I've had my "new" 99 Larson LXi 186 out for two weekends now and cannot
believe the gas consumption. At around 25 mph it uses about half a
tank per hour! I think it works out to around 2 mpg!!! I expected at
least 5 mpg, and even that would not be impressive.

I have changed the plugs since last weekend as they were a little
carboned up, but not bad. Can't see any improvement in fuel
consumption. I am planning on getting a mechanic to look at timing and
carburetor settings.

Anything else that folks can suggest I look into myself before that?
The boat has been lightly loaded and I think I am not messing up the
trim too badly, after getting some advice here.

TIA.

"Inno" wrote in message
ups.com...
I've had my "new" 99 Larson LXi 186 out for two weekends now and cannot
believe the gas consumption. At around 25 mph it uses about half a
tank per hour! I think it works out to around 2 mpg!!! I expected at
least 5 mpg, and even that would not be impressive.

I have changed the plugs since last weekend as they were a little
carboned up, but not bad. Can't see any improvement in fuel
consumption. I am planning on getting a mechanic to look at timing and
carburetor settings.

Anything else that folks can suggest I look into myself before that?
The boat has been lightly loaded and I think I am not messing up the
trim too badly, after getting some advice here.

TIA.


I would expect better fuel consumption. I get about 2 miles per gallon on a
21' 350 MPI engine aluminum jetboat. The plugs showing lots of carbon,
would tell me something is running rich. As to the 1/2 tank, just need a
bigger tank. I can run a little less than 3 days at Lake Oroville. Is
about 6 miles short of the ramp when I ran out of gas. 67 gallon tank.

Are you basing this on the fuel gauge? If so you need to measure based on
how much gas you put in it. Fuel gauges are notoriously inaccurate on
boats.

I agree with checking the timing. There are not any high speed or midrange
mixture adjustments on your carb. The main thing to check is to make sure
the choke plate(s) are coming fully open. If you have to dig further into
the carb the next thing to check is that the float valve is working
properly.


"Inno" wrote in message
ups.com...
I've had my "new" 99 Larson LXi 186 out for two weekends now and cannot
believe the gas consumption. At around 25 mph it uses about half a
tank per hour! I think it works out to around 2 mpg!!! I expected at
least 5 mpg, and even that would not be impressive.

I have changed the plugs since last weekend as they were a little
carboned up, but not bad. Can't see any improvement in fuel
consumption. I am planning on getting a mechanic to look at timing and
carburetor settings.

Anything else that folks can suggest I look into myself before that?
The boat has been lightly loaded and I think I am not messing up the
trim too badly, after getting some advice here.

TIA.

Yes I was basing it on the fuel gauge. Will need to keep track of fuel
in and distance travelled to get a better estimate. Good advice but
tricky when I am putting in $20 or $40 at a time.

I will check the carb plates as the carboned plugs seem to suggest a
rich mixture. Also, I did notice the fast idle was around 2500 rpm,
which seems a bit high.

Yesterday I let a friend drive the boat, since he has had boats like
this before (it is my first I/O). His opinion was that the boat was
not putting out 190 hp based on how long it took to plane. So whatever
is, perhaps, causing poor fuel economy may also be causing reduced
power. The boat did eventually get up to 50 mph according to the
speedo though.

James wrote:
Are you basing this on the fuel gauge? If so you need to measure based on
how much gas you put in it. Fuel gauges are notoriously inaccurate on
boats.

I agree with checking the timing. There are not any high speed or midrange
mixture adjustments on your carb. The main thing to check is to make sure
the choke plate(s) are coming fully open. If you have to dig further into
the carb the next thing to check is that the float valve is working
properly.


"Inno" wrote in message
ups.com...
I've had my "new" 99 Larson LXi 186 out for two weekends now and cannot
believe the gas consumption. At around 25 mph it uses about half a
tank per hour! I think it works out to around 2 mpg!!! I expected at
least 5 mpg, and even that would not be impressive.

