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  #1  
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Repowering a Pearson 31

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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Re: Repowering a Pearson 31

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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Re: Repowering a Pearson 31

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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Re: Repowering a Pearson 31

Haha, Rich beat me to it.
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Re: Repowering a Pearson 31

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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Re: Repowering a Pearson 31

If you are willing to do some of the work yourself the atomic 4 is a great motor. Check out the forum at Moyer Marine Atomic 4 Engine Rebuilding and Parts for help. All old motors require tlc and new diesels require maintainance.
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Re: Repowering a Pearson 31

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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Re: Repowering a Pearson 31

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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Re: Repowering a Pearson 31

I will discuss the possibility of running the alternator as you suggest with our mechanic. Never thought of that. Thanks
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Re: Repowering a Pearson 31

Quote:
Originally Posted by RichH View Post
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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