Atomic 4 fuel economy

[grumol]

doing a search, i came upon a message string re:the Atomic 4 fuel economy -- noticed a post stating 1/4gal/hr. -- was very surprized, as that is what i hear a diesel gets -- my experience with several auto diesels has been close to double the fuel economy, so i expected to find this in marine applications -- is anyone else out there getting this fantastic fuel economy in their Atomic 4 -- if thats average, then i''ll leave the engine in the boat i''m looking to buy, rather than replacing it with a diesel -- thanks, bob

[thomasstone]

Bob, that does not sound right. You can type atomic four into google and there are plenty of forums or contact Moyer Marine.-thomas

[tumbleweed35]

At a little above idle speed my A4 pushes 13,000 disp at 3.5 kts and uses .5 gal per hour. Increase speed to 4.5 kts and use between .75 and 1 gal per hour. This is with a three blade 12x6 prop

[Irwin32]

At cruising speed - no way. At 1700 rpm I use slightly over 1 gal per hour with a CDI 2 blade prop and 12,000# of boat in smooth water. If I push the rpm up to about 1850 my gas use spikes to maybe to 1.5 gal per hour.

I am interested to know what other A4 users are getting as they push their rpms up to close to 2000.

Manuals that came w/engine don''t recommend running that high, but Moyer Marine says to do it.

[ahld]

My Northstar 38 cruises at 6 mph @ 3/4 gal. hr. Tops out at 8mph, no idea of the burn rate at that speed, tho'.

Dave

[nolatom]

I remember about a gallon an hour with that engine ("all the technology of a Model-A Ford") on a buncha boats (like the Cheoy Lee Bermuda 30) back in the day.

1/4 Gal per hour is what I get now on a lightweight Beneteau 7.5 skiff with a 4 hp one-cyl Yamaha outboard. Not bloody likely with an Atomic 4 on any boat, I wouldn't think.

[Valiente]

Originally Posted by tumbleweed35

At a little above idle speed my A4 pushes 13,000 disp at 3.5 kts and uses .5 gal per hour. Increase speed to 4.5 kts and use between .75 and 1 gal per hour. This is with a three blade 12x6 prop

I've measured this closely and with a 33 foot, 10,000 lb. fin keeler pushed by a 12 x 6 fixed prop AND towing a Zodiac at 5 knots cruising speed (about 1,700 RPM at a guess), I used 0.73 Imperial gallons per hour, which is about 0.875 U.S./hour.

Had I dropped to 4.5 and took the Zodiac off the stern, I estimate I would have gained about 0.15 Imp gal/hour. I used these figures to determine that I could replace the original 15 Imp. gallon Monel tank with an 11 U.S. gallon Tempo tank and could gain needed locker stowage and shed weight. My range is cut by approximately 1/3, but if I am cruising, I can carry 5 gallons of jugged gas and solve that problem as needed. Frankly, if I only day-sail, I have difficulty using up a single tank in a season just motoring in and out of my basin...which is why an A4 makes a lot more sense than a small diesel when you motor two-three hours a month! Diesel HATES that kind of light duty use.