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Discussion Starter #1
I am considering trying to put a perkins 4-108 in my C30. I have no problem modifying the engine compartment, but is this a reasonable thing to do?
I haven't laid eyes on this motor yet but I read that people replace them with a yanmar 4JH or somehting like that, because the yanmar is half the saize with the same power. Does any one know the power or dimensions of the perkins.
I think I would prefer to use my boat more like a trawler anyway. But I need to know if this is a feasible project.
 

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The old Atomic Four and it’s replacement diesel (from Universal/Westerbeke) will push a C30 along at hull speed. Any more horsepower will just burn up fuel with no real improvement in performance. I’m guessing that the Perkins will have half the fuel economy. The other thing to consider is there is a specification of square feet of airspace per HP needed in the engine compartment for proper cooling and aspiration. Doubling the engine size without increasing the compartment will lead to problems. You could get by with running your blower all the time and putting in an oil cooler, but why? You won’t be increasing performance, just making the cabin that much noisier and hotter when running the engine.
 

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No. A 4-108 is a great, easily serviced and common diesel, but it's neither light on a horsepower per pound basis nor is it particularly economical. It is best used where you anticipate motoring at a constant, not particularly high RPM (say 2,200 or less) for hours and hours, inferring a fuel supply to feed that. The smallest boat I've seen one in was a 36 foot full keeler, and I've seen most in 40 footers.

You are far better off with a 20HP or less diesel or a rebuilt Atomic 4. If you can acquire a running Perkins for peanuts, I have no doubt that you can trade it as is for a newer, lighter, and more appropriately powered engine for your needs.

From what I recall of the C30 engine space, if you could even jam a 4-108 in there, you'd need half-inch thick fingers to service it, and it would melt the glass with its fiery warmth.
 

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The old Atomic Four and it’s replacement diesel (from Universal/Westerbeke) will push a C30 along at hull speed. Any more horsepower will just burn up fuel with no real improvement in performance. I’m guessing that the Perkins will have half the fuel economy. The other thing to consider is there is a specification of square feet of airspace per HP needed in the engine compartment for proper cooling and aspiration. Doubling the engine size without increasing the compartment will lead to problems. You could get by with running your blower all the time and putting in an oil cooler, but why? You won’t be increasing performance, just making the cabin that much noisier and hotter when running the engine.
 

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SaltwaterSuzi/CapnLarry
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Perkins 4-108 - (Dieselbub)

Our '77 Morgan Out Island came with a Perkins 4-108. I hated it. It spewed oil like geysers. It rattled and vibrated and shook and required more maintenance than I was willing or able to offer it.

(One gentleman told me, in reference to the Perkins: "You know why the English don't make computers?" "No, why?" I asked. "Because they haven't figured out how to make them spew oil.")

It was rated at (if I remember) 50 HP at 4000 RPM. No Perkins 4-108 ever ran at 4000 RPM. At 2000 it wanted to climb up into the cockpit with us so we ran it at about 1800 max. At that speed it was rated at about 37 HP. It had a slushomatic transmission which sopped up about 10 hp so we had 27 horses coming out the back. Not much for a 28,000 boat.

After about 8 years of percolating the Perkins, it finally seized up. We pulled it out and had a ceremony, where I shot it, called it names (including Dieselbub), and threw things at it. It responded by squirting oil at me one last time. Oh, how I hated that engine.

We replaced it with a smaller, quieter more powerful Westerbeke 55B. We're now out shopping for waterskiis.:rolleyes:
 

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I sail on a C&C 35 with a 2 cylinder 13.5 HP BETA that pushes the boat at 6.8 knots and was pushing us at 5 knots into 30 knots true wind with a nasty 6 to 8' sea

The correct prop is the key as its a 3600 RPM motor and we have never run it above 3200 RPM
 

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I've had my 4-108 to 3900 RPM a few times. It buries, and I mean buries the stern on Oh Joy at 7.5 knots or did before it expired. I'm looking for a smaller engine m'self. Oh Joy is slender and only displaces 15,000 so I don't need that noisy, oil slinging monstrosity.
 

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Discussion Starter #10
"It responded by squirting oil at me one last time." quote by Larry
You had me rolling with that story.
tommays-that sounds remarkable for a 13.5 hp engine on a 35' boat.
After all the feedback, I think the perkins is just too big. I am going to look at a 2QM15 tomorrow. If I was gauranteed that it would push my boat at 6.8 knots I would have no doubts about buying it. But I will be replacing a ysm12 and not sure if 3 more hp will be enough to satify my need for speed.
 

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We pulled it out and had a ceremony, where I shot it, called it names (including Dieselbub), and threw things at it. It responded by squirting oil at me one last time. Oh, how I hated that engine.
Dieselbub. Classic. Your pain, maybe, but my laughter as that was a very funny post.
 

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HS: The need to push your boat at 6.8 knots (which is at or slightly above the hull speed of a C30, I would think, as my 33 footer is 6.9 knots, above which I'm "surfing" or in a current) is vanishingly rare. The fastest I've regularly gone in my 33 footer is 5.8 knots, because that last knot, while possible, was obtained at great cost in fuel consumption, noise, heat and vibration.

It isn't worth it.

Sailboats sail. Prop whatever engine on the basis of its power curve and your desired stopping power and backing down thrust. Sailboats usually only ever go "loud and proud" trying to back down, stop or while making a sudden move (sarcasm intended) while docking. My engine is best left idling in neutral if I can glide into dock without using reverse. I really don't need it to push the boat at hull speed, if only because motoring a sailboat that fast is gravely missing the point of owning a sailboat at all.
 

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LarryandSusan, your story made my day! :laugher
 
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