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Yamaha ox-66 Running great but killing the gas!!! Yamaha people help with advice

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Yamaha ox-66 Running great but killing the gas!!! Yamaha people help with advice

Old 06-17-2013, 12:15 PM
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Default Yamaha ox-66 Running great but killing the gas!!! Yamaha people help with advice

23 GW Gulfstream w twin 150 0x 66's. Made a canyon run Saturday (approx. 70 miles) and ran out of gas 30 miles from the dock. Fuel capacity is 140 and I had 30 gal of fuel brought out to me. I know that 70 miles is pushing the range limit especially after trolling all day, but I should not have run out of gas. Total gas for this trip was 170 gal. I know this boat is not the poster child for conservation, but I'm burning way too much gas. The thing is, the motors are running great. The one problem I have is that the stb motor, at cruise, burns 2.5-3.5 gal per hour than the port motor according to the FM guage, which I am putting more faith in. I figured this was a faulty sending unit, especially since the total fuel burn on the FM gauge was indicating I had burned 57 gallons out of a 48 gallon tank.

So I talked to the Yamaha dealer mechanics (friends of mine) they suggest starting with checking for bad diaphrams in the lift pumps. I've got my fingers crossed, but I cant help but wonder if the diaphrams are leaking wouldnt the motor run rough? This thing should be leaving an oil slick its burning so much gas.

Anyway I was hoping to get some advice and ideas on where else to look. If this is the way its going to be, there's going to be a Gulfstream for sale real soon.

Thanks in advance for any advice I can get.
Old 06-17-2013, 12:57 PM
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Help me out here... you ran 70 miles there and 70 miles back and trolled all day - having a 140 gallon tank?

So for shits and giggles lets say 170 gals (includes the 30 dropped off). I am making an assumption here - but let's say you trolled for 4 hours... 7mph and we will round to 30 miles trolling. That's 170 miles on 170 gallons.

Not being familiar with your boat - but being somewhat familiar with OX66's - 1mpg is probably about right cinsidering a full load of fuel, ice, coolers, people, gear, etc...

My Scarab 302 with 2 OX66 250's CAN get 1.76mpg under the right circumstances - but if there is chop, waves, anything that requires me to run at less than optimal cruise speed - yeah... it fallls off. My last trip was 125 nautical miles round trip - burned 113 gallons - basically 1.1mpg with 4 guys, ice, beer, gas, more gear...

Sorry - but I that's not too far off. Just becasuse your (a) boat CAN do it doesn't mean that it always will.
Old 06-17-2013, 12:59 PM
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And do a better job of planning - your margin of error rate sucks.
Old 06-17-2013, 04:20 PM
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Less than 1 mpg does not sound right to me for twin 150's.. Are you sure that you had 140 gallons?

I would think 1.76 mpg unless your running WOT all the time...
Old 06-17-2013, 04:53 PM
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Originally Posted by Blue Chip View Post
And do a better job of planning - your margin of error rate sucks.
47 echo romeo requesting immediate come around.
Old 06-17-2013, 04:59 PM
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Blue chip thanks for your advice. The farthest away from the dock I was was 70 miles. At that point we began trolling west so your calculation of 170 is off a touch. But what ever. You say you have a pair of 250's and burn 1.76 gpm. That would be acceptable to me. That is kind of what I expected when I bought this boat. If I pull out my handy calculator, even at 1.5 gpm I should have had a 210 mile range. The fact that I missed it by 30 miles is a pretty good indication something is not just right. Btw, over 25 years of boat ownership, using my boats practically every weekend, I've been towed in 2 times. Granted this was the most embarrassing, but I think I've got a pretty damn good "margin of error". Can't count the number of times I've done the towing.

Engedge I am positive I had two full tanks.

I guess I was hoping for some actual useful advise not judgment and criticism on my margin of error....anybody have anything useful to contribute?
Old 06-17-2013, 05:07 PM
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if its running great......

are your pickups sucking off the bottom of the tank ??
Old 06-17-2013, 05:07 PM
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They probably burn around 9 GPH @ 4000 RPM each. Something is definitely off. Clogged O2 could be causing a rich condition?
Old 06-17-2013, 05:22 PM
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What is your max RPM? Sound like an O2 or LP issue. Change out the LP's and see if it improves. I get at least 1 MPG with my 35 Contender so something is not right. When my LP went I started burning about 5gph more and would not hit top RPM, but would crank and idle fine. I would not have known the issue if I did not already know about my avg GPH for both motors.
Old 06-17-2013, 05:32 PM
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Originally Posted by wetneck View Post
if its running great......

are your pickups sucking off the bottom of the tank ??
X2 on the fuel pick-ups. Maybe you still had fuel in the tank but the pick-ups are bad and not reaching the fuel in the bottom of the tank. 1MPG seems like a lot of fuel to be burning.

