Question on GPH

[GaBoy]

I am running a maine GM 350/260 with a 2 bar carb. At 3000 rpms cruisng at 28 to 30 knots I am getting 14 gph. I am being told by some experts here that is too much per hour. My boat is 30' Searay Sundancer 1988. Just put new bottom end, all new including voted heads. Any comments to clear up a discussion. Does anyone have or know of the approx. avg on gph? Thanks.

 

[bruceb58]

Re: Question on GPH

For a 30' boat, that is excellent. You sure you are going that fast at 3000 RPM? Seems fast to me. Used to have a 28' Bayliner and with a 350, that thing barely got over 20 MPH at 3000 RPM.

Why only a 2 barrel carb?

 

[Fireman431]

Re: Question on GPH

Your 14 GPH is correct. I also wonder about that speed at 3000 RPM. Are you using a speedometer, GPS, or did you mean 4000 RPM?

There are a lot of people who maintain stats such as "...1 GPH per 10 HP per 2000 lbs of boat at sea level + 10%...blah, blah, blah", but I find there are way too many variables for a flat rate of fuel use.

Your use will depend on boat weight, hull design, power plant, HP to weight ratio, engine tuning, hull growth, etc. For a single 350 to move your boat to 26-30 kts/mph will require every bit of 14 GPH.

 

[cr2k]

Re: Question on GPH

Even if it was more GPH and your engine is running good and everything is right what could you do about it? Usually it is what it is.

 

[HT32BSX115]

Re: Question on GPH

I am running a maine GM 350/260 with a 2 bar carb. At 3000 rpms cruisng at 28 to 30 knots I am getting 14 gph. I am being told by some experts here that is too much per hour. My boat is 30' Searay Sundancer 1988. Just put new bottom end, all new including voted heads. Any comments to clear up a discussion. Does anyone have or know of the approx. avg on gph? Thanks.

Is that 14gph per side?

What are you using to determine GPH?

My 21" Four Winns (454 Bravo III) runs 30 MPH (GPS) at 3000 RPM and burns 10GPH (3mpg) measured with a Lowrance LMF-200 multi-function gage.

http://www.lowrance.com/upload/Lowrance/Documents/Manuals/LMF-200_0064-362_121306.pdf



You're doing 7gph per engine?





Regards,


Rick

 

[JoLin]

Re: Question on GPH

Okay, I went to the Searay archives- for 1988 they only have a couple models listed (not the OP's). The 1989 30' Sundancer came only with dual engines, so pretty sure we're talking about twin 5.7's here.

OP needs to provide more info- some of his figures are off. I doubt that boat will run 28-30 knots (that's what- 32-34 mph?) at 3000 rpms. 25-26 mph, yes. Only thing I can think of that might explain it is if he's overpropped. That'd hurt his fuel consumption, too.

At 3000 rpm, 14 gph per engine seems a bit high.

My .02

 

[HT32BSX115]

Re: Question on GPH

At 3000 rpm, 14 gph per engine seems a bit high.

My .02

Yeah. If it's propped correctly...........But I'll bet you could get 14gph per engine at WOT..............


14gph @30Kts would seem a little low for a boat that big too wouldn't it? (that is....if it would even go 30kts!)


I get about 24gph at WOT (4600RPM/57mph) with my carbed 454.

 

[45Auto]

Re: Question on GPH

The Sea Ray 300 design was identical from 1986 to 1989. 30 MPH or so at 3000 RPM is about right. They are supposed to get 1.1 MPG, which would give a total fuel flow of 28 GPH, or 14 GPH per engine (twin 5.7L). I haven't ran mine enough to verify that.

At $3/gallon for gas, that means it only cost about $90/hour to run the thing ....

Top speed is a little over 40 MPH.

My 1987 Sea Ray 300 heading to the place it likes best: