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post #11 of 27 Old 06-30-2013
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Re: Atomic 4

wondering.. your looking at fairly old boats.. is it a budget question? I'd go for diesel, never had one until now, and have grown to love the little thing chugging away hour after hour. Also think about size of boats your seeking. Almost as soon as you buy one you will a larger one.... but then maybe not ..."jus saying"

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post #12 of 27 Old 06-30-2013
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Re: Atomic 4

Originally Posted by TQA View Post
If all you want the engine for is to push you in and out of the marina then an A4 is fine.

However if you want to use it for long periods of upwind motorsailing then I would go for the diesel.

You don't see many A4s in the Eastern Caribbean.
True if the A-4 is tired with low compression but I have run my A-4 for 7 to 8 hrs a day, day after day for weeks running the ICW. Even a 26 hr nonstop run back from the Abacos. I wonder if the size of the boats you usually find A-4s in is more the reason that there are few in the E C. Dan S/V Marian Claire

Last edited by marianclaire; 07-01-2013 at 07:12 AM. Reason: Sp
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post #13 of 27 Old 06-30-2013
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Re: Atomic 4

We have an A-4. Simple, reliable, relatively quiet and safe. Our boat has a 20 gal fuel tank. The engine pushes the boat at about 5.5 knots, with no sails up, burning 3/4 of a gallon per hour. (With sails up we can cut the fuel consumption in half and still have the advantages we were running the engine for.) These are rough averages and are on the conservative side. That gives us about 30 hours of motoring with a 10% (reserve) on a full tank of gas. There are seasons we don't use the engine 30 hours for the entire season. It is a sail boat? Granted cruising in remote places we carry another 10 gallons of fuel. It has never been necessary to rely on that 10 gallons. We use it up if we need to top off the tank but that has always been instead of making the effort to buy gas along the way. Gasoline is available everywhere! So. With a little motor sailing thrown in and a couple of 5 gallon jugs we have an effective cruising range of 200 to 300 miles. It isn't a particular handicap for us when it comes to cruising range. I have never motored for 30 straight hours with no sails on our boat. Delivering another boat where the schedule is paramount it isn't unheard of.


Islander-28, Marshall Sandpiper

Last edited by downeast450; 06-30-2013 at 03:15 PM.
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post #14 of 27 Old 06-30-2013
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Re: Atomic 4

I read alot of posts on this site regarding gas or diesel. Perkins or Yanmar, etc. etc.
I think the most important thing to look at, besides condition, is easy access to the engine, transmission, stuffing box, electrical system etc.
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post #15 of 27 Old 06-30-2013
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Re: Atomic 4

Originally Posted by travlineasy View Post
Where do I start first? First and foremost, the A4 is very reliable, extremely efficient, easy to work on, rugged, and cost efficient. When it comes time for total replacement, you could install three A4s for the cost of a similar HP diesel.

As for diesel being more fuel efficient than gasoline - not when you compare HP to HP. I'm pushing a broad-beam, 15,000-pound plus Morgan 33 O.I. with a 30-HP A4 gasoline. I get about 9 MPG at 1,800 RPM and cruise at 6 MPH on calm water. I have a friend with a similar boat, a Morgan 321, powered with a 3GM30 Yanmar Diesel. The boat weighs less, has a narrower beam and his fuel efficiency and speed are not as good as my A4. And, when it comes to repairs, the cost of replacing that Yanmar is out of this world.
These statements are just not correct. Moyer charges about $5000 for a rebuilt direct drive A4. I bought a rebuilt Universal 5411 diesel (with the transmission) for my last boat for about $3000. A larger rebuilt Universal or Yanmar would be in the $4000 to $5000 range. Pretty much a wash.

A gas engine is NOT as efficient as a diesel if you compare the same horsepowers. At the same POWER, a diesel will consume about 30 to 50 percent less than a gasoline engine like the A4. Really has to do with the diesel's high compression ratio and fuel injection vs the gas engine's lower compression ratio and poor fuel-air mixtures with a carburetor.
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post #16 of 27 Old 07-01-2013
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Re: Atomic 4

I will say that I have looked at hundreds of boats in person and a whole lot more on the internet and never saw an A-4 with a saildrive unit on it. If you have found two of them then you have strange luck, LOL. I would stay away from any OMC SailDrive boats, the thing just really is not a happy setup.

If it is just an A-4 with a regular transmission and shaft set up then comparing the diesel powered boat to the gas powered ones I would go for the one that I thought best met my needs and desires with one exception, if you are planning on making longer blue water passages, I would recommend the diesel, it will be more fuel efficient and it will have far higher torque to fuel ratio, meaning it will move the boat better for less fuel.

Any used sail boat should have the tanks purged, the lines purged, and the fuel system serviced unless you are 100% positive that it has not been sitting without having proper maintenance done on it regularly. Replacing all the little fuel lines and hoses that look to be brittle, dry, or just suspect will save you a ton of money and headaches in the long run.

If you get a diesel you will be well advised to set up a multistage filter for fuel polishing if your boat does not already have it, and it does not hurt to do the same with gasoline. Clean tanks, clean lines, and clean fuel will help keep any engine running well a lot longer.

I hope you get the boat you want at a good price and that you enjoy it for a long time to come.


It is good to learn from your mistakes, but much better to learn from the mistakes of others...
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post #17 of 27 Old 07-01-2013
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Re: Atomic 4

I have a A4. I like my A4. However, I think you will find that a boat with a diesel will have a higher value (all else the same), for the reasons stated.

Bristol 27
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post #18 of 27 Old 07-01-2013
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Re: Atomic 4

I had a A-4 on a Sabre 28 for 22 years and a Yanmar 2gm on a C&C for 4 years. Both have pros and cons. If the Yanmar is FWC then it is a big plus. If it is the one cylinder gm10 or gm8 you won't like the noise and vibration. An 81 Mirage 27 probably has one of the last A-4s built. Provided that all of the engines are in good shape here are some things to consider: the Northern is a bit pinched in the ends and would be a little twitchy with a following sea. The Marine 28 is similar to a Sabre 28 and potentially is the fastest of the bunch. The Mirage is a bit slower than the Mariner. All 3 could be an acceptable first boat depending on their condition and your maintenance skills and/or resources.
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post #19 of 27 Old 07-01-2013
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Re: Atomic 4

I've had both and they're both fine as long as they're in good shape.

Short answer is that there's no reason to rule out an A4. You should make the decision based on the quality of the boat and engine, not on the nameplate in this case. In fact, depending on the model, I might rule out the Yanmar - I had one of those little one-cyl 10hp jobbers and it sucked. Loud and underpowered. A4s can work fine if they've been well-kept and judiciously upgraded. They can be a real pain in the ass if not - but that's true of any engine. Parts are easy to come by and relatively cheap.

Unless one of the engines is in really good (recent rebuild or repower) or really bad (in need of work/rebuild) shape, or if the Yanmar is one of the small 8-10 hp models (not enough for a 28' boat), I'd consider it a tossup and make your decision on other grounds...
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post #20 of 27 Old 07-03-2013 Thread Starter
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Re: Atomic 4

Thanks All,

Gary your comments are appreciated. I made a mistake in my original posting. The sail drives are c/w omc inboard.
My price range is anywhere between 5k and 9k. Any of the boats we have looked at are for their age, priced right or the owners truly believe they will get their inflated price. The cosmetics don't really bother me, it's the mech. and struct. issues that I don't want.
I'm glad to hear different opinions on gas vs. diesels and glad not to hear of any explosions either. You really can tell those owners who maintain any of their equipment?
The way some folks show their boat is truly questionable!

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