Fresh Air Exhaust Increasing Fuel Consumption?

We own a 2009 Mastercraft X-45 and recently we have been very concerned with an increase in fuel consumption. We have owned the boat since August of last year and ever since we got it back from our dealer at the beginning of this summer the rate of fuel consumption has almost tripled. In one example of the poor fuel economy we ran the boat for an hour with no ballast an only four passengers and we burned through 19 gallons. Our latest calculations show that we are going through fuel on an average day at about 17 GPH.

When we took the boat to our dealer this past week to have things checked out they said it was because the Fresh Air Exhaust was restricting the flow of the exhaust too much and this was causing the poor performance. In addition to that they said that if the apparatus was not removed immediately the warranty on the engine would be void. We have had the FAE on the boat since we first got it and we had one on our previous boat and we have never noticed this problem before nor have we ever heard of anyone else having the problem. Has anyone else experienced this? If the FAE isn't the cause of the problem what else should we be checking? Sorry for the long post, but any help will be very much appreciated.

Your dealer is smoking crack. I suppose you could take it off and then laugh in their face when your fuel consumption doesn't change.

Can you hook your engine to a computer to tell you what the problem is?

17 GPH! yikes!

Of course its probably decreasing fuel efficiency. Instead of free flowing out where it should, your exhaust is being angled, lengthened and is pointing straight down into the water. I understand the concept of FAE, but its purely retarded. Take it off and use some common sense - don't inhale exhaust fumes and allow your boat to perform as it should. FAE is for worry warts.

Also follow your scheduled maintenance schedule, replace plugs, wires, change oil, etc. as recommended. If its still burning that much fuel, you have other mechanical issues.

I'm with Tuneman.

Take it off, have the dealer fix your boat and then put it back on.

I say move this thread to the wakesurf board and see how many LMFAO replies it gets.Three seasons with one no added fuel consumption on mine.

This might be a stretch, but go with me.

I think the boat should use less fuel. Now I don't have to have the stereo up so loud. Which means the alt doesn't have to work so hard. Which means less hp loss. Which means better fuel economy.

FAE has no effect whatsoever on fuel consumption. If you check the FAE website there is information about how the FAE DOES NOT restrict airflow. Not sure what the dealer is thinking there. ALSO on the FAE website there is new testing done that shows the FAE creates a vacuum as the boat moves forward that actually INCREASES the airflow. I strongly disagree with Hyatt's post.

Also your stereo uses a very small amount of power (unless you're Grant with a super system) and your alt should produce more than enough power. Not to mention you probably have two batteries. Best of luck identifying the problem and if you are still worried about the FAE, give Larry at FAE a call, he will put that one to rest. And yes I am an FAE owner and absolutely love it.

Mikey, It was meant to be. But I support the info you posted.

Could be a sticky injector adding too much fuel. Could be clogged or jsut failed. Electronics will fail, sometimes a bad batch slips through and they fail early. I've found failed injectors before just by feeling each injector with the engine running. You can feel the pulses as they cycle and if one is bad you will feel it distinctly different from the others.

Does the exhaust smell particularly rich or do you ever notice any white smoke (unburned fuel) in the exhaust? FAE will likely create more backpressure (bad for performance/economy) but as stated it may create a vacuum effect while moving that could counter that. Either way any increase in fuel use should be minimal, not 3x the fuel.

Which engine is this and do you have the master muffler? It basically looks like a big FAE inside the engine compartment behind the engine.

FAE on my boat makes little difference in top speed. Top speed is using full RPM and max power. If the FAE is not affecting max power or RPM it is not affecting power output when exhaust demands are highest. Hence, it cannot be affecting exhaust flow significantly.

Have you changed the speed you are cruising at? If you've gone from cruising at 25 to cruising at 35 you will significantly affect your GPH.

Warranty can only be voided by something that directly affects the warrantied part. Changing a muffler on your car does not affect the valve train warranty, but adding a NOS system will. (I saw a jet ski with a NOS system on it. Great hole shot. Blew up the engine, twice.)

Just take it off for a weekend and see if fuel consumption changes. Easy test.

Did you add more weight to the boat for surfing? Did you change the prop? Anything else change? Those things can change fuel consumption.

Did you verify your figures via running the boat then filling it again or are you taking the gauges word for it? Also, could it be that you are much more closely watching it now than when you first got it last fall and the rate hasn't really changed? Just asking some common sense questions to help you narrow it down. Its sometimes easy to misinterpret results when you don't have a solid data set to base new findings on.

Cory - I will pay attention to the exhaust the next time we take the boat out but I haven't noticed that.

talltigeguy - We have the 400 hp engine. Not sure about the master muffler. Will check that.

Art - Our cruise speed is almost always below 30 MPH and it rarely even gets to that. Most of the time we are right around 25 MPH.

Tre - We have been using an additional 400lbs of ballast for surfing but other than that we are just running the factory ballast and we don't cruise with the ballast full. We haven't made any other changes to the boat.

Nic - Our numbers are based on filling up the tank at the start of the day, keeping track of the number of hours spent with the boat running and then filling up again immediately after getting off the lake. We were at Lake Powell a couple of weeks ago and it cost us over $50 to run the boat for a little less than an hour. We filled up, launched, drove out to a location that was about 25 minutes away (15 of which are spent wakeless) and then back. It was roughly 50 minutes of engine run time - never exceeding 30 mph, with 4 people on board, no gear or ballast. Correct me if I'm wrong but there is absolutely no way that should cost anywhere near $50 with gas prices just slightly under $3/gal. Admittedly, we weren't paying quite as close attention to this last year as we have been this year but we didn't have any alarming signs like this that something was wrong.

