Gas mileage on carbed supra

[wakeup]

I may not have posted this in the correct place but here's my question.how much fuel do you guys consume in lets say 4 hours of back to back boarding.
I have a 1988 supra with PCM 351,Borg Warner 1:1 tranny with acme 913 prop,1000 pounds ballet in rear and about 800 in front,Bennett trim tabs. I go thru a about 3/4 of a tank in 4 hours ( give or take a minute)that's with switching riders back to back.
My buddy has 08 launch and he burns less than a 1/4 tank n that time. I know there's alot of difference between fuel injection and him having perfect pass but that much difference. He also sacs out more than me and has usually three more people than I do.
Is it my carb or still having points or what. It's killing the wallet

[wotan2525]

In my experience, the newer fuel injected boats do not get very much better gas mileage than the old carb'd ones. The fuel gauges are incredibly inaccurate... I wouldn't trust that 1/4 drop indicated on the gauge had much relevance to how much by volume he burns. (Ie... if he has a 50 gallon tank, I really doubt that 1/4 on the gauge will come out to 12.5 gallons.)

On my friends mastercraft, the first 1/4 tank lasts forever and the last half of the tank goes FAST.

[haugy]

The extra 1800lbs, and the fact that you are going to have to run at a higher RPM, and the fact that Carbs if not dialed PRECISELY in can waste a fair bit of fuel......

Yeah, the other boat's going to out run ya in fuel. The fuel injected boats can burn less, not because they are that much more efficient engines, just the fuel delivery system is more accurate. A fuel injected can be the same or worse than a carb'd engine if not maintained properly.

This debate always goes on. But the newer boats were also designed with fuel economy in mind. Hull design, trim tabs, engines, fuel management systems, etc.

And I also agree with Wotan. Are you both running a 30 gallon tank? Because my buddies launch holds twice as much fuel as my Saltare. So yeah, his 1/4 of a tank is going to be more than my 1/4 of tank.

[docdrs]

In my opinion 99 outback 350 carb .....2009 21v 350mpfi cat is way better on gas, and its a bigger boat ,sacked out,and more peeps......I would say at 20- 25% better.......even I cant believe it :) ... just my experience and opinion

[TitanTn]

Are you both running a 30 gallon tank? Because my buddies launch holds twice as much fuel as my Saltare.

What size is your tank? My Saltare's tank is 50 gallons.

[cadunkle]

Haven't gotten around to measuring fuel on a purely riding day, but on a day of cruising around at 20-22 MPH mostly, with a small amount of idling through no wakes and a few WOT blasts I came out with ~6 GPH in my '89 Saltare with 454 and 800 CFM double pumper.

Interestingly enough this is the same fuel consumption my tow pig gets while towing the Saltare on the highway. Tow pig is a lifted '86 F-350 with 460 and 750 CFM double pumper. Makes sense though, with similar displacement and with those results I'd assume similar load on the engine.

As for carb vs fuel injection... I hate fuel injection. It's the tool of the devil and none of my vehicles are fuel injected. I won't trust it to something that I need to depend on to get to work every day, or depend on to keep me from being stranded in the middle of a shipping channel with tankers, barges, aircraft carriers, and whatnot headed at me. A carb is only as efficient as the person tuning it, and at the end of the day the same goes for fuel injection. Of course certain designs of each will be slightly more or less efficient, but more or less they're all in the same ballpark.

[cadunkle]

What size is your tank? My Saltare's tank is 50 gallons.

I figured 50 gallons from measuring external dimensions but owners manual says 46 gallon I think? Most I've ever put in it was just over 40 gallons, but of course it was still running when I put it back on the trailer...

[DAFF]

How does your boat seem to run?? Rich, smelly or hard starts can be indications the carb is out of wack and might be needing a rebuild. Driving style can also play a factor in fuel consumption. IMO 3/4 of a tank in 4 hrs seems on the high side. 5 gal an hour on fuel.....

[wakeup]

Boats not hard to start if u pump throttle a few times. It is very cold natured . U can't pit it in gear til it's warm or it will cut off. The thing I have noticed is if I let it idle for long periods of time it does seem to load up and will not clear itself out until I run the crap out of it.
Do any of you guys know the stock jet size in your holleys with 351w in them. Checked plugs and they're black in which I know is to rich.

