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Discussion Starter · #1 ·
We purchased a 1978 P31 last fall. It had a mystery problem with the engine so the price we paid was a steal. We had work done on it over the winter and thought we had it licked. Turns out, after a breakdown on our way home in June, that the engine needs to be pulled to be repaired (Fractured gear off the cam that drive the accessory drive).

We've already spent nearly 1K last winter tweeking this and that, replacing the water pump, and a replacement accessory drive.

Now we are wondering if we should
1: Keep pouring money into this engine.
2: Rebuild it (we have a second Atomic 4 we can strip for parts. Although the accessory drive off we put in the boat came off this engine and it failed) Looking at up to 3K for the rebuild + 1K labour to help me with the work to re-install
3:Repower with something else.

If we change the engine the question is what?
Most sailors are recommending switching to diesel. We have researched this option a little and, as far as I can tell, we would be looking at about 3K for a used engine + 2-2.5K for labour and modifications.

A friend, not a sailor, suggested a small, newer, car or motorcycle engine if we decide to stick with a gas engine. It seems that a fairly new engine from something like a Civic or Corona could be had from a wrecker for under $500. Maybe even a small diesel from a VW Rabbit (although they are front wheel drive and that may cause more problems than it's worth). He also suggested a shaft drive engine from a motorcycle. He had many example off the top of his head that could deliver the appropriate (or more) HP in a small reliable package.

A long winded story to get to the question: Why are marine engine so expensive? And what makes them so special that a common, easy-to-get-parts automotive engine wouldn't do the job? Are marine engine made with better materials to protect them for the corrosive environment in which they work?

This is all new to me and I am a little confused!
 

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Most marine engines are built with 'extra thick' castings (block, manifolds, etc.) to allow for the inevitable internal corrosion. Hint: most marine engines never 'wear out'; instead they 'rot away' from the inside. The key here for rebuilding your A4 is to remove the exhaust header and with a probe go inside the exhaust stud holes and count the number of remaining stud threads ... if 4 or 5 threads are remaining, then rebuild; ..... if less than that amount of threads remaining then the casting has become too thin due to internal corrosion and isnt worth the cost of 'rebuilding'.

For a precision rebuilt A4 suggest you go to Moyer Marine Atomic 4 Engine Rebuilding and Parts. They even have an 'exchange block program' ... theyve secured a source of new cast iron block castings in case your old block is severely 'rotted out' internally. Lot of options and lot of upgrades available through MoyerMarine for the DIYer.

Best of all the $CDN is much 'stronger' than the very weak and 'debased' $US, so the true cost will be much less for you, even including 'import fees'.

Repowering an A4 with a diesel will usually involve total rebuilding of the engine beds, complete change out of the propshaft and prop, and fuel tank, control system, etc. etc. ... for a total final bill of ~$14K if replacing with all 'new'.
 

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What I would do in your position, is buy one of the rebuilt and upgraded Atomic 4s that are available. A quick search came up with this option :

Moyer Marine Atomic 4 Engine Rebuilding and Parts

You can also save money by just going for a reconditioned block for $3k, or for $3.5K with cylinder head.

Sure you could install a car engine, many marine engines are based on one (BMC Tempest, for example), but it has to be marinised. You have to mate it to a marine transmission, and cool it. That means an auxiliary drive for your raw water pump. You also need a water cooled manifold, heat exchanger, etc. This would be a non-trivial engineering project.

If you want to go sailing in the near (or even distant) future you'd be best off with a replacement engine.

The option to replace with a diesel isn't bad, but you'd need to find a good one. That's the problem. Lots of people with dead diesels are also looking for a good one. My Universal 5424 is going fine, but while you can get the core Kubota engine, the marinisation parts are getting really hard to find. That means even if you do find an engine in great shape that's 20 years old, it might only have 10 useful years left before it's obsolete.

My neighbour had his Atomic 4 fail. Guess what he just replaced it with? Reconditioned Atomic 4.
 

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For got to mention re: winterizing any marine engine. Never ever drain and leave the block/manifold filled with nothing but air for long term lay-up. Doing so will GREATLY accelerate the internal rusting of the cast iron. Instead, fill ALL the cooling passages with a mixture of EthyleneGlycol antifreeze (usually contain anti-rust compounds) and freshly Boiled/DISTILLED water.
 

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Discussion Starter · #7 ·
Thanks for the quick responses.

How to assess the amount of internal corrosion is great help. We were wondering how to determine if the block was worth using.

As far as "marinising" an automotive engine: Cooling - does it have ainstall a water cooled heat-exchanger? Would the radiator (strategically placed) not be sufficient to cool the engine?
 

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Why don't you close off the accessory drive. They have a tendency not to receive enough oil. Even a modification can be done so they do get enough oil. This forum tells you how to.
Some engines don't use them. They run the alternator off of the front of the crank shaft.

