Help with GPH Burn!

[ArtWallach]

Help with GPH Burn!
Im very frustrated that my boat is getting such a terrible GPH burn. I have a B&G Engine Network Gauge that monitors fuel burn straight out of the engine's computer port. I bought the boat new in 2000 and used it for 6 years exclusivley. During that time I went on many trips and always burned between 22-24 GPH running at 3600RPM doing ~ 20kts. The boat was then leased out for 5 years and I just got her back the end of last year. Now after I've fixed the boat up to make her enjoyable to use again, the boat is burning 34-38GPH at 3800-4000 RPM running 17-18kts.
Over the winter I've had the props conditioned. The mechanics have been all over the engines. I know they say older boats get heavier, but I had a surveyor check the boat prior to getting it back and the hull has no wetness or moisture.
First question for you 310 Inboard Captains ... What RPM at what SOG providing what GPH Burn?
Second Question ... what can I check?

[dcharna]

The obvious question to me is: Are the fuel flow meters working properly? Did you check your meter against the actual burn. It seem improbable to burn that much fuel on your boat.

good luck

Dan

[islandhopper00]

Sounds like the props were changed to me. Whomever had the boat might have repropped because as the engines get tired they lose power. Hard to plane issues come up and the answer is to drop pitch.

OR

Whomever might have touched bottom and destoyed the props and a cheap set was found to replace them.

Just a thought.

[Henry Boyd]

I'm not sure its a flow meter issue. Our 496 burns 15-16 GPH at 3400-3500 and produces 20 knots. Bump that up to 4000 RPM and the GPH just about doubles and speed goes up to 29 knots. It sounds like the engines are consuming the proper amount of fuel for the RPM, but you are not getting the speed out of it. I'd have to agree on the suggestions for checking the props and bottom condition.

Henry

[rondds]

Forget the fuel burn for a moment. Art's running more RPM and getting less speed. That's a problem in and of itself. Assuming a clean bottom, I'd be confirming RPM with a handheld, then compression, then props. Once the problem is diagnosed, the fuel burn may come back to normal OR you then look at the accuracy of the B&G.

[ArtWallach]

Got the boat hauled and found out the boat has 16x15 props. It should have 16x17 according to the Sea Ray Manual. I guess the props got replaced when out of my possession withouot notifying me. I assume this would cause what I'm experiencing? Opinions?

[rondds]

Art
I'd speak to a reputable prop-shop. Atlantis in NJ is a PropScan shop and they know an awful lot about Searays. Give them a call and pick their brain. There's also one in Stamford, CT.

[Alex F]

Got the boat hauled and found out the boat has 16x15 props. It should have 16x17 according to the Sea Ray Manual. I guess the props got replaced when out of my possession withouot notifying me. I assume this would cause what I'm experiencing? Opinions?

Aside from Ron's recommendation I can add that you shouldn't take info from SR manual as-is. I've seen number of times where the props don't match SR specs, my boat is an example. So, there's very good chance that you have the same situation when during tests SR picked slightly different props to match your boat's hull and to achieve the best performance.

[its a circus]

Can anyone give me some names of companys that sell fuel flow meters besides Flow scan. I would like to conect these to a Raymarine MDF E SERIES.

[dpmulvey]

Alex F +1. What is your WOT RPM? That is where you need to start. The variables are infinite from there. The expertise here and a good Prop Scan shop will get you straight.