2000 Gulfstream w Twin ox-66 150's fuel burn??

[Down Time II]

I just bought this boat, my second Grady. I absoutley love the boat, can't say enough about it. I havent had a chance to put much time on it, its been off the trailer 3 times.
My concern is the fuel burn. As I said, she is a 2000 and has twin 2000 150 Yam ox-66. Wheels are pitched at 17, I believe. At about 4000 rpm im running 33-34 mph and the yam fuel management gauge bounces from about 19-24 gph, combined. WOT is about 5400 rpm and fuel management is showing around 40 gph.
This seems high. I know these engines are thirsty but I'm wondering if anybody has the same set up what kind of fuel burn I should expect realistically.

I have been reading about the ox sensor on tht and other sites. If this is fouled or not working properly would it cause these engines to burn that much more fuel? I was expecting 14-15 gph at cruise (3000 RPM). If my fuel management gauge is correct, I've got fuel blowing through one or both. But I have never noticed a fuel sheen to make me think either engine is running rich. Both engines seem to run perfectly. Had it over for a little while yesterday, 35-38 outside air temp, both started right up and ran smooth as silk.

The boat is full of fuel (140 gal). I have run it both with four buddies on a fishing trip and by myself, numbers appear the same.

Any advice?

 

[Finatic]

I have the same boat as you, a 2000 Gulfstream but I swapped out the OX66s last spring for a pair of f150s. Unfortunately you're fuel numbers are not that far off from what I saw when I had the 2 strokes. My typically offshore trip would average 1.3 mpg but I would often see as high as 1.6 on the ride home when the tanks were lighter. I think the performance data available was slightly inflated. I will say switching to the 4 strokes has been a huge difference, I have easily cut down my fuel cost by 30% for an average offshore trip. Hope this helps.

 

[Down Time II]

What kind of numbers are you getting with the F 150's?

Also, did you put 4 blade props on the 2 strokes? If so, what did it do to your cruise and top end at WOT?

 

[cgmiller]

Downtime..my dad has a 2001 ox66 150 on his 19 Mako. We have a fuel flow gauge on it that is pretty accurate. The speet wpot for his engine is 3400 rpms...his engine burns 7-7.5 gph at 3400 rpms. At 4000 rpms it jumps up to 9=10 gallons per hour. he has about 900 hours on his engine and it runs like a top..

I have a pair of F150's on my 23 Gulfstream and I average 2.3 miles per gallon. 3600 rpms is my seet spot, which sees 24-25 mph burning 4.5-5.5 gallons per hour per engine for a combined fuel burn of 9 to 11 gallons per hour. At 4000 rpms I am running 30 mph burning about 7 gallons per hour per engine....

 

[Finatic]

I never tried 4 blade props on my OX66s, just ran the 13.75 x 17 M props. In regards to the 150 four strokes, I seem to average just over 2 mpg on an offshore trip loads w/gear, ice, 180 gallons of fuel etc. The big difference in fuel savings occurs while trolling with the 4 strokes, they literally sip fuel.

Question for you Down Time, what kind of trailer do you have for your Gulfstream and what is the load capacity? I'm thinking of getting one for my boat but I want to make sure I get it right the 1st time.

 

[ahill]

My 272 with 225 OX 66's gets similar results as your #'s.
A friend of mine had a Gulfstream with twin Johnson 150's and would run from the Keys to Bimini, the Berry's and Andros regularly. Never asked about his fuel burn but the boat handled every sea he encountered.
Great boat.
He now has a 330.

 

[magicalbill]

Hey Finatic;
Thought I would jump in here; I have a 232 with twin 200's, circa 2007.
I ordered a custom trailer from Integrity Trailers, Nunica, Michigan. They overbuilt it frame-wise and put 5000 lb. axles on it with 16" wheels and load rang "C" tires, I believe.

It wasn't enough.....

The whole rig, loaded with fuel and ice weighed 10,100 lbs. at the Pilot truck stop Cat scale. Boat was 8K or so and the trailer alone weighed 1920 lbs. It felt unstable and swayed slightly over 65 mph. The bearings were wearing prematurely and once a weld broke going down the road.

Went to a knowledgable local guy and he replaced the axles with 7000 pounders, made sure they were lined up properly,(the originals wern't) and I've had no problems since.

Granted, I trailer a lot, but don't make this mistake. Get MORE trailer than you think you need, especially if your hauling any distance.

Even if you don't carry full fuel and your 150's will be lighter than my 200's, you have a heavy boat. My trailer is now a 14000 lb. cap. rig, and it tows like a dream.

To Downtime;

My burn numbers on my 200 four strokes are as follows;

1.8-2.0 MPG at 3700-3900 RPM; 27-30 mph.
It varies with sea conditions; if it's pancake flat, I can trim up a little more and get 2.1.

 

[Down Time II]

Thanks for all the help. I'm on a tandem trailer rated for 8000. Granted I don't go far on the trailer but it seems to be fine. If I was going any distance I would borrow my brothers three axle trailer. The 232 is wide and heavy but so far this is a freaking awesome boat.

My ox 66's are fairly low hours and run great. I'm planning on using them a couple of years the hanging a pair of f150's on the boat.