5.7 vs 8.1 in a 2006 @4ssv

I just sold my 1987 Supra Sunsport and loved it, now i'm needing some info before i buy my next supra.

i'm looking to buy a 2006 24ssv, my last Supra was direct drive and now i want more room for people and storage.

what i would like to know is what is the fuel consumption on the 5.7L and the 8.1L in that boat, and secondly would the 8.1 with a prop upgrade be pretty much the same consumption.

I mostly wakeboard and wakesurf and when i cruise around it's mostly 30-35mph, not a very big lake. we're usually 6-7 in the boat and when we wakesurf i usually put an 1100lb in the rear with front bags 100% full

it's not a question of not being able to afford the gas..... i'm just wondering if the 8.1 is overkill, or if i can tune it a bit to be a little less of a gas guzzler. i'm not familiar with the transmission gear ratios, but i'm guessing the 5.7 would run at higher RPM than the 8.1 at the same speed.

any help anyone can provide would be much appreciated,
thx

Smaller engine will have to run at higher RPM when weighted down. You'll have less top speed, so with the small block propped for surfing 30-35 may be pretty near wide open. Personally I'd never do a small block again, in a boat, a car, or a truck. Everything I own has a big block. Fuel consumption should be slightly higher with a big block, comparable or possibly slightly less than a small block when heavily weighted. Biggest thing is a big block will likely last more hrs before rebuild when weighted heavily.

thanks for the input, i've also heard that the big block tends to jam up if only running low speed heavily weighted, is there a serious difference between regular gas and super, i can understand super if i was trying to win a race, but i think the 8.1 has more than enough hp to go around,
any idea about type of fuel or do you recommend 1 tank of super for every 3 tanks regular?

my buddies 08 XStar has big block 8.1L . IT is STROOOOONG....but THIRSTY.
We were out on it a few weeks ago. after a few sets each, i was in driver seat and asked, DUDE, is your gas gauge correct??? YEP. it had burned that much gas.

No question, it has more than enough power, but it does drink fuel.

Don't know what you mean by "jam up", but if you run low speed heavily weighted, the more displacement the better. What we do on the water requires torque at low RPM. Small blocks are torqueless wonders and require gear reduction transmissions and small pitch props so they can spin to the moon to do teh same work a big block can happily do at 1000-2000 RPM less.

As for octane... An engine requires a certain octane rating fuel based on dynamic compression ratio, chamber design, and several other factors. Bottom line is if it needs 87 octane you are just wasting money putting anything higher in it. If it needs 89 or higher and you put 87 in it, even just once, you may hammer your rod bearings, crack rings, or even crack pistons. Use the required fuel for the engine. If you're unsure (old boat, non factory engine, blah blah) just put higher octane than you think it needs if in doubt. A new boat like you're talking about, just use the fuel the engine manufacturer calls for... Likely 89 octane but possibly 87.

cadunkle, i had heard that it was not so much the octane, but more the new ethanol blend fuel that was hard on seals and gaskets, i know it's an issue with 2 stroke engines but i'm not familiar how it is with an 8.1, i'll try and download the owners manual to see what grade they recommend.

hey brad is your buddy running with a stock prop, or upgrade, also when you say drinks gas, are you talking a $200, $300, $400 day of intensive riding?

thx

Munday
He has upgraded prop to max pull power. because of the lake we use on, it never gets run above tow/wake speeds.. sometimes up to maybe 30.. but we ride from and to the launch aas my buddy has a private launch.
20 gals for 2-3 hours riding is not uncommon. We used about 25 gals last trip for 3 hours of wake and surfing.. That was 2 sets each for 3 people of wakeboarding and 1 set each surfing..
SO $80-100 in fuel for 3 of us riding..
NO question, the motor is AWESOME. I have 340 ETX Cat in My 21V and full ballast and crew and you can feel a little coming out of the hole, 8.1 loaded, its a hammer and its like towing a trailer empty vs having the boat on it!!

The comments about Jam Up... his has been known to shut off at low RPM's.. but that was more when new than lately.

Having the 5.7 in the 22ssv, I would definitely get the 8.1 for the 24. Like everyone says, won't be enough motor if you get weighted down and full of people to capacity.

Brad thanks for the feedback, i used to run $100 days on average with my last supra, Carburated so when it on 4 barrels it got thirsty as well,

do you mind giving me the prop dimensions your buddy is running on his x-star,

thanks,

thanks Jzelt, i think after all i've read i'm reassured that i won't lack power or stop at every gas station, in the end what i save on gas with a 5.7 will only lead to accelerated wear and tear on the block.

cheers,

I had a supra rider with a 440 not I have a malibu 247 with the 8.1 and the motor is awesome and works great for the boat, I really dont find it too much of a pig on a day at the river probably 3-5 hours of riding I go through about $125 that was surfing and wake boarding with full ballast and 10-12 people and sometimes wedge.

I really don't find it that much worse than my old boat, and I have a 90 gal tank so when i do a weekend on the lake I never have to buy gas on the lake and pay and extra $1 plus a gallon

as far as props the boat came with a acme 537 13.5x16 the motor never had a problem spinning that prop but it did not pull out real fast loaded up now I have a acme 1273 14.5x14.25 150 cup and it pulls great and still runs about 45mph

Quote:

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Originally Posted by jzelt

Having the 5.7 in the 22ssv, I would definitely get the 8.1 for the 24. Like everyone says, won't be enough motor if you get weighted down and full of people to capacity.

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What prop are you running?

I have the 340 in the 24 and I don't feel like it is tough to get on plane. I regularly have over 2k in ballast and 8 people in the boat without any issues. Prop is the Acme 1433, which was an upgrade to the factory wakeboard prop that came on the boat.

When I was looking, I ruled out the 325. I was indifferent between the 340 and the 8.1.

Just for fuel consumption reference, I calculated over 3 tanks of fuel this summer an average of 3.7 gph. That's a 99 ish GT-40, 310hp, with my 21' Bravura, nice new acme prop, 1.23:1 transmission. Always with people in the boat (from 2 people to 12), sometimes ballast, sometimes pulling riders, some idling, some 35mph all over the lake. Anyway it's a reference point, 3.7gph.

Its a perfect reference point. I don't track mine though. Id put money on mine being higher than that, though, without a doubt.

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We have an '06 with the 8.1 and OJ 466 prop and have averaged 6.87 GPH from March 2011 to present day. We are closer to 6 GPH now cause we dropped 600 lbs to 2600 lbs and speed to 23.7 MPH at 75', RPM's are right around 3000. Overall it's a great boat. We've put 350+ hrs on ours since 2/10 with 1 minor issue. Hope this helps. Good luck with the purchase.

I have an 07 22 SSV with the 340cat.
I run the 1235 Acme which is similar to the Acme 1433 mentioned above but a bit larger diameter so i believe it should get better hole shot.

But with 2500 lbs in ballast with say 5 people it feels really doggish. It can get on plane but is sure working.

I've had occasion when weve had around 2000 lbs in the rear and everyone in the main cabin (6 people), no one up front and around 500lbs upfront and it took quite a while to get on plane.

I would suggest if you typically use alot of ballast to go with the larger engine. This is tough when looking used sometimes and cant get the deal when you want.

I would shy away from the 22 or 24 with the 325 however.

I had an earlier generation 22 hull (2005) - with the 325hp and the same acme 1235 prop and even with 2500lbs had no probs getting upto speed.