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Old 05-01-2006, 13:48   #1
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Lifespan of an Atomic 4

The '73 C&C 27 we're considering has an original Atomic 4 engine. The meter says it has just over 2700 hours, and the current owner has had the boat since '91 and has cared for the engine well. The owner before him apparently did so as well.

Each year, the current owner has done a compression check to monitor the engine, and one repair he did was to replace the head gasket (do to a leak between two of the cyclinders). I haven't asked yet if he had the head checked for warping when he did this. He also installed four new guages for the engine this year.

The boat comes with a 12 gallon tank, and I heard that some Atomic 4s can drink as much as a gallon an hour. For an offshore trip, he took close to 15 gallons of additional fuel in portable tanks under the cockpit seat... The boat also has a newer Martec folding prop.

So, the question is this-- what is the lifespan of an Atomic 4 that is cared for well? I've read several sites about them, and some mechanics like their simplicity and relative low costs of repairs and parts, but I have heard warnings about their reliability in bad weather. Also, even if the engine passes the survey with flying colors, I've heard that significant problems can appear in a hurry.

We'd rather not repower now or in the near future, and we'd follow all service and maintenace recommendations if we took on the boat. I've also rebuilt car engines in the past, so a gas engine would be familiar.

Thanks in advance!

Jim H
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Old 05-01-2006, 14:53   #2
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For an offshore trip, he took close to 15 gallons of additional fuel in portable tanks under the cockpit seat...
Uh, don't do that.
A small leak could fume up the bottom of the boat and any spark, or engine start could be your last....

Keep all gasoline OUTSIDE.....

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Old 05-01-2006, 17:31   #3
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How long will it last? untill it dies....sorry just had to.

Realy, I think 5000 hours is achievable.
Again, why? it's a time bomb. The cost of repowering with a reliable diesel is well worth the peace of mind of no fires.
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Old 05-01-2006, 18:31   #4
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For reliable life span, 3000 hours is about it. That being said, an A4 will run and most of the time, run well, until the heli coils that are holding the heli coils for the head bolts no longer have any solid metal to bite into. 5000 hours and more is not unheard of.
That being said, weather you want to chance pushing that last 300 hours out of the engine is a matter of what you are comfortable with. If you plan to use the engine for anything besides in and out of marinas, I think a repower is in your future.
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Old 05-01-2006, 21:03   #5
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The lifespan of an Atomic 4 is not measured in hours run but in how much of the internals of the block have corroded away.
How to measure how much 'meat' is left: Drain the engine if fresh water cooled, then remove one of the exhaust manifold bolts; with a dental pick, etc. reach into the bore of the bolt hole and count how many threads are left - if 4 or more threads than you have enough/sufficient casting thickness for quite a few hours. Less than 3-4 threads, the engine has corroded away internally and isnt even a candidate for a 'rebuild'.
(Reseal the end of the manifold bolt with aircraft grade 'Permatex' when replacing to seal the bolt/threads.)

An Atomic-4 that would be a 'keeper' or a 'good find': Has freshwater cooling (heat exchanger) ... meaning that the boat was stored with the engine ***never drained / dried-out**** but had antifreeze with rust inhibitor in all the cooling jackets and exhaust manifold ... prevents the formation of internal 'slab rust' and protects the 'good' / blue or black rust and prevents the change to bad: 'red' rust.
One that was run often and hard; not, one that 'sat around'.
One that had 'hardened valve seats' installed ... to handle the 'hammering' caused by unleaded gasoline ... this engine was designed for leaded gasoline and unless the PO used a 're-lead' compound you can expect the valves and seats to be quite 'hammered' no matter how many hours on it.

If the current compression is good and the internals arent showing much corrosion, then ~4000+ hours is a fair amount of time. They dont 'wear out' as much as they 'corrode away' from the inside out.

A top-of-the-line, precisioin rebuilt A-4 would run about $4500; $3500 for a 'short block' .... the install labor is extra but its easy to do yourself. go to www.moyermarine.com for prices and options ...this is the website of probably the world's recognized 'guru' of Atomic-4s.

If it doesnt already have these then consider to add: electonic ignition with compatible ignition coil, electric fuel pump, PCV valve, heat exchanger, new external thermostat housing.

A diesel conversion: $9-11000 engine, $1-2000 bed rebuild, $300 new shaft and prop, $??? new tank and fuel delivery system ... add labor ... probably about $14000 when you're done. And the boat will SQUAT on its stern with all that extra added weight of a diesel.

