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Old 19-11-2006, 17:09   #1
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Location: Green Bay, Wisconsin
Boat: 1976 Oday 27' Booty Call
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Atomic 4 question

Hello all,

At the end of the sailing seaon here on the Great Lakes, I had sold my Oday 23 and bought an Oday 27. The "new" to me 1976 Oday 27 has an Atomic 4 30hp motor.

I'm new to inboards and was curious on fuel consumption vs rpms and overall NM distance the Atomic 4 can take me. I have a 16 gal fuel tank and the Oday 27 is about 7,600 lbs.

Been scouring the web for info and even found some great sites on Atomic 4 repair, but nothing as of yet regarding Atomic 4 gph ratio's.

Any help would be great.

Mark R.
Oday 27
Green Bay, WI

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Old 29-11-2006, 04:05   #2
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An Atomic 4, in reasonably good condition, might “cruise” at anywhere between 0.5 & 1.5 gallons per hour depending upon your boat’s displacement, LWL, propeller, and weather conditions.

Your Oday 27 might expect to cruise at about 5.0 - 5.5 kts (in "fair" conditions), consuming about 1 GPH, hence a max range of about 80 - 88 nm [(5.5 x 16) ÷ 1] or 5.0 x 16
What you are looking for are “performance” or "torque / horsepower” curves.
I don't recall seeing any, online.

Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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Old 29-11-2006, 09:15   #3
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Atomic 4 stats

Hey there,

Thanks for the reply. I appreciate in your message showing some possibilities. I might even contact the Atomic 4 experts that supply parts, to see if they have any chart/graphs on this.

However, your reply helped shed some light on it. I didn't think an Atomic 4 30hp could consume alot of fuel per hour. As I dream of next summer, just mentally preparing for cruises, sure would be good to know my boat's max motoring range and time.

Big thanks! I love this forum and pics! Even had fun sharing the pics from Green Bay area. Wait till summer 2007!
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Old 18-01-2007, 19:51   #4
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I have a piver tri that weighs about 6000 and i get about 1gal an hr at 2000rpm now i can cruse about 7.5 knts with a clean bottom i max out at 9knts but put me in a blow and it takes all i can do to go 3kn if there is 6ft waves. so it depends but i have 19gal tank and if i go 10hrs i look for gas next after noon and i carry a reserve.
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Old 31-03-2007, 09:17   #5
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A-4 Gas Consumption

We have a Catalina 27 with the A-4, but no tachometer.

Normally we cruse about 5.25 or 5.5 knots and burn around 1/2 gallon per hour. At hull speed we burn about 0.75 gph and in bad weather & rough seas we can burn in excess of 1 gallon per hour. These numbers have held up over the last 400 hours of engine time.

We usually cruise at the slower speed to extent our range (10% speed reduction gives us 50% more range).

For better starting and lower gas consumption I suggest you adjust the carb carefully to run as lean as possible, this will also help prevent carbon fouling on the plugs. Fouled plugs are not uncommon with the cooler operating temps of an a-4 using the 140 degree thermostat. You should also do an annual tune-up. It is especially important to clean or replace the points and plugs.

Fair winds with the new iron genny!

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