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Am running a 1997 Proline 251 Walkaround with a single Mercury 225 OB. Running offshore am getting about 1 mile to the gallon running 22 to 28 MPH depending on seas. Is this the best I should expect? Should I slow down? I trim the bow down some to get a smoother ride. Is this the correct approach or trim the bow up and let it pound off the waves? Thanks. If I repowered with a four stroke what would be the best choice for this boat? It is rated to 300 HP. Thanks
dumb question...... what is the max rpm that engine reaches,when the boat is ran with a normal load.by normal load,what i mean is in the conditions in which you run off shore ??
__________________ don't try this at home....i'm a profesional......
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jim anderson jimmy's marine service llc
a 5 star wrenchin' whore !!!
I was running a proline 241WA with the Merc 225EFI and was averaging 1.7mpg. Repowered with a Merc 225 four stroke and now average 3.0mpg running at the same speeds. Usually cruise now at about 4200 rps; 27mph burning 8 GPH with the motors trimmed up pretty good. The real advantage of the 4 strokes is at trolling speed 3-5mph burn less than 1 gph. I have a flow scan meter so can watch my fuel burn closely. I know your boat is the next size larger, but your improvement should be similar. I would recommend you move up to the 250 Yamaha as your boat could use the extra power. Repowering with the Mercury Verado is a complicated and much more expensive process because you would need all new controls and guages.
1 mpg is pretty bad, even for a 25' boat. Something is wrong with the engine or calculation. I would guess you should be getting 2 mpg or a little under at 4000-4500 rpm. I've found tabs and trim aren't that variable offshore as you often have to trim down. When I can trim the bow up in calmer conditions I always get less fuel burn. Re-powering to a 4 stroke (250 is a good suggestion) or DI 2 stroke would probably improve your mpg number by 40-50%.
I am not familiar with that boat but it seems that most 25 WA boats would be severely underpowered with a single 225. Being underpowered will kill efficiency as quickly as anything.
What rpms are you running at to achieve 22-25mph? Something doesnt sound quite right. According to Pro-line specs our boat should run upper 30's with a single 225 (http://daveymarine.com/251_wa.htm). I know the numbers are off or from a very light load being I had a 1997 231 w/ single 225 offshore merc. so I know those engines drink fuel and oil. However, at 25gph your engine is probably at over 5000rpms. I would think that at 22-25mph your engine wouldnt be wound up that much.
I will say that I now have a 25'er with a single 225 Optimax and burn around 10gph at 4000rpms according to my smart craft. If you are looking to upgrade and get MUCH better economy, dont over look the opti. It will be a lot less expensive to repower since you already have merc controlls.
I will have to check RPM at various speeds. I want to say I am over 5000 at around 28 MPH, but that is truly a guess. Maybe I have a prop issue? The prop blades do look slightly flattened in their circumference at the outer edge. Is this a common wear pattern with SS props? Thank you all for your expertise. With gas prices as they are, I sure would like to improve the situation! It will be 2 weeks before I can check RPM's
Go to the Mercury site and check to make certain you prop. is the right one for the weight and length of the boat. Sound to me that you might have the wrong one on the engine. I had a 21 foot Proline that had the wrong prop. that had a 150 Merc. on it and I was getting 1 mpg. I changed the prop. and I came up to 5 mpg.
I ran a boat like yours a few years ago it had an efi merc 225hp it also got the same fuel burn of 1 mpg. The motor was changed to the opti max 225 a few years later the mpg more than doubled.
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DF250 Suzuki & Owens & Sons Trailer
Before you go looking for the engine, is your bottom painted? Do you have a clean hull? I have know those that have so much bottom fouling that they could hardly plane. This is just a suggestion.
also do a compression check if it's lazy when you hit it you may have loe compression My 231 with a 225 offshore was a pig on fuel your speeds seem down for that power5200 should be around 38-39mph with a fuel burn close to 30 gph with a 17p mirage
To get maximum efficiency out of a prop the edges can't be banged up. You can practically shave with a good racing prop. Of course pitch and diameter are critical. You may want to check to make sure that your engine is installed at the proper height.
The hull is not painted and is clean. I keep on a trailer. I will check out RPM's. If I take the prop to a prop shop, and tell them what boat I have, can they tell me if it is the correct prop for a given boat or is this more trial and error? Or will I be able to tell more once I know my RPM's at various speeds?
I just did a trip which was mostly high speed cruising. I have a 23' Polar with twin 140 Suzi's 4 strokes. I burned 60 gallons in 10 hours. I didn't keep track of the miles so I can only give you a gallon per hour rate. 6 gph is pretty good I think.
He's probably close to WOT, since he's significnatly underpowered with the 225 single. 28 GPH is not unreasonable for that motor, which is wound up at 5500.
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A bad day fishing is always better than a good day at work.
That is way to much. I have a 25' trophy walk around w/ hard top and with the 220 hp I/O
Fully loaded with 3 buckets of chum, 106 gallons of gas, 4 people, gear & ice I burn 13 gallons per hour heading out cruising about 22mph and about 10 gallon per hour heading back cruising about 24mph (once I burn the fuel off and get the chum buckets out). I purchased a flow scan for it and that was one of the best things I could of done. I didnt realize it, but by cutting back on the throttle and having the trim tab all of the way down, I got the best performance when fully loaded.
Tim
Fuel Economy 
