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Old 12-16-2020, 09:36 AM   #81
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If I set the idle on my 12-71’s too low they will chirp the low oil pressure alarm and occasionally stall if shifting into gear against the boats movement. 36x36 inch props have a lot of resistance, especially when pushing against the boats momentum.

And nothing sounds as good as an idling Detroit V-12! I will admit to being ignorant of the sound of a V-16 though.
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Old 12-16-2020, 10:24 AM   #82
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In Vietnam I ran PBRs with twin 6v53s in a special ops configuration. The engineroom was well insulated, about 1 foot of foam, and the exhaust, after being muffled, was released underwater. At idle, you could only hear the splash noise of the water jets. And at full throttle you could only hear them 25' into the jungle. We normally cruised just short of flat out. DDs don't have to be noisy.
Thank you very much Lepke.
I’ve always thought so.
Noise is noise and a “foot of foam” sounds like they took the job seriously. That’s the problem w yachts. They just don’t take the job seriously. They are big shots and who will tell them it’s too noisy?
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Old 12-16-2020, 11:10 AM   #83
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One reason for smooth long life is 7 main bearings on 6-71 .


Most will idle at 350 - 400rpm and still not shake.
Exactly!
Here's a good video By BGM...much more robust, more than twice bearing surface than their cousin V configuration series.
My 671s are set @500 & do not use the buffer screw to adjust idle RPM


https://youtu.be/hWfgUOK2xwQ
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Old 12-16-2020, 11:14 AM   #84
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Thank you very much Lepke.
I’ve always thought so.
Noise is noise and a “foot of foam” sounds like they took the job seriously. That’s the problem w yachts. They just don’t take the job seriously. They are big shots and who will tell them it’s too noisy?
That is a bulletproof Uniflite 31 hull MK1 or MK2 with twin DD with Jacuzzi jet.
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Old 12-16-2020, 11:31 AM   #85
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Charlie still don't surf....
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Old 12-16-2020, 12:07 PM   #86
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Charlie still don't surf....
Maybe not then, but he does now! He also owns the bungalow resort and bar/restaurant on the shore too. A lot has changed since Charlie won the war......
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Old 12-16-2020, 12:44 PM   #87
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That is a bulletproof Uniflite 31 hull MK1 or MK2 with twin DD with Jacuzzi jet.
I was working at Uniflyte in the early 70’s when these guys were being made. Don’t remember the bullet prof feature but it was probably there ... I just don’t remember it.

When I worked at Washington Iron Works in South Seattle I had the pleasure of frequently hearing DD engines start up. But when they reved them up do some work it was definitely noisy. WIW was a very large manufacturing facility not unlike a WWII train depot. Lots of train tracks inside but I don’t remember them being used. I don’t remember them using any other engine in the logging equipment they typically manufactured.
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Old 12-16-2020, 01:42 PM   #88
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I was working at Uniflyte in the early 70’s when these guys were being made. Don’t remember the bullet prof feature but it was probably there ... I just don’t remember it.

When I worked at Washington Iron Works in South Seattle I had the pleasure of frequently hearing DD engines start up. But when they reved them up do some work it was definitely noisy. WIW was a very large manufacturing facility not unlike a WWII train depot. Lots of train tracks inside but I don’t remember them being used. I don’t remember them using any other engine in the logging equipment they typically manufactured.
Very cool!
by the 1980s Uniflite had turned into the country’s biggest production boat builders.
Company like Grand Banks are now copying Uniflite's lines after 50 yrs later.
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Old 12-17-2020, 05:39 AM   #89
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"If I set the idle on my 12-71’s too low they will chirp the low oil pressure alarm."

On GM coaches the air cond requires about 60-80hp

.GM coaches were monocoque , light weight aircraft style construction. The compressor has to be engaged at very low speed to keep it from ripping apart the mounts. A slow, slow idle was required.

GM used the low oil pressure light as part of the safety system to allow the system to engage the compressor.

With the low oil pressure light on a 9 inch chevy truck clutch was released to take the load.

Low oil pressure at idle is normal for many DD .
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Old 12-17-2020, 07:53 AM   #90
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"If I set the idle on my 12-71’s too low they will chirp the low oil pressure alarm."

On GM coaches the air cond requires about 60-80hp

.GM coaches were monocoque , light weight aircraft style construction. The compressor has to be engaged at very low speed to keep it from ripping apart the mounts. A slow, slow idle was required.

GM used the low oil pressure light as part of the safety system to allow the system to engage the compressor.

