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Old 08-25-2006, 12:02 PM
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Default Fuel consumption diff: Yam 250 ox66 v 200 HPDI?

Last year a friend purchased a Yamaha 250 hp OX66 for his Aquasport 222. He had the choice of a 200HPDI or the 250 OX66. We have a difference of opinion with a friend over the fuel consumption difference between these engines. My friend thinks the difference would only be about 10% and I think it may be more like 30% less fuel consumed by the 200HPDI.

Would love some feedback to settle this.
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Old 08-25-2006, 12:11 PM
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Default Re: Fuel consumption diff: Yam 250 ox66 v 200 HPDI?

You are more correct. Don't know if it would be exactly 30% but the HPDI would be more efficient.
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Old 08-25-2006, 03:04 PM
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Default RE: Fuel consumption diff: Yam 250 ox66 v 200 HPDI?

I'm with A Few Dollars; I just replaced a carbed (not EFI) 150 with a 150 HPDI and my mpg has improved 28% so far. I'm guessing the OX 66 EFI would be slightly better than carbed, but not much.

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Old 08-25-2006, 03:23 PM
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Default Re: Fuel consumption diff: Yam 250 ox66 v 200 HPDI?

I just removed a set of 225 OX66s from my 25 Contender. Those engines are the same block and almost identical to the 250s. I repowered with 200HPDIs. Here are some examples: 4000 rpms used to be 26-29 gph, now it's 17-19 GPH. 3300rpms used to be 18-20 gph, now it's 12-14 gph. Those are fuel burn #s for twin engines, off the same Yam Fuel Managment gauge using the same exact props. Speed actually went up a mph(or two) at the same rpms. The lower unit on the HPDI 200 is much smaller and displaces less so it's more efficient. Much quieter engines, much smoother engines and a little lighter engines. I think the OX66s are 538lbs and the HPDIs are 475. I lost about 3 mph off WOT, I think. I really havn't tested WOT except once with a ton of scuba gear and three guys aboard I got 52 mph. I have seen 56 with the 225s and no load. I figure I can probably stretch 54 out of it with the 200s with no load, but who cares. My situation was a settup for a super improvment since the 225s were major overkill. If you buddies boat only needs 200hp to run correct then he should see major improvments also. The 250 will definatly shine if the load is enough to require a 250. Overloading a 200 will not see near the improvment I saw. I even could use the same props. If your buddies engine is only making 5200rpms or less right now you will need to go to a 19 prop with the 200 and then you might not be so happy as the 250 with a 21. It all depends on everything!
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Old 08-25-2006, 03:33 PM
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Default Re: Fuel consumption diff: Yam 250 ox66 v 200 HPDI?

there is actually a discussion on another website about this question. one guy with twin ox-66's says he burns about 175 gallons on an offshore trip out of charleston, sc which would be the equivalent of about 50-55 miles run offshore for a total day of around 12-14 hours. i have twin 200 yamaha hpdi's and do the same trip using 100 gallons.
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Old 08-25-2006, 04:57 PM
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Default Re: Fuel consumption diff: Yam 250 ox66 v 200 HPDI?

Depending on the boat and due to this being a single engine setup the 200 may have to work harder to keep the same speed and get it up on plane. The 250HP ox66 has bigger displacement (191Cu inch vs. 158.4 cu inches) and probably has a measureable amount of more torque. In this case the 250 will use a larger prop and run at less rpm to provide the same comparable speed, and provide time to plane in a shorter time span. So I would not say the 200HPDI will give 30% more fuel economy over the 250HP OX66 in this case. I would agree if you compared a 200HPDI to a 200 OX66.
You are not comparing on a consistancy basis. The 200 may provide some savings but I don't think it will be in the 30% range in this example.

The 250hp OX66 is 493lbs the 200hpdi is 466lbs. The weight difference is not that great.

OX66 for the same given HP vs. a carbed engine should save you about 15%.
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