Need help with my gas hog(boat)
 

Let me start by saying, i have no issue feeding it,just seems a little excessive.
I have a 20 ski brendella comp boat. was bought with a cracked block. Had a customer back out of a engine deal and bought his motor.its a .30 over 350. compression ratio specs out to be just under 10.23-1. Iron eagle heads with stainless 202 &160 valves, Cam is a 383 fastburn roller from Gm and i believe is 510 on intake &547 on exhaust. Carb is a 725 Marine from a 460 ford which was used by omc. it has 92 primary jets and 88 on the seconderies. plugs look awesome color just a tad to medium brown. Motor runs flawless all day long. but seems to like the gas station more then i think it should. not in any way complaining. but looking for a honest feedback. it will burn a 22 gallon tank pulling the kids around on a tube in about 3-4 hours. what do you guys think.

i think your one of the luckier oso members who doesnt have to spend over a grand a day to be on the water!!!!!!!:lolhit:

22 gallons in 3-4 hours is nothin. That looks like a pretty stout SBC and probably making 350+ HP. At WOT it would probably burn 30 gallons per hour.

I agree. If you can get an enjoyable day on the water for less than a hundred bucks....your the one livin the good life sir. :drink:

primary jets seem way to large...but also might try a newer holley 650 or so DP...

please understand, i agree its not like my big boat older scarab with 509 s from a well known builder but just seems high on the consumption. this engine idles perfect never ever loads up, can idle around lake which has a shorline of 15 miles and sits right at 620 rpms in forward and never miss a beats. so its definately not over jetted on the idle side. Now i did run a marine edlebrok 600cfm out of the box and it was more then lean, had to close choke butterfly to keep it running. I was thinking of buying a new holley marine, but really not to shore on cfm, yeah do the normal cfm rating to match cubic innch but this a healthy small block, if anything, would rather over cfm it and jet it to what motor likes to run at.

Pulling kids around on a tube all day can eat through some gas - I know from my experience with my 25 Baja and 454. I can cruise around at 3000 RPM and not burn near as much gas as slogging around at 20 - 25 mph with the boat barely on plane. I'm sure yours is set up more for skiing, but it's still not a very efficient way to run. Factor in all the stops and starts you probably make for wipeouts, and I can see where you could burn through a tank of gas. Take it on an easy cruise for a known distance and check your mileage. You might be surprised.

I also agree that 92 on the primaries seems excessively rich. Have you tried running it leaner?

I agree that the jetting looks pretty rich, but stepping it down will have little effect on fuel usage. The carb is a on the large side for your cubic inches, so that is why you have to increase jetting.

The carbs jetting has absolutley nothing to with idle. The idle circuit is completely separate.

Nothing wrong with that fuel burn at all. I'm only making about 320 hp and WOT is 30 gal/hr. Cruise at 3500 is about 10 gph on plane all trimmed up

Well, I'll throw in here from my ski days. We used to run a Mastercraft comp ski boat all day long and around 20-25 gals, can't remember. 8 hours or so of slalom & wakeboarding, with 5 people on boaRD. Ski boats have fairly easy planing hulls (lots of flat area in back).

Now, this was before the days of water bladders to kick a big wake - if you are running one of those (or the fins that pull your hull into the water), your fuel use will skyrocket. If not, it sounds like you are running too rich. So, I'd try a smaller carb and get the jetting right.