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Advice for new Atomic 4, gas, owners

41K views 56 replies 27 participants last post by  boatpoker 
#1 ·
We just purchased a 1978 Catalina 27 with a gas atomic 4. The boat is in very good condition, and has been well maintained.

I've read through a number of threads in this section regarding the gas atomic 4. There's some real back and forth on this engine!

On the one hand, there were posts, such as one from a surveyor, who commented that the atomic 4 on boats he's seen scares the hell out of him. That's not real confidence inspiring for us! And, is the nickname for the engine, the atomic bomb? Isn't that just great ;)

On the other hand, there are atomic 4 owners who say it's a simple, reliable engine. Though, they also recommend being careful to check for fumes -- turning on the blower and sniffing... and getting a fume sensor?

Well, we really like our boat, but we want, of course, to take appropriate safety measures. And, we'd like to have a realistic and balanced perspective. How risky is this engine? What is the appropriate perspective? What are the best practices regarding its use? Should we get a sensor? If so, what kind and where do we get one?

We plan to be diligent and follow best practices. And, now is the time for us to learn and begin to practice them. Thanks!
 
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#28 ·
Galley fires? Sure, had two kitchen fires nearly burn down my building (thank you, neighbors) in the last two years. Alcohol fires on boats? Well documented, and personally I can eat cold food and skip my coffee for days if the only heat source is alcohol.

IIRC gasoline is considered a "low explosive" because it deflagrates, as opposed to a high explosive. Bear in mind that diesel fuel is generally considered less explosive than gasoline--but diesel is the key to an ANFO hyperbaric bomb.

Aircraft and cars also do explode--fueled by just gasoline. Hollywood FX not required. Octane boosters just slow down the rate of propagation in the flame front, and STEAL POWER from the fuel. The good lord invented them to fool the masses into paying more for worse fuel, before gasahol was invented.

I like my gasoline like my women--able to make loud violent noises with little provocation and for loong periods of time, but only in the right times and places. Oh, wait a minute...maybe I've got something confused there. (VBG)
 
#29 ·
Octane boosters just slow down the rate of propagation in the flame front, and STEAL POWER from the fuel. The good lord invented them to fool the masses into paying more for worse fuel, before gasahol was invented.
Nope, he invented octane so we could have high compression engines with lovely, crisp throttle response.:cool: Slowing down the flame front with high octane may "steal power" in some sort of lab experiment but in the real world it allows you to boost the compression ratio or the boost level in a turbo or supercharged engine. On average, each point increase in compression is good for a 4% boost in power - going from a typical 9.0 to 1 to a "good old days" 12.5 to 1 gives a 14% increase in power - not exactly "stealing power" or "fooling the masses". :)
 
#30 ·
Folks have been taught to think "high test" will make their engines run better. Ignoring the new ones with detonation sensors, that's been fooling the masses for over 50 years.

Using low test to run a high compression engine? Sure, that's one way to do it. Or you can start with building a stronger engine.<G> Many ways to skin that cat. The faster the "boom", the faster the pistons can move, and velocity buys more power than just increasing the mass. That's why aluminum baseball bats hit further than wood.
 
#31 ·
Two problems with that;

1. Detonation sensors work by dialing back timing advance - that really DOES steal power.

In addition to decades of hot rodding, I am also speaking from very recent experience with my wife's supercharged Jag. Obviously it requires high octane, as specified in the owners manual but it didn't specify an octane. Since 92 is the best available in the States, I figured 91 would be O/K here.

It was demonstrating some less that stellar performance - exactly like too little timing advance - it was "lazy" on hard acceleration. I tried some 94 octane that Chevron sells here and problem solved. The computer was dialing back the timing to compensate for the inadequate octane. So much for "stealing power". I expect the car would barely run on low test.

2. You can't BUILD an engine that can withstand detonation - even diesels don't actually detonate. They are fired by compression heat but the fuel is introduced so it burns, not explodes. You'd need solid pistons and engine blocks to even come close to being strong enough. Ask any race engine builder - they routinely run 14 to 1 and 15 to 1 cr's and have to use 115 octane race gas.

You have to use the octane your engine requires. Most cars require only low test and anything higher is just a waste of money but if the engine needs it you HAVE TO use higher octane gas.
 
#32 ·
An echo to Sloop's comment above; today's high performance vehicles don't have timing "systems" they have timing "computers". It's a good thing in overall performance, and something such as octane levels in fuel makes a big difference.