I have changed the plugs since last weekend as they were a little
carboned up, but not bad. Can't see any improvement in fuel
consumption. I am planning on getting a mechanic to look at timing and
carburetor settings.

Anything else that folks can suggest I look into myself before that?
The boat has been lightly loaded and I think I am not messing up the
trim too badly, after getting some advice here.

TIA.

How big is the boat? Cuddy or bowrider? The v6 is a fairly decent engine.
Unless the boat is bigger that I'm suspecting it is or heavy I would expect
it to plan out fairly quickly with just a couple guys on it.


"Inno" wrote in message
ups.com...
Yes I was basing it on the fuel gauge. Will need to keep track of fuel
in and distance travelled to get a better estimate. Good advice but
tricky when I am putting in $20 or $40 at a time.

I will check the carb plates as the carboned plugs seem to suggest a
rich mixture. Also, I did notice the fast idle was around 2500 rpm,
which seems a bit high.

Yesterday I let a friend drive the boat, since he has had boats like
this before (it is my first I/O). His opinion was that the boat was
not putting out 190 hp based on how long it took to plane. So whatever
is, perhaps, causing poor fuel economy may also be causing reduced
power. The boat did eventually get up to 50 mph according to the
speedo though.

James wrote:
Are you basing this on the fuel gauge? If so you need to measure based
on
how much gas you put in it. Fuel gauges are notoriously inaccurate on
boats.

I agree with checking the timing. There are not any high speed or
midrange
mixture adjustments on your carb. The main thing to check is to make
sure
the choke plate(s) are coming fully open. If you have to dig further
into
the carb the next thing to check is that the float valve is working
properly.


"Inno" wrote in message
ups.com...
I've had my "new" 99 Larson LXi 186 out for two weekends now and cannot
believe the gas consumption. At around 25 mph it uses about half a
tank per hour! I think it works out to around 2 mpg!!! I expected at
least 5 mpg, and even that would not be impressive.

I have changed the plugs since last weekend as they were a little
carboned up, but not bad. Can't see any improvement in fuel
consumption. I am planning on getting a mechanic to look at timing and
carburetor settings.

Anything else that folks can suggest I look into myself before that?
The boat has been lightly loaded and I think I am not messing up the
trim too badly, after getting some advice here.

TIA.

It is 18 1/2 feet, bowrider, weighs about 2,300 pounds.

James wrote:
How big is the boat? Cuddy or bowrider? The v6 is a fairly decent engine.
Unless the boat is bigger that I'm suspecting it is or heavy I would expect
it to plan out fairly quickly with just a couple guys on it.


"Inno" wrote in message
ups.com...
Yes I was basing it on the fuel gauge. Will need to keep track of fuel
in and distance travelled to get a better estimate. Good advice but
tricky when I am putting in $20 or $40 at a time.

I will check the carb plates as the carboned plugs seem to suggest a
rich mixture. Also, I did notice the fast idle was around 2500 rpm,
which seems a bit high.

Yesterday I let a friend drive the boat, since he has had boats like
this before (it is my first I/O). His opinion was that the boat was
not putting out 190 hp based on how long it took to plane. So whatever
is, perhaps, causing poor fuel economy may also be causing reduced
power. The boat did eventually get up to 50 mph according to the
speedo though.

James wrote:
Are you basing this on the fuel gauge? If so you need to measure based
on
how much gas you put in it. Fuel gauges are notoriously inaccurate on
boats.

I agree with checking the timing. There are not any high speed or
midrange
mixture adjustments on your carb. The main thing to check is to make
sure
the choke plate(s) are coming fully open. If you have to dig further
into
the carb the next thing to check is that the float valve is working
properly.


"Inno" wrote in message
ups.com...
I've had my "new" 99 Larson LXi 186 out for two weekends now and cannot
believe the gas consumption. At around 25 mph it uses about half a
tank per hour! I think it works out to around 2 mpg!!! I expected at
least 5 mpg, and even that would not be impressive.

I have changed the plugs since last weekend as they were a little
carboned up, but not bad. Can't see any improvement in fuel
consumption. I am planning on getting a mechanic to look at timing and
carburetor settings.

