Poor MPG on my 2006 Fiesta Vee 300

LivALil

Anyone know why I would be burning Almost 150 Gallons of gas on a 100 mile trip.  I'm running Volvo Penta 5.0 with F3 props.  Any help would be appreciated. 

 

Thanks,

Pete 

LivALil

I'm running at about 3400 RPM @ 28 mph

 

Lifes Good

there are a number of reasons why you might be only getting 0.66 mpg. but first we need to understand the conditions you were boating in. lake or saltwater... against current via river or tide? choppy or smooth? windy or calm? heavy load or light load of supplies? clean or dirty bottom?

based on your set up in calm non-current water you should have been around 1.25 to 1.50 mpg. if this was the case id start with new plugs wires and most important distributor and cap. also pull your props and check for rope of fishline wrapped on the shaft/hub. have the props ever been tuned by a prop shop? I tune mine every two years to ensure the best performance. after these things it gets a bit more complicated like compression check, computer fuel flow issues.

one other issue that is rare but can cause your engine to work to hard is over filled engine oil. however, low oil pressure generally is a symptom of frothing oil via the crank case.

LG

Lifes Good

oh... what drive do you have on the 5.0 vp? being that its a 2006 I hope its not the xdp plastic drive? if so start there! I had them and as one began to fail for its last time my fuel burn increase by 15% as the gears were failing and the gearlube oil sparked with metal shavings...

LaRea

Also check for bottom fouling.  Does the bottom feel rough to your hand, or nice and smooth?

Dream_Inn

Wow, that sounds worse than even my fuel burn.  I'd definitely start with the obvious that others mentioned.  Bottom growth is definitely one, but I'd think you'd notice a slow takeoff to plane.  Also if you had any of the fuel issues (which a lot of us with Gen III cooler's are dealing with), you'd also notice it harder to plane or more rpm's for same speed.

I think LG covered quite a few things to start with. Good luck and keep us updated.

raybo3

How did you know you burned 150 gallon's. Not to sound like a wise guy but are you sure your tank was full before you left for your trip? I never trust my feul gauge. Maybe you were not really full. Just a thought.

212rowboat

carb'd or FI?


if you're not noticing anything amiss with 'how' the engine runs:

- if carb'd, there is a chance you're choke is stuck.
- if EFI/MPI, there is a chance you're not going into closed loop operation...

Is this a twin engine or a single?

brianluck

I'd say check
The bottom as well

TonyWalker

LAL,

I think you just made the case for a fuel flow monitor system.  The simple ones are not too expensive.

Tony

Salt Shaker 342

Michael T

Hey LivAlil- how high above sea level are you? What was the air temp and humidity that day? Your 3400 rpm  producing 28 mph sounds about right. Load is a big factor with 5.0 liter engines - particularly if they're carbed. The carbed 5.0s have no where near the mileage that the EFI/MFIs get. Also 5.0s are way more susecptible to heavier boat loads than their bigger "small block" cousins - the 350s - again particularly if they are carbed. Details needed. MT

Black_Diamond

I've chased this problem too. I get ~0.8mpg. Been through all the noted checks, my 22P BIII is more likely the issue, but the 24P were bad on rpm and horrible performance. On 350MAG MPI: 3,800 rpm, 32gph, ~27mph

LivALil

I'm running Volvo Penta 5.0, fuel injected and just had the outdrives replaced last year with brand new ones.  I'm on the Delaware river in Philly so no barnacles.  I painted the bottom this year although there are some paint clips. 

 

I've judge my fuel consumption of the amount I put in so I've taking the gages out of the mix.   

 

 

brianluck

When were the conditions like, waves tide current wind?

LivALil

I have twins

LivALil

Conditions are traditionally a little choppy

 

LivALil

very little on board

212rowboat

if your engines aren't running rich- which I would be surprised to find they are both running rich (if it were just one, it would jump out at you), and the operating temperature of them is where it should be (160~175*), I'd sure go to something dragging...

it's not like you're that far out.. but.. are you running recreational gas or gas with ethanol?  That will make a difference, and maybe enough to knock you down to where you are.. also, a few dings on a prop could cause some weird slipping, and that 3400RPM could be getting you 30ish mph's... or, the other way around, 28mph could be done at 3200RPM, which could explain the slightly off economy you're seeing..

 

raybo3

You replaced your outdrives last year? Did you notice this problem before you replaced your outdrives? Is it possiable you have the wrong ratio???????? Again just thinking out loud.....

Black_Diamond

Ethanol blend will kill your mpg.

ohrgg1

I own a 276BR with a 496mag. When cruising at 30 or so mph, I typically get 2.5mpg. I recently noticed a significant drop in mpg, down to 1.2mpg. I checked for codes, had the bottom acid washed (there was a fair bit of growth) checked the fuel system and anything else I could think of. No dice. Then last weekend, a Big Bang nag the RPMs shot way up and the boat stopped dead. After getting towed back to dock, my mechanic confirmed my fear. The drive was shot. It was a mess inside. His theory is that something in the lower locked up which then broke the input shaft and ate everything else in the process. Thankfully, it's covered under an extended warranty or I'd be on the hook for a $6500 repair. Looks like the poor mpg was a problem in the drive all along. Sorry for rambling, but its something you may want to check.