gallons per hour

[Kgorby]

First I would like thank everybody who replies to all the questions, the information is priceless. Now my question, moving from a powerboat to a sailboat (hull # 141) my wife is constantly worried about running out of fuel. We have an atomic 4, would you know what our gallon per hour should be.

[Alma]

Lucky you. You will find the A4 is the sailors best friend.

I burn about 1.25 gallons/hr when running hard. I also use a little oil so check yours often 'till you get a feel for oil consumption.

Check and see if you have an adjustable main jet at the bottom front of your carberator. If not, get one from Moyer marine. The original main jet runs rich- Rich is better than lean for a one size fits all configuration. An adjustable one allows fine tuning.

To set your ignition timing for best power and economy run at crusing speed and undo the lock on distributer and turn the distributer slightly to get the best speed- then turn it so you go a little slower.

A great upgrade is electronic ignition. The best is pertronix. Moyer sells it but you can do better on line.

Enjoy your Atomic 4- It is superior to any Diesel for coastal cruising. A lot of folks will poo-poo the A 4. Do not listen to them.

Good Luck!

[Dolce_Vita]

For another data point, our A4 has an adjustable main jet, electronic ignition, and a 3-bladed 15-inch prop with 9-inch pitch. 
Cruising at about 5 kts @ 2000 rpm, we get around 3/4 gallon per hour.  We have no fuel gauge, so I just track our hours of
runtime (we have an engine hours gauge) and use 1 gal/hour as a rough rule of thumb to give me some margin.

Your mileage may vary!

[Bill1188]

I have a Volvo MD 11 in my boat. Had an atomic 4 in my previous Ericson. I loved the Atomic. Easy to work on, replacement parts as close as your nearest auto parts store, and gutsy. Actually thinking of ditching the Volvo and putting in an Atomic. Anyone done that? Is it major surgery?

[selene]

Bill, we had a discussion about this on another string - can't find it as yet.  Fairly major surgery.  One of the surprise (to me) factors is diesel and gas engines spin the shaft in opposite directions.  After the engine was spec'd, Pearson factory offset the shaft to port or starboard to help minimise propwalk.  Not a huge deal, but your propwalk in reverse would be pretty bad.

So to the new engine, new exhaust, modified engine bed, modified electrics, add new propshaft, new propellor.  And (because most people don't understand how good the A4 is) reduced boat value.

:-(

[Alma]

After this question last week I revisited the ignition timing on my A4.

Being a hot-rod I always bump the timing as high as the motor likes without regard to factory specs. So last weekend I backed it off a tiny amount to see if it would decrease my oil consumption. Do any of you have the aftermarket PVC kit? I do, and although it keeps the boat and engine compartment smelling fresh- I believe it increases oil consumption. A knowledgable motorcyclist I know said engines like A4 and aircraft engines should not have PVC because of their constant load running conditions. Ideas? I can burn a quart in 8 hours if I am crashing into a head sea... There is no evidence of smoke, sheen on water or oil in bilge and spark plugs are even and clean. I know an engine with timing too far advanced will consume oil so I am not only looking for smoothness (the companionway ladder is a good gauge) but a reduction in oil consumption. I use 40W and change it at each tankful of fuel (30 hours). The engine is smooth and powerful so adding oil is only a small inconvenience.