Fuel range on a 1988 sundowner 215
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Author:  cjp555 [ Thu Jun 17, 2021 10:25 am ]
Post subject:  Fuel range on a 1988 sundowner 215

Hi I have my "free" Sundowner running. Looking to see what the approximate gph or fuel range is for the 205hp?

Update on boat below.

UPDATE For all that offered, thanks. The distributor was 180° off and the carburetor was not tightened.... after I did a quadrajet rebuild and timing it ran well. Awaiting a vacuum Guage to set carb and then on to the next set of problems.

Author:  Surface Interval [ Thu Jun 17, 2021 7:59 pm ]
Post subject:  Re: Fuel range on a 1988 sundowner 215

There are a lot of variables for fuel economy. Speed, how much weight is being carried, outdrive trim, clean hull bottom, etc. According to Four Winns Fast Facts, the boat should have a 50 gallon fuel tank. Our Four Winns 190 horizon (dry weight about 2500lbs) got a little over 4 mpg at about 28 mph and 3000 rpm. This is based on fuel added at the pump and approximate distance traveled. Our 268 Vista (dry weight almost 7000 lbs) can get up to about 2.3 mpg at about 27 mph and 3700 rpm when light. This is based on afuel flow transmiter and real time figures. The worst cruise speed for fuel economy is at fast displacement speeds. With no wind or current our 268 will show between 4 and 6 mpg at 600 to 1000 rpm. At 1500 to 2500 rpm and fast displacement speeds around 10 mph, the fuel economy can be around 1 mpg.

I would estimate you boat would be able to get approximately 3-3.5 mpg at ideal economy cruise. As a suggestion, I recommend running on the top half of the tank, rather than running out. You never know what else you might decide to do while on the water. Also, be aware that fuel gauges are notoriously inaccurate below about 3/4 tank.

Author:  LouC [ Fri Jun 18, 2021 11:57 am ]
Post subject:  Re: Fuel range on a 1988 sundowner 215

If its a 4.3 V6 with a Quadrajet, those are pretty economical. I never took mine on long trips but found that cruising just on the primaries it was very economical.

Author:  cjp555 [ Sun Jun 20, 2021 9:27 am ]
Post subject:  Re: Fuel range on a 1988 sundowner 215

Thanks for the inputs. Follow up question. Full disclosure I have extensive sailing background, I know little about I/O power boats. I was given this boat in pieces.

The Question
I see the speeds at 3k rpm above and my Sundowner runs at about 10mph at 3k rpm and 21 at 5k rpm. She doesn't plane until about 4.5k rpm This seems high to me. I have a 17" propellor. Is there something I am missing? Is my outdrive running improperly?

Author:  Surface Interval [ Sun Jun 20, 2021 8:57 pm ]
Post subject:  Re: Fuel range on a 1988 sundowner 215

Something doesn't add up. I would recommend to start by verifying that the tachometer is accurate. I believe the recommended maximum full throttle rpm for that boat and engine at top speed is 4400-4800 rpm. The engine manufacturers recommend propping it for the top end of that range (4800 rpm). Lou and others can give you a lot more accurate numbers for props and what speed to expect with that boat. You said that you got this boat in pieces. That makes me wonder whether you got a different outdrive with a different gear ratio. According to Four Winns Fast Facts, that engine and outdrive combination came with a 1.68 : 1 gear ratio in the outdrive for the 215 Sundowner. There should be a data plate on the left side of the outdrive that says what gear ratio is installed. Hopefully the data plate is still there and accurately identifies the gear ratio for the installed gear set. The input driveshaft should turn 1.68 revolutions for one revolution of the prop. You would probably need to pull the outdrive to verify this. I did not find what propeller Four Winns used originally for that boat. Generally, changing 1 inch of prop pitch will change top end rpm approximately 150-200 rpm. Changing prop diameter will have less effect. Size and shape of prop blades can also affect performance.

Author:  LouC [ Mon Jun 21, 2021 12:49 pm ]
Post subject:  Re: Fuel range on a 1988 sundowner 215

I agree something is not right there. Even with the wrong prop (14.5x19) on mine it still planed out and turned 4200 rpm. The recommended prop that I found in some of FW’s literature for my H200 with the 4.3 was a 15x17; I tried this and got 4600 rpm, then tried a 15.5X15 and got 4900. So that’s the one I stayed with; I am willing to give up top speed to make it easier on the engine to pull the boat up on plane.
You might have the wrong gear ratio in the outdrive working against you.
My boat planes out between 2800-3000 rpm.

Author:  cjp555 [ Mon Jun 21, 2021 4:41 pm ]
Post subject:  Re: Fuel range on a 1988 sundowner 215

Ok, The RPM was incorrectly labeled. It was running 23mph 3300 rpm. It is a 5.0l v8 with OMC outdrive. The prop is a 14 3/4 x 17. I am now flushing the motor and the cooling system. The outdrive seems to be smooth.

The outdrive was not removed from the boat when I got it. The cooling system was and the electronics were a mess. I am comfortable with a GMC v8 so that didn't scare me. I have learned the cooling system and am replacing fuel filters rebuilt the carb and adjusted the ESA.

Thanks for all the input. Like I said I am a newbie to the I/O stuff and learning as I go. Haven't even started on the intererior or exterior.

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