Fuel mileage Question?

[hbpaints]

I realize this is a very "open ended" question based on many factors, weights, weather, conditions, etc... But What I am looking for is a GENERAL idea of what to expect from my boat in the way of Fuel consumption? I am a newbie... so have lots to learn...

I have an older (late 70's, early 80's) 26' Flybridge cruiser with a semi planning hull. 350 Inboard & a Volvo 280 Duo Prop leg.
It's a TollyCraft "Clone", (read as heavier boat... lol)

It currently has 2, 40 gallon aluminum tanks installed in it and I am trying to calculate or determine an "approximate" fuel consumption for this boat?
At full throttle?
Cruising ?
etc...

As mentioned, I realize this is a very vague question, but there must be some of you out there with similar setups that can give me an idea of what to expect?

Reason I'm asking is to try and see if I can add yet another fuel tank onto the boat for more range... Or can I get to where I want to go without packing a lot of jerry cans... lol
My goal is to be able to travel at least 2.5 hours out... Fish with my kicker (on a separate tank) and then drive 2.5 hours back...

Thanks in advance for any input... I apologize if this has been asked before... I couldn't find anything in the forum search.


Rob.

 

[Scott Danforth]

0.4# of fuel per HP used per hour

However so many variables such as wind, currents, etc affect your fuel economy, the best way is a totalizing fuel gauge

 

[Bob_VT]

Rule of thirds Use a third going out and a third coming back and the last third is your reserve

 

[MH Hawker]

the only real way to know is to fill the tanks run it a hour and refill

 

[mr 88]

My guess would be 1,4 to 1.7 MPG @ cruise / 3000rpm. WOT and your at less than 1mpg. You want to go 50 +miles offshore [ cruising @ 22 mph ] on one engine and a kicker that would be pretty much useless if a storm came up out of no where. At 1.4 mpg and cruising your running on fumes coming back No thanks

 

[roffey]

if its has two tanks I assume you have to switch them over once one runs out. I would think 80 gallons of fuel would last 5 hours. Take the boat out for the day and see how long 3/4 of a tank will last. I have a small runabout so I really do not know what I'm talking about here but, I would be more concerned about only having one motor and going 2.5 hours out to sea?

 

[hbpaints]

Sorry, I should have made that clearer... I'm not heading 2.5 hours out to sea... I'm 2.5 hours trip from the marina down the Douglas channel (no open water) to another fuel dock... What I was trying to determine is if I can leave the marina, travel 2.5 hours on the one tank, use the kicker to fish, and then have enough in the other tank to get to the fuel dock/remote marina that is about another 20 minutes away.

From some of the above comments, I should have more than 2.5 hours runtime on 80 gallons of fuel ?

I was told by a couple people that I should expect 20 gallons per hour in this boat... I assume that's WOT...

MK Marina in Kitimat to Hartley Bay... It's in the Douglas Channel (North coast of BC...) no open water...

Again... I apologize... Newbie to boating.... and yes, I will be putting on the lake first this year to learn the boat before going out on the ocean...

 

[SkaterRace]

You should be fine that 20 gallons an hour does not sound far off from what I would expect at WOT

 

[Sea Rider]

Need to check max wot rpm range as will be currently loaded, dial a prop that will rev I/B at near full wot rpm range. OTOH, nobody really runs wot, full hammer down all the time, good for fast plane, once there, throttle less to maintain a perfect plane with less fuel consumption. Fuel consumption will depend based on load & how fast you want to be there...

Happy Boating

 

[Old Ironmaker]

As you said they are many, many variables. When I wanted to determine my fuel range when I bought my boat I ran with a full tank on plane for 20 minutes out and did the same back to the marina in the conditions I would normally boat in. Then I filled the tank and determined my gallons per hour. I love Kitimac by the way, you are in God's country for sure. There are fish in them there waters.

 

[frantically relaxing]

I have an older (late 70's, early 80's) 26' Flybridge cruiser

Fiberform made tons of those, and they just won't die-- Just curious if that's what you have?

Gas mileage-- a 26' cruiser with a 350 is going to need a tight prop just to get on plane, like a 17"er -- this means you'll be running 3500-3600 to maintain a 30 mph cruise. At that rate you'll be getting between 1.0 and 1.5 mpg. My bet is about 1.2. At displacement speed you might muster a little over 2 mpg. WOT will put you down to 0.5 to 0.8 mpg.

FWIW, my Party Cruiser, from mine and the OO's notes from day one was getting 1.2 mpg at 12 mph with the 115 hp outboard. HOWEVER- I've since discovered that the oil injector was supplying almost 100% too much oil, (gallon of oil @ 27 gallons of gas) and the jets in the carbs were oversized even for sea-level. I mention this because even from the dealer this boat was setup totally wrong for 4000' altitude, and should get much better mileage-- which means with some astute tuning (think dead-on timing, and maybe a new Carter marine carburetor which is very adjustable without spilling a drop of gasoline), and possibly a fuel flow gauge to monitor your gas useage to optimize your speeds, you might be able to get closer to 2 mpg...