I appreciate the comments and hopefully I've answered some questions that might help a bit more. We have absolutely loved having the FAE so we are hoping that it isn't the problem. I think we should get to test without it this weekend.

I assume that you checked the number of hours by using the boat's meter, right?

Did you disconnect the boat from the trailer, or just the trailer from the hitch?

Just kidding

I could envision that there could be some exhaust restriction if you had the Master Muffler. Although it is pretty big, it could create 2 restrictions in series, and might conceivably be able to restrict the flow. But even with it, there is a lot of flow, so I doubt it.

Be sure to post back your results without it this weekend. I am very interested.

On my SV230 Enzo with the fresh air exhaust, 2500# of ballast for surfing plus three people and we use slightly less than 24 liters of gas per engine house. (3.8L per US gallon so about 6.3 gallons per hour). I would check everything to do with the ignition system. Plugs, cap, rotor, wires....

just my 2 cents

i will say my buddies x 45 with straight through exhaust did make me very light headed after a surfing session but we were back on the platform where you should not be and maybe the fae may help this some. but i do think it looks kind of weird and coming from a mechanic this in no way would make your fuel con. that much worse. if anything it would make it better and way more bottom end power. the only down fall i would say it may have is a little more wear and tear on the engine exhaust system increased exhaust gas temps.

and of course more dead fish. lol

Originally Posted by kawaik

When we took the boat to our dealer this past week to have things checked out they said it was because the Fresh Air Exhaust was restricting the flow of the exhaust too much and this was causing the poor performance. In addition to that they said that if the apparatus was not removed immediately the warranty on the engine would be void.

Classic response from any dealer facing warranty costs. It's BS, but there's no way around it. Really, you should have taken it off before taking it in - don't even give them the ammo.

I would be curious what Mastercraft and whoever built the motor would say.

Brandon mite be smokin crack too! LOL. FAE is the single most biggest improvement one can make to an inboard boat IMHO. And no it wont affect fuel consumption that much. Slightly, of coarse. You're dragging it through the water. You're bound to lose a MPH or 2 on top end as well.

If your driving habits aren't different and you are filling it consistently it has to be dropping raw fuel. That much should make the engine run poorly is it's a cold start injector stuck on or a badly leaking injector. Maybe you've got a leak somewhere. I would think you'd smell it if you had a couple of gallons of fuel in the bilge but who knows.
If it is a leaking injector or several, or if it is sensor that is putting in way too much fuel under load, your power will be down and you'll use more throttle to run the same speed which will compound the problem.
I suspect that Tuneman is right on his assessment and advice.

I would check a couple of other things. First have you changed/repaired or replaced the prop lately? A different pitch and/or a bent prop could cause different gas consumtion. Also how about your boat's transmission, do you see a different RPM at a certain speed you are used to ie: 20mph? Are you trimming the boat out differently than you used to with the trim tabs? Just a thought. I can tell you it isn't the FAE but I certainly would put the flappers back on when you visit the dealer. And I would get a second opinion from a different qualified Mastercraft dealer if possible. (emphasis on "qualified).

I have the same boat and engine with an FAE installed with no problems... something is up, but it's not the FAE

Fresh Air Exhaust and boat engine performance.
FAE is different from other exhaust systems; it is not passive but actively sucks the exhaust out of the engine:
The Fresh Air Exhaust video – FAE SUCKS
http://www.youtube.com/watch?v=T4AnNH0uTl8

The active suction of the FAE is why FAEs single exhaust outlet works so well without affecting engine performance.

The following speed tests were conducted on a 2001 Tige 20i and measured by GPS:

The loss of 1 mph top speed is due to the drag created by the FAE.

The following fuel consumption tests were conducted utilizing an electronic marine fuel consumption meter:

With FAE installed, fuel consumption is virtually unchanged.

With or without FAE fuel consumption jumps significantly at about 4000 rpm and exceeds 20 gph. Cruising at about 3500 rpm will use half the fuel compared to running at wide open throttle (WOT).

I cannot speak of warranty policies for the boat or engine manufacturers; that is up to them. Of the over 850 installations of FAE we have not heard once of an engine warranty being affected. A Mercruiser representative told one boat manufacturer that the FAE was similar to a stern-drive boat; a V8 engine with 2 exhaust pipes merging into one exhaust pipe and exiting underwater. FAE is essentially no different than the tens of thousands of stern-drive boat engine/exhaust systems. If a mechanic tells you that FAE causes excess backpressure, ask him if that is also an issue with stern-drive boats.

If a customer has any issues we ask them to send us pictures of the installation. We’ve had a couple of customers install the FAE backwards so it was scooping water in instead of sucking exhaust out. One of them ran a whole season like that. Even with the increased backpressure that would cause he said there were no performance issues. The only reason he even sent the photos was to get my opinion on a trim tab modification.

To Raging Jerbul, please contact us and please send pictures of your FAE installation. I will have you verify the depth of the FAE downpipe (relative to the propeller). If it is longer than necessary, there will be some excess drag but not likely enough to profoundly affect fuel consumption. We work with our customers to make sure their FAE performs as expected.

Here's what PCM sent me on my 2008 B52.
12 GPH isn't out of the question.


Gallons Per Hour

GPH
Idle 0.75
1000 1.3
1500 2.3
2000 3.8
2500 5
3000 6.09
3500 8.98
4000 10.15
4500 15.1
5000 19.1