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-   Archive through June 17, 2007 (http://www.wakeworld.com/forum/forumdisplay.php?f=464977)
-   -   Horse Power vs Gas -- engine size question (http://www.wakeworld.com/forum/showthread.php?t=462983)

jermiside 06-14-2007 11:38 AM

350hp Indmar engine is incredible reliable, and good on the gas. After ballast and sacing out my boat it takes a little while to plain out. I rode behind the X-Star with the 8.1 liter and it plained out quick--seemed like 30 yards or better--and this thing is loaded with weight. <BR> <BR>I thought that the 350hp would be economical--good power, save a little gas. Now factoring in the time/distance it takes to plain out I'm wondering if the 8.1 liter (how many hp is that?) would work to the same gas consumption? <BR> <BR>So the question is: Less power longer plain distance, or more power shorter plain distance--which is better on gas consumption? <BR> <BR>Anyone have any thoughts?

bennygoodx 06-14-2007 11:58 AM

Its 450 HP. I have that motor in my X-45. I love it. Very reliable so far...

jermiside 06-14-2007 1:22 PM

With ballast and sacs how would you rate the gas consumption? I'm thinking it may be splitting hairs. <BR> <BR>More power=less plain distance=less gas used to get upto speed. Less power=more gas longer distance to get up to speed.

hal2814 06-14-2007 1:23 PM

Even with the quicker time to plane, you're just not going to overcome the thirstiness of the 8.1L. It's like people claiming that their V6 automobile gets better highway mileage than the 4 cylinder equivalent because the V6 doesn't have to work as hard at highway speeds. It is true that the V6 doesn't have to work as hard but it's still sucking down more gas.

laraujo 06-14-2007 1:24 PM

It seems to me that the 350 would be more economical because you have 42% more engine (8.1 Liter) to inject fuel in than the 5.7 liter. Larger engines usually go into play as the size of the boat increase or you just want more Top End. For boarding all we care about is somewhere around 20-25 mph. Even if for argument sake the 8.1 got slightly better gas, what is the additional cost for it and does the cost saving from its fuel consumption cover the premium you pay for the additional size? My guess is ... NOT!

bftskir 06-14-2007 1:56 PM

jerm, <BR>i think you are referring to 350 cubic inches or 5.7 litres...generally 350's come in varying horsepowers like 285, 315, 340... <BR> <BR>i have a 377 Scorpion which is a 350 block "stroked"(longer connecting rods)to 377 cubic inches and mine is 377 horsepower and puts out 400lbs torque...it is the predecessor to the current 6.2 litre merc <BR> <BR>what a ballasted boat needs to get on plane is torque thats why the big block is better for popping 1000"s of lbs of ballasted boat out of the water it does not matter that you are only going to go 20-25 it takes the motor less "work" and gas to get the boat on plane

jermiside 06-14-2007 2:11 PM

So can I increase torq on my current motor? Re-prop maybe?

denverd1 06-14-2007 2:16 PM

what year star? newer ones come with the 14.5 x 14. Definitely reprop if your pitch is higher. a diff prop will make all the difference in the world. so check on that first. <BR> <BR> <BR>(Message edited by denverd1 on June 14, 2007)

laraujo 06-14-2007 2:28 PM

Jerm, <BR> <BR>What you will spend to pull the engine out of your boat, tear it down (to put longer conneting rods etc..) just to get the additional 22 ponies would not be worth the saving in gas. Get the sunk cost out of your existing engine spend time riding!

bftskir 06-14-2007 3:48 PM

leonard <BR>i don't think thats what jerm had in mind...and its alot more than just the connecting rods to get 377 horses... <BR> <BR>you can trade top end for more hole shot by propping for the weight if you are going around loaded with ballast all the time... <BR> <BR>that said... nothing really replaces horsepower or torque...

mikeski 06-14-2007 5:01 PM

I have a friend with a 8.1L X-Star and another friend with the 350MCX in an X-45. The X-45 uses less gas even though it is a bigger boat. I would say without a doubt that the 350MCX is the more economical powerplant under any situation. <BR> <BR>As a side note I find the growl of the 8.1 gets on my nerves after being on the boat a few hours. Sounds cool in the beginning but it gets old pretty quick. Tough to give the rider pointers while the motor is idling.

xaggie 06-14-2007 5:31 PM

This has been debated over and over again, usually without anything but seat of the pants opinions. <BR> <BR>Dante while you are correct in your analogy "cruising", it is the getting there that your missing. Your not going to have to run that V-6 as hard as the I-4 to get the same performance to speed ratio. <BR> <BR>As much as I'd like to love on my 8.1 and the fact that I can run 87 in it (89 to be safe). I'm NEVER going to make back my initial investment in less than premium gas savings. Nor when I sell my boat am I going to get all that much more money over an MCX boat (refer to gas vs. diesel towing vehicles). I'll say this, with 10 people + gear, 60gal of gas, all my stereo equipment, full stock ballast I'm damn glad I have the extra grunt. <BR> <BR>Also I'll grant you that you can do amazing things with prop pitch, size, and cup but your simply never going to get the same performance out of a 350hp 5.7 as you will out of a 450hp 8.1. <BR> <BR>What can I say? I'm likely never going to ride with 3000 pounds of extra weight, but I guess at least I know I can and then some. Better to have it and not need it than the other way around I suppose. Plus I'm already throwing that much money at the thing, might as well get all the bells and whistles. Matt

malibupilot 06-15-2007 7:25 AM

I think you can make up most of the difference with the right prop. Of course, you will have to give up a few MPH on the top end.