As to the age old, "Atomic 4" issue, I've got a diesel now, and quite frankly, while I've had no issues "yet", I'd much prefer to be working on a gasoline motor, as opposed to this one simply because I'm more familiar with them. And having operated or been exposed to gas powered boats or 40 years, it's all about being "smart" when it comes to any of the systems. You can drown, electrocute yourself, impale yourself, explode, catch some form of plague, etc. etc. etc. Not to lessen the need for operating a blower, but it's wisdom that saves more lives than fuel type.
 
#33 ·
As to the age old, "Atomic 4" issue, I've got a diesel now, and quite frankly, while I've had no issues "yet", I'd much prefer to be working on a gasoline motor, as opposed to this one simply because I'm more familiar with them.
It actually goes deeper than familiarity. Shade tree - or should I say dockside? - mechanics are unlikely to have the knowledge, skills and tools to work on high pressure fuel pumps or injectors. They are far too precise to respond to amateur efforts. In contrast, working on an A4 is a lot like the old saying about Chevy's - "All you need is a 9/16ths wrench and a hammer".
 
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#34 ·
I have an A4 in my Catilina 27. The first year was difficult. The boat had been stored for several years so there was dirt in fuel lines and corrosion on electrical switches. I was usually single handing so when there was a problem I was unable to sail the boat and trouble shoot the engine at the same time. (I chose to sail the boat.) Finally I found a mechanic who came to the boat and together we got it working just great. It needed a new fuel pump (went electric), new coil, carb cleaning, new fuel lines and filiters, new alternator belt and a general clean up. No wonder it was a problem at first. It will receive regular maintence from now on at least while I own it. Runs smooth, quiet, and has lots of power for this boat.
 
#35 · (Edited)
I know this post is old but people still drop in to read it no doubt so I'll give ya my 2 cents here as a Navy Snipe who worked on diesels and gas engines both large and small at sea. First off, gasoline engines eat a LOT of fuel. Probably near twice what a diesel eats with the same load. However, by cruising at 4kts in a small sail boat as opposed to the more traditional 5kts the A-4 will do a LOT better. in most hulls.
Next up; Octane is increased to SLOW the burn rate of gasoline, not increase it. Only engines with carburetors can benefit from this, electronic fuel injection will just meter it as it would the lower octane fuel the engine was designed for and drive emissions up. SOME old engines can in fact pay back handsomely by keeping octane levels at 89 vs 87.
Next; A 5 year carburetor rebuild cycle is over the top, a 10 year cycle is more realistic unless poor fuel consumption or performance issues arise.
Next; Most people do not have nor can they afford or even want the specialty tools needed to work on diesel fuel systems. Compression gauges for diesels are not cheap either and getting a proper warm engine compression check out of a diesel can be a difficult proposition for even an experienced diesel mechanic.
Next; Most people keep enough gasoline aboard for their dinghy outboard or portable generator to blow many boats up many times over anyway. Insuring good quality fuel lines and fittings and having and using a fuel shut off valve in addition to purging the bilge with the blower for a few minutes prior to engine starting is not rocket science, it's common sense. Incorporating a relay that will prevent the starter from engaging unless the blower is running is the best way to insure that blower is always turned on prior to starting the engine.
Next; As mentioned, diesels are LOUD, more expensive in cost AND labor to maintain, more expensive by and large to repair, and have no real HUGE dependability numbers over any A-4 that is well kept with a modern electronic ignition module installed. The largest draw back with the A-4 is that iff your alternator goes out, you're on your batteries time as to engine shutdown from ignition system power failure. This can be 4-5 hours with a decent sized house bank mind you.
Next; Replacing an A-4 in like a tartan 34c with a diesel ALSO entails extending the prop shaft and adding a strut to make clearance for the large prop needed to compensate for the gear reductions common in those conversions. So now the cost to do that conversion just went up a few more boat bucks.
Next; If anyone actually motors enough to think the fuel savings over the lifetime of their ownership is going to offset the cost of an A-4 to diesel conversion, you should not have bought a sailboat alright? As for the conversion adding anything to the re-sale value of teh vessel, most are doing good to see even 40% of the cost of their conversion come back to them on re-sale and it will far more likely be even less.
Next; There were over 40,000 A-4s put into small sailboats over decades of manufacturing. Over half of those are still running and many running very fine still with no major overhaul after 45 years. Most of the diesels that were offered as options are long gone or unable to run because of parts acquisition issues. The Ferryman 2 cylinder unit is one of those. Those were used as options in many of the boats that came standard with A-4s very few are still running.
Finally; The only GOOD reason I can see for replacing an A-4 with a diesel is to increase motoring range. If you are satisfied with the motoring range of an A-4 odds are you would do well to keep it even if that entails a major overhaul including the transmission. An overhaul such as that once the engine is pulled out and on the shop bench can usually be accomplished for around 1400 dollars at most with simple hand tools. Most can be brought to new running performance on under 1000 dollars. Few A-4s to date have needed any over-bore work because the low compression is gentle on the cylinders. A simple honing with a low speed hand drill and a proper size hone is all that is generally needed there on the first overhaul. Even if the new ring gap runs a few thousandths over spec, so what? 44 years more service instead of 45? Many of these engines can and no doubt will live to be 100 years old and still be running. It will be interesting to see how many make it to that 100 year mark, where then, they will without a doubt be very cherished museum pieces if nothing else. As far as those yards wanting 8k to overhaul an A-4 goes,,,,pfffft
 