[wakeup]

My tank is 37 gallon.emptied tank the other day with pump and had Ruffly 6 gallons left in it . So that's 31 gallons in 4 hours. Ive had this boat 4 years and nothing has changed except mileage. The boat still runs great. No leaks, same ballast, same lake, gas from same store, yearly tune up. But dam.... Something is causing it. I'm just venting on here guys . So bare with me. Wanna be on water more but it's breaking me.

[cadunkle]

7.75 GPH sounds kind of steep. If my Saltare with a 800 DP can get 6 GPH with no ballast I'd think in a lighter boat with a 351 you should be around what I burn.

Granted your 913 is a 13x10.5 which'll put you a fair amount higher RPM than me. I turn a 14x13. That might put you 800 RPM more at a given speed? I don't know for sure waht I turn at riding speed. What do you turn at 20-22 MPH? I wakeboard at 20.5 and kneeboard at 21, will check this Sat what my RPM is at that speed.

What RPM at riding speed? What carb do you have? What jetting and power valve? What's your initial timing and what does the curve look like? Is it advancing properly? Remove the air cleaner and see if you have fuel dripping from the boosters at idle or after shutting it off. Wouldn't hurt to do a compression check to see if your down a cylinder.

What was your old fuel consumption like? I know I've been out for 8-10 hours in the past without having to get gas, though I was pretty low and some of that was idling through no wakes.

[wakeup]

My boats at 3000 rpm at my riding speed which is about 24 mph. How do I check my timing advance.I'm going to check my jet size this weekend. Also wondering about drag or friction in drive train. Got under boat and tried to turn prop with motor off and in neutral and I can turn it but it isn't easy . Wondering if my strut bushing is worn or something. Transmission is brand new. I know its water lubricated. That was also with my shaft packing nut off because I'm replacing the packing and still hard to turn. Is that normal. . Also I run a 13 x 13 stainless prop when we go to another lake to just chill and gph still isn't what it used to be. Driving me nuts because the great running of the boat hasn't changed. Just gph

[cadunkle]

To check timing advance you need a timing light. You should be able to pick one up at any tool or auto parts store for under $50. Connect the power leads to your battery and the inductive pickup to your #1 spark plug wire. Find the timing pointer on the timing cover and the marks will be on the balancer. Wipe the marks off so they are clean and easily visible. With the engine idling point the timing light at the pointer and see what your timing is. Bring it to 1500 RPM and check again, 2000 RPM, 3000 RPM. You should have full timing advance by 3000 RPM, in the range of 32*-36* is typical. Initial should be 8*-10*. If you're not getting full timing advance the motor will be down on power and not run efficiently. If the curve looks goofy or doesn't advance, you will need to pull the points plate out of the distributor, ensure the springs aren't broken, and clean and lube the pivot points, advance plate, and anything that moves. After that you should have smooth timing advance. It's common for these parts to get rusty and not work smoothly in marine engines.

Also note, try not to keep it at 3000 RPM in neutral on dry land any longer than necessary to check the timing... Impeller and water flow and all that. It helps to have a helper to sit at the helm and bring it up in 500 RPM increments to 3000 to you can quickly read and jot down the timing at each RPM.

Jetting is always good to check to see if it's in the ballpark of what you'd expect for the motor. Different people over the years may have tweaked it a bit. It's not uncommon for someone who doesn't know any better to jet a carb rich to try to get more power, or to just swap another carb from another vehicle without tuning it. Also it wouldn't hurt to replace your power valve just in case it's ruptured. That would increase fuel consumption significantly as you'd always be running enrichment regardless of engine load or vacuum. If your engine has backfired through the intake the power valve may be suspect.

Before I replaced my strut bushings my shaft was hard to turn by hand. The old bushings were rubber style and were worn, but I get the feeling rubber bushings are just tight when not wet. After replacing them with those XPC fancy plastic type bushings the shaft takes a lot less force to get it turning by hand, despite the bushings being quite tight and a bit difficult to reinstall the shaft. I didn't notice any difference in fuel consumption but I wasn't measuring before and after.

[Lavinder]

I burn 3-4 gph in my ballasted 2007 22ssv on a day of surfing and wakeboarding. I document all my hours each day and fuel that goes in. The tank guage is fairly accurate (digital on dash).

[cadunkle]

I find 3-4 GPH hard to believe. Is the engine running that entire time? Is there any idling? When people talk about GPH I assume this is purely 20-23 MPH, negligible idling, minimal WOT or high speed runs, doesn't include any time the engine was not running, etc.