Anything else that folks can suggest I look into myself before that?
The boat has been lightly loaded and I think I am not messing up the
trim too badly, after getting some advice here.

TIA.

"Inno" wrote in message
ups.com...
It is 18 1/2 feet, bowrider, weighs about 2,300 pounds.

James wrote:
How big is the boat? Cuddy or bowrider? The v6 is a fairly decent
engine.
Unless the boat is bigger that I'm suspecting it is or heavy I would
expect
it to plan out fairly quickly with just a couple guys on it.


"Inno" wrote in message
ups.com...
Yes I was basing it on the fuel gauge. Will need to keep track of fuel
in and distance travelled to get a better estimate. Good advice but
tricky when I am putting in $20 or $40 at a time.

I will check the carb plates as the carboned plugs seem to suggest a
rich mixture. Also, I did notice the fast idle was around 2500 rpm,
which seems a bit high.

Yesterday I let a friend drive the boat, since he has had boats like
this before (it is my first I/O). His opinion was that the boat was
not putting out 190 hp based on how long it took to plane. So whatever
is, perhaps, causing poor fuel economy may also be causing reduced
power. The boat did eventually get up to 50 mph according to the
speedo though.

James wrote:
Are you basing this on the fuel gauge? If so you need to measure
based
on
how much gas you put in it. Fuel gauges are notoriously inaccurate on
boats.

I agree with checking the timing. There are not any high speed or
midrange
mixture adjustments on your carb. The main thing to check is to make
sure
the choke plate(s) are coming fully open. If you have to dig further
into
the carb the next thing to check is that the float valve is working
properly.


"Inno" wrote in message
ups.com...
I've had my "new" 99 Larson LXi 186 out for two weekends now and
cannot
believe the gas consumption. At around 25 mph it uses about half a
tank per hour! I think it works out to around 2 mpg!!! I expected
at
least 5 mpg, and even that would not be impressive.

I have changed the plugs since last weekend as they were a little
carboned up, but not bad. Can't see any improvement in fuel
consumption. I am planning on getting a mechanic to look at timing
and
carburetor settings.

Anything else that folks can suggest I look into myself before that?
The boat has been lightly loaded and I think I am not messing up the
trim too badly, after getting some advice here.

TIA.




Idling at 2500 RPM is way too high. You need to adjust it down to 800.

That boat of yours should fly. I have a 20 foot cuddy with a Volvo 4.3 SX
engine and prior to bottom painting could get into the high 40 mph at WOT
with passengers aboard. It should also get up on plane fairly quick.

As others have told you.....you cannot use the gas gauge to determine gas
usage. Install an hour meter. Note hours run between fill-ups. Also
note gallons needed to fill it up. The method is not entirely accurate but
will give you a general burn rate when out for the day on the boat.

"Inno" wrote in message
ups.com...
I've had my "new" 99 Larson LXi 186 out for two weekends now and cannot
believe the gas consumption. At around 25 mph it uses about half a
tank per hour! I think it works out to around 2 mpg!!! I expected at
least 5 mpg, and even that would not be impressive.

I have changed the plugs since last weekend as they were a little
carboned up, but not bad. Can't see any improvement in fuel
consumption. I am planning on getting a mechanic to look at timing and
carburetor settings.

Anything else that folks can suggest I look into myself before that?
The boat has been lightly loaded and I think I am not messing up the
trim too badly, after getting some advice here.

TIA.


I have 4.3 merc 18.5 Chaparral, not sure of gph but for 1/2 tank approx 10
gal, I can tow kids on a tube for about 4 hours. The boat pulls me out of
the water one ski easily and I weigh 200 lbs. Top end about 50 mph.

If I had to guess I would say get your carburetor rebuilt, sounds like you
are dumping too much gas into the engine, especially if your plugs are
black. If you just bought the boat and are taking it to a mechanic, have
him do the whole tune up and carb rebuild, cap wires timing, change gear oil
etc. Unless you feel comfortable doing those things yourself....