#36 ·
a belated welcome to the site Navy! One thing about all this gas vs diesel. Knowing how careless many recreational boat owners are.. it's amazing they don't blow up just gassing the family car, much less have a boat with such explosive potential.
A4s are great. so are diesels. I love the later had one in my boat.

I don't think I've ever been around a gas engine boat and not smelled gas. when they are dock, running, passing by underway. Stink! seems to be ok and acceptable.. yet the slightest hint of diesel smell... gotta find it.
 
#37 · (Edited)
The issues with the diesel smell factor here are more to do with how a single ounce of diesel fuel in the bilge can stink for weeks. A little gasoline in the bilge while no doubt an explosion hazard of greater dimensions is gone in a few minutes with the blower running. The engine exhaust issues are little to nothing, that's one of the reasons we got a sailboat to begin with correct?
 
#38 ·
The "Atomic Bomb" myth is an urban legend that just won't die.

1. Your galley stove is way more dangerous than an Atomic 4.
2. From the late 1960s through the early 1980s, nearly every production cruising sailboat made in North America came with an A4. How many of them have actually exploded? I'm guessing that methane gas explosions in city sewers are more common than A4 explosions.
3. There are a ton of power boats with gas inboard engines produced today (obviously not with A4 engines, but big gas engines)...
4. ...and there are even more outboard-powered boats with internal fuel tanks sold today. How big do you suppose the fuel tanks are on one of those 500 hp + center console rocket ships that are so popular in Florida?

The point is that gas engines have gotten a bad rap, and the A4, in particular, has been treated unfairly. As with any engine, as long as it was well-maintained, I would have no apprehensions about buying a boat that had an A4.

To put the little A4 into perspective:

This Grady White has a maximum horsepower of 1050 (in 3 gas outboard engines) and carries 344 gallons of fuel. It also has a diesel generator.
Grady-White | Express 370 Express Cabin

This 35' power boat has twin gas inboards (stern drives), a gas or diesel generator, and over 200 gallons of fuel capacity
Build Your Sea Ray Boat

Look at the horsepower on these boats and think about the size of the gas tanks needed to keep them fed.
https://yamahaoutboards.com/en-us/
 
#39 ·
Don't care. About anyone's choice of engines or fuels.

As I stated above. Both diesel and gas engines are great for boats.


Is the flat-out stupidity and laziness of people, that causes explosions and fires.
 
#40 ·
Thanks for the summation, NavySnipe. I agree with everything you stated. I was glad to have an A4 in my last boat. I am now glad to have a diesel engine with the possibility of further range. To get the same range out of a gas engine I would have to either give up valuable interior volume, or put lots of jerry cans on deck (which will raise the center of mass of the boat or be torn away in a storm).
 
#41 · (Edited)
The atomic 4 is a sturdy little engine and is not problematic in itself however the vast majority (I really mean .... all) of manufacturers who installed these engines were complete idiots.

In 4,593 surveys I've never seen a single Atomic 4 properly installed.
The issues ...

The back side DC fuse and or breaker panels and AC breaker panels and AC outlets exposed to the engine/fuel compartment.

AC outlets in the engine/fuel compartment.

Solid core copper AC conductors.

AC connections made with wire twist (marrette) connectors ( in the engine/fuel compartment and elsewhere).

Solid copper fuel lines with no means of vibration control.

Non-ignition protected battery chargers or even worse chargers that were marked "protected" but were not.

Solid copper AC conductors.

Failure to bond the DC negative and AC grounds.

AC fuse panels instead of breaker panels.

Battery chargers mounted directly over batteries.