***** Make SURE that this boat does NOT have a fiberglass fuel tank. As the USA changes over from MTBE to Ethanolated gasoline severe problems are showing up in marine engines, etc. 1. most old (pre mid 1980s) fiberglass fuel tanks are INCOMPATIBLE with ethanolated gasolines ... will dissolve the resin and the tank WILL leak ..... BOOOOOM!. 2. MTBE fuel co-mixed with Ethanolated gasoline forms strange 'gums', etc. and these can destroy the engine .... just like adding sugar to the gasoline. 3. The rubber components (float needle valve, gaskets, etc.) of the carburator are NOT compatible with Gasoline with Ethanol - need to be changed. Be aware that the 3/4-1 gallon per hour was leaded or MTBE added gasolines; you can expect 10-15% LESS fuel economy with gasoline formulated with ethanol.

Hope this helps.
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Old 05-01-2006, 23:02   #6
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Hence my comment about the helicoils holding the helicoils. Fortunately these engines still seem to hold together when the steel can only handle about 10 inch pounds of torque
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Old 06-01-2006, 05:20   #7
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Is it really worth installing helicoil thread repair kits for head bolts? Wouldn’t that much block corrosion be a good indicator that other problems likely exist, and you're (actually, you may have much more life left in you, than the engine) near end-of-life?
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Old 06-01-2006, 06:50   #8
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Actually these engine do not have 'head bolts' but use head 'studs'. If one does happen to tear out the base threads when removing, a new stud with a larger base can easily be machined and the old stud bore can simply be machined to a larger diameter. Studs are ripped out when someone 'hammers off' the head with wedges, etc. .... a bad practice with any studded engine. When removing the head of a 'studded' engine one should use a 'stud puller' (Snap-on, etc.) then there is much less chance of ripping the threads out. Stud bases MUST be sealed with a waterproof gasket compound to protect the threads and to prevent leakage .... or the threads will corrode.
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Old 06-01-2006, 07:54   #9
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Richh,
I counter your statement about weight. An AT4 weighs in between 300 and 350 lbs.
A current production Universal M3-20B is 254 lbs. I believe the water line will need to be lowered.
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Old 06-01-2006, 08:23   #10
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Ooooo! thats a nice engine! especially with good weight. I usually put Universal totally out of my mind when someone says 'diesel'. The older Universal offerings of direct replacment for A4s were much heavier and much much high in price. Whats the approx. in-the-crate price? Requiring no bed, etc. changes if the price is good this would be very attractive. Is that actually an OSCO manifold that I see?
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Old 06-01-2006, 08:25   #11
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Pat, what would it cost to replace the Atomic 4 with a Universal?
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Old 06-01-2006, 08:34   #12
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An M3-20B runs about 6200 in the crate, with trans, mounts, panel, harness.
Gunner, alot depends on the boat. I did an Alberg 30 last year AT4 to Univ 25XPB and it ended up about 8300

Richh, they do their own csatings. Not bought from Osco. Osco might copy it for a replacement
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Old 06-01-2006, 08:46   #13
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There is nothing like NEW power. It was the best move for me.
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Old 06-01-2006, 09:43   #14
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Wow, this is an impressive set of replies and information-- thanks to everyone (espeically for the general estimates for repower).

One important fact I left out is that the engine I'm considering is raw water cooled, but the boat has been in fresh water since '91 (except for one trip to Puget Sound in '96) and possible before as well. I have seen raw water to fresh water conversion kits for around $500, but I'd need to do an assessment like Richh described to accurately determine the internal state of the engine before deciding if the upgrade is worth it.

I've also read that fresh water cooled engines run hotter than raw water cooled ones, and this reduces carbon build up and extends the life of the engine.

The engine also has points and condenser, and I've read both great and not-so-great reports about the electronic ignitions. It's clear that they can improve the performance, but some have gone back to the points and condenser for ease of trouble-shooting. Another reported that he "fused" his electronic ignition just by accidentally leaving the key on...

The fuel tank in a C&C 27 is easily accessible, and they aren't fiberglass but I hear that they do need replacing occasionally (which is thankfully easy to do).

If this is becomes an "interim" boat for us (one we might keep for only 3-5 years), it would be tough to do a re-build or re-power just before selling it, but the maintenance has been so good on this engine that I wouldn't be surprised if it passed Richh's test for internal corrosion. In the winter, it has been filled with antifreeze and fresh water, and in season it has been well used and not neglected.

This is all good information to think about.

Jim H
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Old 06-01-2006, 12:48   #15
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Yup a raw water cooled engine should have a 135 degree T'stat or the engine internals will soon foul with carbonates (boiler scale / 'rocks') . Fresh water also contains carbonates that will drop out and form scale .... just takes longer. Most olde A4s for some reason have 180 degree t'stats whether used in fresh or salt.
The 'real' problem with raw water cooled engines is that the water will drain back and leave the engine internals 'dry' and that constant cycling causes 'bad'/red rust to form inside .... and thats the reason why the navies of the world usually keep a ships engine 'always running' or the internals always flooded. Cast iron is a good metal to use in the marine environment as when exposed to HOT water it forms (ferrous) blue-black rust ... actually becomes a protectant due to the hot circulating water that constantly circulates. the process is called: 'blueing'.
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