 93's in the back. If you really want to mess with it, you can experiment with staggering the fronts a little. I found this out by doing part throttle runs on the primaries only, the doing plug readings. If you notice that one or two plugs on one side of the motor appear richer than the other side, try staggering by two jets sizes with the smaller jet on the richer side of the motor.... (ie; in my case, instead of 80's on both sides, run an 81 on one side and a 79 on the other). This may seems too small of a change to make a difference, but I have noticed improvements by doing this in some cases.

I currently have these carbs on a pair of HP 500's. I recently rebuilt the motors and did a little port work and installed a slightly larger cam (226/236, 112 lsa). Dialed in the jetting at 82/93. Then, in hindsight, realized I should check the float levels (this should actually be the first step before experimenting with jetting) to make sure they are set correctly. Found that the float levels were too low in both bowls on both carbs. Set them to the correct level (fuel just at the bottom of the sight plug) and noticed that the motors were now running slightly richer. Was then able to go down one size in jetting. Currently 81/92.

Hope this helps.

Rich

blue thunder

I was one from earlier in the year. I've honed in on 81p/92s. Gives a nice tan color. Had other problems that stopped my testing but I was planning to go to 81/90. This is on 456-470cid bored 454s with edelbrock alum rect heads (1.88/2.19) and no port work. Hopefully I will resume tuning shortly

BT

MACDAD260

I'm at 84p, 99s, 4.5pv on a stock Gen V 502 Mag with an Edelbrock Performer RPM dual plane intake with stock exhaust. It runs great with no plug fouling, just a little transom soot and the thru hull pipes have a little soot. No smoke, no smell and 2.3 mpg in a 5000lb boat. I don't know why it likes that much jetting but it stays alive so it's all good to me.

Also have a marine D.U.I ignition, Taylor wires and Champion RV15YC4 plugs.