Unfused positive conductors on batteries.

A total disregard for the proper ventilation (intake and output) of a compartment containing gasoline with some models even venting directly into the accommodation spaces.

AC conductors zip tied to DC conductors and in some cases various parts of the engine.

Propane hose and/or solid copper pipe run through an engine compartment unsecured or not protected from vibration.

Gear clamps used to make propane connections.

Multiple propane connections (and in some cases valves) located within the accommodation spaces or engine compartment

I have seen these issues in every brand in North America that installed these engines.
 
#42 ·
The atomic 4 is a sturdy little engine and is not problematic in itself however the vast majority (I really mean .... all) of manufacturers who installed these engines were complete idiots.

In 4,593 surveys I've never seen a single Atomic 4 properly installed.
The issues ...

The back side DC fuse and or breaker panels and AC breaker panels and AC outlets exposed to the engine/fuel compartment.

AC outlets in the engine/fuel compartment.

Solid core copper AC conductors.

AC connections made with wire twist (marrette) connectors ( in the engine/fuel compartment and elsewhere).

Solid copper fuel lines with no means of vibration control.

Non-ignition protected battery chargers or even worse chargers that were marked "protected" but were not.

Solid copper AC conductors.

Failure to bond the DC negative and AC grounds.

AC fuse panels instead of breaker panels.

Battery chargers mounted directly over batteries.

Unfused positive conductors on batteries.

A total disregard for the proper ventilation (intake and output) of a compartment containing gasoline with some models even venting directly into the accommodation spaces.

AC conductors zip tied to DC conductors and in some cases various parts of the engine.

Propane hose and/or solid copper pipe run through an engine compartment unsecured or not protected from vibration.

Gear clamps used to make propane connections.

Multiple propane connections (and in some cases valves) located within the accommodation spaces or engine compartment

I have seen these issues in every brand in North America that installed these engines.
With the exception of the the fuel hose and ventilation concerns, I fail to see what these have to do with the installation of an Atomic 4 (or, really, any) engine. These are problems with electrical or propane installations which have little or nothing to do with the motor.
 
#48 ·
It's a myth that the A4 was a marinized tractor engine. It and its ancestor were designed and built as marine engines.

The Universal Atomic 4 is a four-cylinder, 64.46 cubic inch, 30 horsepower (22 kW) gasoline engine produced by the Universal Motor Company between 1947 and 1984 for use as auxiliary power on sailboats.

Universal Atomic 4
History and Lineage

The Atomic 4 is descended from an earlier Universal Motor Company design called the Utility Four, which was used extensively in World War II by the United States Navy and allies to power the lifeboats for the ships, barges, and tankers of many navies and merchant marine fleets. The Utility Four model was replaced by the Atomic 4 in 1947.
 
#51 ·
I'm not a fan of gasoline engines on boats. Yes, the probability of an accident is low, but it's lower with diesel.

I had a fuel line fail last year that would certainly have led to a fire in a gas engine. Instead I just had a big mess, and a firm appreciation of the shortcuts the previous owner had taken. (re-inspection of the engine resulted in a few other preventative fixes as well.)

But since you have it, and probably don't want to spend $10K repowering it, diligent preventative maintenance is the key. If you have managed to avoid lighting yourself on fire at a gas station your whole life, you have the skills and sense to manage this application too.
 
#52 ·
$10K to repower with diesel?

Lots of luck. The engine on a pallet will be all that or more unless it is the smallest available.

Just the incidentals will be a big chunk of that. Fuel tank, fuel lines, fuel filter, new or modified engine beds, maybe shaft, prop.......
 
#53 ·
I have had 2 boats with A4 engines......my current one is in my Irwin 32....It's a gas engine so run your blower for 10 minutes before you start the engine, no different if you had a sedan with twin chevy big blocks. Most important is to install a combination fire/carbon monoxide detector in you cabin or engine compartment (maybe both). The engine is very reliable and will serve you well if you do your research on maintenance procedures (try Youtube, plenty of posts) your best source of information can be found at Moyer Marine. If you own an Atomic 4 that is your starting point!!!!!! There were over 40,000 of these reliable little engines built for marine power and there are still many of them still in use today.....
 
#54 ·
I have had 2 boats with A4 engines......my current one is in my Irwin 32....It's a gas engine so run your blower for 10 minutes before you start the engine, no different if you had a sedan with twin chevy big blocks.
Your chevy sedan does not trap fuel leaks or fumes inside it's hull where a myriad of non-ignition protected sources of sparks lie in wait.
 
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