hal2814 06-15-2007 7:27 AM

I'm not missing the getting there, Matt. My point is that a bigger engine might not be working as hard but that doesn't mean it's using less gasoline. An 8.1L uses a heck of a lot of gas. There's no way in the course of general wakeboard driving it will be more gas efficient than a 350. If they were closer in size, you might have enough overlap to where the larger engine would be more economical (the 350 vs the 327 is a prime example in the automotive world). <BR> <BR>Now note that the original question is "which is better on gas consumption?" I'd probably still go with the 8.1L and just suck up the additional cost of gas if I were looking to buy a newer boat but you WILL be spending more at the pump.

paulw 06-15-2007 8:55 AM

My Xstar with the Mcx seems to do just fine. I am not loading it up with tons of weight, but it will pull your arms out if you gun in on start up. The new prop works great. I wish it got better gas consumption, I think if your really loading it down, the 8.1 ltr might be a little better on gas. I wish the boat companies would do an hr burn rate. I have seen this info on an offshore boats, it is nice to know, instead of all this speculation. They might not want us to know the Hourly burn rate though?

xaggie 06-15-2007 9:10 AM

I still disagree in the case of bigger displacment partial throttle vs smaller WOT. Then you get into questions of injector duty cycle and automotive closed vs open loop programming. I don't think that was the sprit of the original post. Thus I'll admit Dante that your right in your example about not being simmilar enough in size to justify saying the 8.1 could be more efficient. <BR> <BR>I will say this though, It seems to be the general misconception that you might as well stay near the marina because this eng. just sucks down the gas. In all the conjecture here the only people I've heard comment that the 8.1 is a gas guzzler don't even have one. After 3 years of LTR's, 1 1/2 with the LQ6, and the 8.1 for about 3 years, looking at the figures on my road tax refunds I've only used about 15% more gasoline. Again thats highly subjective to the amount and type of boating I did those years, but on the flip side I'll call you a liar if you tell me your using 50% less gas in a 350. <BR> <BR>Again it's all personal preference, but to answer the original question, although not working as hard your not going to burn less fuel getting the same performance in the 8.1 as compared to the 5.7.

rallyart 06-15-2007 9:34 AM

The original question was do you save gas by getting on plane quickly and the answer to that is yes. Coming out of the water and onto plane is an inefficient time for the hull and it has more drag so more power is needed. Like Matt implied it doesn't matter how you make it get on plane quicker. <BR>Is it a lot of fuel? No, but using lots of power to get past that quickly is more efficient that taking forever to get there. <BR> <BR>The rest of the time it has more to do with the operating efficiency of the engine at any given speed. Some engines are potentially more efficient than others because they mix the air and fuel better or get a smoother burn in the cylinder. <BR> <BR>To move the boat at any particular speed takes a particular horsepower. Any engine would be making the same power at that speed in that boat. A difference in the fuel use is just a difference in the efficiency of the motor. <BR> <BR>Of course, It's really fun to blast the extra power is you have it so you use more fuel. <BR> <BR>Real life use from anecdotal stories are what they actually get. Make a decision on engine based on your desires. If you use the power all the time you use more fuel. If you drive the boats the same you use just about the same.

bmartin 06-15-2007 11:51 AM

More from the seat of the pants....The time to get on plane of lets say 8 vs 12 seconds with the bigger motor can't possibly make up for the increased constant fuel intake while riding and idling UNLESS you are pulling someone who falls all the time. <BR> <BR>To put some objective info out there, I have a 22' Centurion with the 315HP 350MPI and run around 1800lbs of ballast and will use about 5 gals hour and use about 4 gals / hour with just stock ballast. <BR> <BR>Lets see some 8.1L fuel consumption numbers.

xaggie 06-15-2007 12:48 PM

Martin, I like the fact your trying to be objective about the matter, but dollars to donuts the consumption figures between an MCX X-Star and your boat would be noticeably different. If you were going to be completely objective you would need the same hull, same weight, and a set test pattern. <BR> <BR>That being said, I will do my best to get some hard figures this weekend. Matt

bmartin 06-16-2007 3:26 PM

I agree the hull will matter - if others post mileage of the same boats with different engines, we will get closer to some objective info but even then it will vary by the rider and driver and wind and water conditions, but at least it is something based on data.

xaggie 06-16-2007 7:20 PM

I agree, too bad it's nasty here this weekend <img src="http://www.wakeworld.com/MB/Discus/clipart/sad.gif" border=0>

ronskal 06-17-2007 7:23 AM

This is a thread for Travis Moye to answer. <BR> <BR>He runs a 5.7 MCX on his PWT X-Star and swears by it.


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