With the low oil pressure light on a 9 inch chevy truck clutch was released to take the load.

Low oil pressure at idle is normal for many DD .
This is true. "Low oil pressure "is kind of an oxymoron in a DD. One of my old tour busses had ,maybe, on a very cold day,about 18 lbs of oil pressure at startup. Then,at operating temperature, 5-7 lbs. And we ran the tires off of it. But,as long as a DD has any oil pressure, it's good to go.
When I first went to look at my GB, I was told it would either have FLs,or Cats. I would have been happy with either. But,when I opened the floor up and saw those 2 DDs,I was halfway glad,and the other half disappointed. Glad it was DDs in there, because I've had nothing but good service from the 5 other DDs I've had but not so glad because of the volume in the salon being a little more than expected.
That being said, I am happy to take a little extra noise to have those bullet proof babies beneath my floors. Keep clean oil in those babies,and they will outlive me and my children. For me,the simplicity of them make it easy for anyone to be able to learn the basics of how to do their own service work. (Except for the "Armchair Admirals "). Anyone willing to get their hands dirty can take care of their own motors.
And,could y'all please talk a little louder? My hearing ain't as good as it used to be. Lol
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Old 12-17-2020, 08:23 AM   #91
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Nothing wrong with low oil pressure at hot idle on a DD. It freaks a lot of people out, especially those used to gassers.

Remember that the con rods are drilled to carry oil to the piston cooling nozzles on the tip of the rod. Constantly spraying the underside of the piston (on trunk pistons). On two piece cross-head pistons (turbo versions) the piston has a semi-closed volume fed by the rod that fills the chamber and "shakes it" to cool the crown.

There is a lot of oil diverted to cooling the pistons, and that means low pressure at idle.

Some seem to have bigger pumps, probably just to get customers to quit complaining about it.

If I see hot idle oil pressure at 500rpm at 5-10psi, I don't even blink. Should be 35-40 at hot cruise rpm of 1500-1800.

Nothing wrong with a "chirp" from oil press alarm when shifting. At least you know the alarm is working!!

And DD's run oil HOT. Folks wonder why I wear jeans doing a summer DD test run. Rub a bare leg against a 230F oil filter and you are getting blisters!!

You can idle these things down to usually 500rpm with a good governor and careful setting of the governor/buffer screw. But with some combos of big prop and certain gears (that shift quick), if set too low will stall. I set them so at hot idle I can go from fwd straight to rev and if it stalls, set it up a bit higher. In a maneuver, when operator needs to go straight from fwd to rev it usually is a situation where you don't want a stall!!

Old Allison hydraulic gears were great on not stalling. Nice slow clutch engagement gave the engine a chance to recover. But one complain about that, too.
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Old 12-18-2020, 03:46 PM   #92
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Originally Posted by Nomad Willy View Post
I was working at Uniflyte in the early 70’s when these guys were being made. Don’t remember the bullet prof feature but it was probably there ... I just don’t remember it.

When I worked at Washington Iron Works in South Seattle

Uniflight's PBRs weren't bullet proof. Most rounds went all the way thru the hull unless they hit an engine.
I use to run a Washington Diesel in a salmon packer, rigged for tuna. 6 gallons an hour @ 9 knots, in an 85'x18'x9' hull, maybe 150 tons. Wa Diesels were made by Washington Iron Works until the cheap war surplus engines drove away the business. The engine was a forerunner and similar to DDs mechanical injector, except all the injectors, rockers, and linkage was exposed and had to be oiled manually. The engine looked a little like an Atlas, but much heavier built. Atlas died about the same time, too.
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Old 12-18-2020, 04:07 PM   #93
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Lepke, Did you do your training on Mayer Island? Used to see those Bad Little Boats doing exercises in the bay decades ago.
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Old 12-18-2020, 08:25 PM   #94
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Lepke, Did you do your training on Mayer Island? Used to see those Bad Little Boats doing exercises in the bay decades ago.
There was a shooting range in San Pablo Bay where the .50 cal had enough room to shoot without killing some homeowner. Otherwise we trained north of Grizzly Bay in Montezuma and Suisun sloughs. There we had adapters for shooting blanks and a number of training simulators for grenades, mortars, and artillery. There was a Quonset Hut base camp and a "friendly village" that housed our enemy. At night we defended the base perimeter and days did patrol and boat searches. It was common to see the boats going between the training areas.

I suppose it was a decent exposure to the job, caring for the boats and weapons, but it didn't relate well to what I experienced.
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