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Old 06-17-2013, 05:37 PM
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he says its running good.......its NOT gonna run good with bad lp pumps, more than likely burn up after a 150 mi run
bad 02 can burn it up also
pickups should NOT hit the bottom
Old 06-17-2013, 05:40 PM
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Subscribed. I'm working thru the same issue with my 225 ox66 on a 20' Privateer. At best I see 2.0 mpg. My last offshore trip I struggled to hit 1.0 mpg on the way out (granted it was into the wind and seas). I just replaced the LP pumps prior to the trip. I'm looking at the O2 sensor and TPS sensor now. How is your oil consumption? My oil consumption is also very high, I'm going to be revisiting the oil pump adjustment also.
Old 06-17-2013, 06:04 PM
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Originally Posted by Down Time II View Post
Blue chip thanks for your advice. The farthest away from the dock I was was 70 miles. At that point we began trolling west so your calculation of 170 is off a touch. But what ever. You say you have a pair of 250's and burn 1.76 gpm. That would be acceptable to me. That is kind of what I expected when I bought this boat. If I pull out my handy calculator, even at 1.5 gpm I should have had a 210 mile range. The fact that I missed it by 30 miles is a pretty good indication something is not just right. Btw, over 25 years of boat ownership, using my boats practically every weekend, I've been towed in 2 times. Granted this was the most embarrassing, but I think I've got a pretty damn good "margin of error". Can't count the number of times I've done the towing.

Engedge I am positive I had two full tanks.

I guess I was hoping for some actual useful advise not judgment and criticism on my margin of error....anybody have anything useful to contribute?
As humans, we do not like being told we may have made some bad choices.
That would be me. 57 stiches on Mothers day when I was 12. Someone was playing golf. He saved my life. I still puke fuel on the troll. Not sure I could make West End with 47 useable in my pig. Not many straight lines in the ocean. 20 ft single. Twins eat twice as much.

Cheers,
Us
Old 06-17-2013, 06:16 PM
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Since this thing is so thirsty I rarely run over 3800 rpm which is where I ran it Saturday. Weather was beautiful, seas rolling 1-2. Just for the record I bought this in Jan and this was my first off shore trip. I generally err on the side of caution. But both motors true up to around 5500 RPM and the boat runs about 48 mph WOT. I cleaned o2 sensors on both about a month ago. Just checked all four lp pumps for leaking or bad diaphragms but they seem to be good.

This has got me flustered. I don't get how these motors can run so good but be burning so much gas. Last time I ran WOT the FM gauge was showing 44 GPH. I always understood the 2 strokes would burn 10 % of the hp at WOT, ie, a 150 should be 15 GPH at WOT. I was expecting 14-16 GPH at cruise but at 3800 the FM gauge is consistently showing 18-20 at cruise.

Any ideas on why the stbd motor would burn 2.5 to 3 GPH more than port at cruise?
Old 06-17-2013, 06:20 PM
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BTW oil consumption seems fine.
Old 06-17-2013, 06:29 PM
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Actually consumption tends to be around 22 GPH cruising 28 mph w the wife two young kids and a dog with 40 gal of fuel. Hate to belabor the point but this is worrying the crap out of me. I used to make the same trip w a 22 seafarer w a single F225 on 70 gals. I know the 2s and the 4s are different but I can't believe it would take another 100 gals.

Thanks for the input.
Old 06-17-2013, 06:30 PM
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Originally Posted by Down Time II View Post

This has got me flustered. I don't get how these motors can run so good but be burning so much gas. Last time I ran WOT the FM gauge was showing 44 GPH. I always understood the 2 strokes would burn 10 % of the hp at WOT, ie, a 150 should be 15 GPH at WOT. I was expecting 14-16 GPH at cruise but at 3800 the FM gauge is consistently showing 18-20 at cruise.

Any ideas on why the stbd motor would burn 2.5 to 3 GPH more than port at cruise?

I've always been under the assumption that WOT at 5,550 they should burn 20gph per side. At least that's what mine burn and my mechanic told me thats spot on
Old 06-17-2013, 06:35 PM
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Skatsurfr would you give me more idea what you burn at cruise and rpms you turn, etc?
Old 06-17-2013, 06:51 PM
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Default OX yams are not the most fuel efficient. They almost never blow up.

Originally Posted by Down Time II View Post
Since this thing is so thirsty I rarely run over 3800 rpm which is where I ran it Saturday. Weather was beautiful, seas rolling 1-2. Just for the record I bought this in Jan and this was my first off shore trip. I generally err on the side of caution. But both motors true up to around 5500 RPM and the boat runs about 48 mph WOT. I cleaned o2 sensors on both about a month ago. Just checked all four lp pumps for leaking or bad diaphragms but they seem to be good.

This has got me flustered. I don't get how these motors can run so good but be burning so much gas. Last time I ran WOT the FM gauge was showing 44 GPH. I always understood the 2 strokes would burn 10 % of the hp at WOT, ie, a 150 should be 15 GPH at WOT. I was expecting 14-16 GPH at cruise but at 3800 the FM gauge is consistently showing 18-20 at cruise.

Any ideas on why the stbd motor would burn 2.5 to 3 GPH more than port at cruise?
Usually they get too rich on fuel and run like crap when the O2 and other things are out of whack.
HPDIs are more fuel efficient. They burn lean. then when they burn too lean and have a hick up, they Blow up. Boom!
Old 06-17-2013, 06:58 PM
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You might want to get a flowscan. My OX66 200 has best fuel economy at 3600 rpm 8gph

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