The Atomic 4 can run without an alternator, off the battery for an hour. Have two batteries. Even a
gas generator.

This way you could use up the money you sunk into the engine
 

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Repowering an A4 with a diesel will usually involve total rebuilding of the engine beds, complete change out of the propshaft and prop, and fuel tank, control system, etc. etc. ... for a total final bill of ~$14K if replacing with all 'new'.
It sounds like a diesel re-power would be more than you want to spend. But if you want to get an idea what the cost would be for your boat - and what exactly your boat would require check out Beta Marine. They have direct replacement diesels for Atomic 4's here. According to their site they even have Atomic 4 mounts so you don't have to change out the engine beds.

You'll get lots of opinions as to how much horsepower you need. We have a 25hp diesel in our our 30 and I wouldn't want to go down in power. Others will disagree. But if you go with anything other than an Atomic 4 the prop MUST be correctly matched to the engine/trans. A prop shop can do this.

If you end up seriously considering Beta Marina you might try PM'ing Donna Ferron (screen name DRFERRON). If my foggy memory is right she put a Beta Marine diesel in her Catalina 30. She could probably fill in some blanks for you.

Best of luck. Whichever way you go a re-power is a big job. And don't forget to add some stretch to the budget for all the "while I'm in here I might as well replace this" items.
 
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The cost effective approach is certainly to stay with an A4. Since yours is running, I would guess fixing the issues with it make sense. You always have the alternative of rebuilding or installing a Moyer rebuilt engine. Trying to cobble something together from a used car or motorcycle engine makes no sense. A conversion to diesel is a BIG job and will cost much more than sticking with the A4. The A4 is a solid engine. Many have been running for 40 to 50 years.
 

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I would look long and hard at the costings here and whether you would ever want to sell the boat. It will sell faster and for more money with a diesel. You will never get all the money back but it is a factor.

Beta sell engines that drop right onto your existing A4 mounts. WARNING THERE ARE TWO DIFFERENT WIDTHS ON A4 MOUNTINGS. I assisted with a repower who bought the wrong engine. No biggie as the engine seller in Canada was happy to swap the kit over. It is a shame we were in Trinidad.

See http://www.betamarinecanada.com/pdf/A4_guidelines.pdf for more.

Cheapest route short term keep running the A4 doing the minimum. EXCEPT FIT ELECTRONIC IGNITION if it does not already have that upgrade.
 

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yeap!

fit a nice electronic ignition and it will be much easier to maintain still

of it runs still its a no brainer...
 

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Discussion Starter · #14 ·
Thanks,

You're right about having some stretch in the budget. I'm sure that even if the A4 is in a condition to be re-installed that we will want to address some other things "while we're at it" - not to mention the things that will be pointed out to us by the mechanic and the more seasoned sailors at the docks.
 

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Sticking with the A4 sounds like a good plan in your case. I needed to put a bit of work into mine when I bought it, luckily a carb rebuild got it going. I also added the electronic ignition just because I hate to adjust the points. If you do not do the work yourself and want to eliminate one service cost then the electronic ignition is very cost effective. I also went for an electric fuel pump and replaced the hot section and exhaust. Pretty easy things to do yourself, the A4 is pretty simple for sure. I bought the parts at Moyer Marine since they have a good reputation and have been pleased with the service. If you do swap the ignition you will also need a new coil pack (don't ask how I found out).

The fuel tank on my '72 was also not good, so if you drop all of that money into the motor you want to make sure it gets good fuel.

Best of luck!
 

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Drop by the Moyer Marine Forum. Great bunch of guys. Straight shooters even though they (we) love our A4s. Many have extra blocks, total spare engines, etc. Take some pictures, get some measurements and ask away before you make a decision.

Skywalker
1966 Tartan 27
Original A4 purring along
 

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Discussion Starter · #19 ·
Thanks everyone for the input. I am amazed at the kind consideration and helpfulness demonstrated by the members of this community as we were with the people at the docks when we became boat owners.
 

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What about repowering with an electric engine instead?
A friend of mine has been looking at this option for his 27 O'Day for a little over a year now. The problem is a real turn key electric is about the same all-in cost as a turn key diesel, but it then limits your range and ability to motor into steep seas or strong currents.

There are options that require you to do more of the engineering and are significantly less expensive but much more hands on.

He's opted to go the electric route after a lot of research but he's not the typical owner. He's an engineer who's already been through swapping in a used diesel to replace an Atomic 4 and only has a short distance to motor out to the bay. Honestly I think he's more interested from a tinkering standpoint, not that he really thinks it's the best option.

BTW his used diesel turned out to have a LOT more hours on it than the seller indicated and has given him no end of trouble. So if going the used motor route caveat emptor.
 
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