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Old 10-14-2014, 07:49 AM   #41
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Both over the road and commercial boaters know the fuel penalty of a DD. It is not significant for a recreational slow boat though. There are valid reasons the 2 strokers fell by the wayside. Emissions, weight and fuel economy being the primary ones.

My experience with the DDs includes side by side operations with Cummins and Cat in heavy earth moving. Engines were routinely seeing +3000 hours per year and careful tracking of fuel and maintenance costs a must for the large fleets.

By the late 70s stationary pumps and gensets had pretty well switched to 4 strokers with very significant fuel savings the reason. By the late eighties emissions issues ended the DDs long and glorious run in most NA applications. That didn't stop them from being dropped into large yachts though as emissions were not relevant and the 2 strokers reliability and familiarity carried the day in low hour usage.

My favorites were the lower HP 8V 71s. During the eighties we were able to get NAPA to rebuild them for about 2/3 the cost as compared to the DD guys and offer an equal warranty. But in those applications though we got rid of most of the DDs as down time for engine rebuilds was too expensive for the 24/7 applications.

Like one's favorite hunting dog, the DD mystique lives on, especially for the mechanics who don't have to buy fuel. Art DeFever was never a DD fan as he world cruised his designs and needed the 4 stroke fuel, size, and weight advantage.
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Old 10-14-2014, 08:51 AM   #42
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The difference between a perfect 16 Hp per gal and perhaps 20 Hp per gal is a huge difference for 24/7 high power use.

At 3gph for most boaters with only 200 hours a year , the difference is almost meaningless.

The difference in reliability , and service life easily pays for the 1/2 gph penalty.

For a modest trawler the 2-71 or 3-71 (60 or 90hp cruise)would be a realistic choice , even today , if the Air Police would allow it.

The WWII mine sweepers used aluminum blocks for their boats , that might help with the usual weight hassle . Talk about hens teeth!!!
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Old 10-14-2014, 09:00 AM   #43
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We have 4 of the 8v71's aboard the tug. 2 have 40,000 + hours with rebuilds around 20,000 hrs.
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Old 10-14-2014, 09:43 AM   #44
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The WWII mine sweepers used aluminum blocks for their boats , that might help with the usual weight hassle . Talk about hens teeth!!!
The two aluminum block 6-71s in my old boat were gensets in a WWII minesweeper. If I recall correctly, they were actually manufactured in the late-30's.

Weight aside, I prefer cast iron blocks. Since personally I'll never have twin engines on one of my boats again, that shouldn't be an issue.

BTW, it always freakin' amazed me that no matter how cold it was, that they would start within a a 1/2 second of hitting the starter. Zero problems in this regard!
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Old 10-14-2014, 02:03 PM   #45
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The issue at hand is which old engine to buy.

To answer that we might want to look ahead ten years to see which engine would require repower or just be repairable. My guess is the same discussion would happen then except the perkins parts would be harder to find while the detroits would still be leaking away with parts and mechanics everywhere..
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Old 10-14-2014, 02:38 PM   #46
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bayview,
I would buy the boat that had the engine in the best condition.
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Old 10-14-2014, 02:48 PM   #47
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Ordinarily I woukd agree but assuming both run ok at that age you need to consider what happens in the future. Tempis fugit and all that.
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Old 10-14-2014, 03:29 PM   #48
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It is all speculation on us TF ites as to the current condition of the boat and engine. Fact is though the Perkins factories are still around and owned by Caterpillar. No shortage of base engine parts but mani coolers have been an issue, go MESA! Water pumps are Jabsco and transmissions still made by ZF. Point me towards a DD factory.

As said earlier, let the best overall boat win. This Jimmy vs the world fight was lost decades ago. Even the Old Lehman came about as a Jimmy replacement, forty or so years ago!

Richard on Dauntless is sure happy he had a thrifty 4 cycle. If he'd a Jimmy his boat would have gasped several hundred miles short.


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Old 10-14-2014, 04:49 PM   #49
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I bleed CF2 40w oil, making me a Detroit, man, but I would not hesitate to buy a Perkins powered boat with engines in good condition. Like DD's and Mark Twain, reports of their demise are greatly exaggerated.
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Old 10-14-2014, 08:41 PM   #50
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In the end, the boat with Detroits was better laid out and better maintained. That and the fact that the broker for the DD boat started the engines for us without asking, and the diesel genset as well. When my wife asked the broker with the Perkins boat to start the engines, he said we would have to make an offer first. In my head I said to myself "I would never make an offer on a boat without knowing if the thing will even start"
Our offer was accepted! Now for all the inspections. I'm not expecting any problems.
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Old 10-14-2014, 09:36 PM   #51
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That's great! Good luck on the surveys and then happy cruizin! (from a Detroit owner)
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Old 10-15-2014, 06:22 AM   #52
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Ah yes makobuilders,starting a DD is one of life's pleasures.
As a mechanic I love an engine that starts instantly.Not to mention the sound of a twostroke V8.
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Old 10-15-2014, 07:54 AM   #53
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stornoway7-

not just that… had manual oil pressure gauges… manual stop (fuel cutoff cable)… manual tachometers. The only thing electric was the starter motor (but easy enough to replace with a manual spring starter).

can you imagine anything more reliable on earth?
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Old 10-15-2014, 08:51 AM   #54
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can you imagine anything more reliable on earth?

Death and TAXES
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Old 10-15-2014, 10:58 AM   #55
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can you imagine anything more reliable on earth?

Death and TAXES
Ughhh, you had to go and ruin a perfectly good moment
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Old 10-16-2014, 12:52 PM   #56
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WELL with just a National Sales Tax , we could repeal the second plank of the Commy manifesto

(a graduated income tax) ,,,AKA the 16 amendment ,

and just pay whatever taxes you desire , depending on what you consume.

Just think how the price of everything would GO DOWN with no billion dollars a year just for compliance.

Death will be harder to escape , but with time ????
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Old 10-16-2014, 05:02 PM   #57
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Back to your area of perfection FF....boats....
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Old 05-31-2015, 07:30 PM   #58
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The noise may be the biggest downside of the DD. A good exhaust system and good engine room isolation/insulation can control the noise. But not all boats did a good job with this. It is hard to kill that exhaust drone on a DD.

Make absolutely sure you can live with the noise.

I did some work on a Hatteras LRC with 4-53n, it had mufflers but was still too loud for my tastes. Kind of like a Harley: The noise is fun. For five minutes.

My vote is for the Perkins. Much quieter, and a lower frequency tone. Love me some old Detroit iron, but I have paid with some hearing loss.
I have owned the 8V DD on a Canoe 37, the 6.453 on a fishboat, and had a Cummins 330 on Hercules. And a Saviem 210 on a 31 Enno. The latter slobbered, had a shrill turbo tone, and blew white smoke enough to raise a fire party on every starting.

The Cummins sounded like the trucks that pull up to you at stoplights, for some reason, and eventually I didn't want to hear it anymore. Gimme a Gardner to listen to.

The 6.454 "Green Leaker" didn't and howled like a 2-stroke. Hit above its weight and hummed. Dean at Saltspring straightened me out on soundproofing and for $400 worth of soundproofing I knocked it down low, where I operate. ;-)

The DD 8V's did leak, somewhere high onto the valley, but a gravity leak I mopped up. They too performed up to spec and beyond, and I could stand to listen to them. Absolutely the way to go given the WWW, especially, I feel. In Craigslist we trust.

And I agree, knowing their provenance helps. My DD's always professionally prepped each season.
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