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Old 04-25-2021, 10:58 PM   #21
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Havingnthe Walkers will certainly make it much easier to keep the engine room cleaner. They should run forever if you stay out of the throttles.
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Old 04-26-2021, 07:19 AM   #22
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Originally Posted by Capt. Kirk View Post
I have received conflicting feedback on how to best run the 6V92s.

Some people have said, “you can’t baby these girls, you got to run them on the pins.” I take it that means at higher RPMs.
This is not my inclination.
Others here have said:
“That engine, when run hard, did not last very long. Piston rings and liners might get 1500-2500hrs.
BUUUT.. That very same engine if run at hull speed and like 1000-1200rpm could last many thousands of hours. So even if rated for 550hp, if you run it at say 100hp, it will last, without doing anything but keeping out of the throttles.”
“At modest low output the DD are almost a forever engine.”
I plan to cruise the boat at low RPM at 8 or 9 knots which I expect qualifies as, “modest low output.” Running her this way, I assume I will need to run up her RPMs to blow out the carbon at the end of a long day.
The owner says he ran the boat, “at 8 to 10 knots, occasionally 20 knots.”

Please let me know if you agree with that these engines should last a long, long time if run modestly.

Some of the older, low output DDs did like to be run towards the upper end of their RPM range, particularly in trucks where high RPM didn't necessarily mean full load. The higher output ones shouldn't be run like that. If run reasonably, they'll live a decent life. But if run flat out or close to it, they'll burn up just as fast as a pair of gassers being run like that.
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Old 04-30-2021, 02:50 PM   #23
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Just keep them between 1200 and 1400 rpm , they will last forever. I like the 71's better, also prefer the mechanical injectors over the DDEC electronics. Just keep good oil and new antifreeze/ anticorrosion fluids in the block. If you have intercoolers (especially sea water cooled intercools) disassemble and renew the gaskets ever 5 years as a preventive maintenance program.
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Old 04-30-2021, 02:52 PM   #24
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If they're in good condition now you should be able to keep them running for longer than it will be possible to keep you running. 1000 - 1200 rpm a little low IMO, go to 13-1400, combustion pressures high enough to seal the rings, avoid running much below 60% power, that will mean pushing it a little beyond hull speed. I think blowing out the carbon is snake oil, and a routine of it combined with chronic low power running should cause increased deposits in ring grooves increasing the risk of ring breakage. These engines were designed to spend most of their life producing 80% of rated power.
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Old 04-30-2021, 06:41 PM   #25
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Different boat, different motors, but my friend with a 53 Hatteras DD 8V53s says the same - run it at 8-10 knots most of the time, run it at 15 knots every once in a while.
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Old 05-01-2021, 09:08 AM   #26
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We have had boats with 6-71N, 6-71TI, 6V-92TA and 8V-92TA Detroit’s.

The 550hp 6V-92TA was in a 38, Blackfin SF. They made it to 3600 hours before rebuild in place. Running a MY can be similar to a SF in that you spend long hours at trolling speeds and then a few hours at higher cruise.

Here is how to get longer life out of your 6V-92TA:

Make sure that at full load, with all gear on board, full fuel and water, no waste, that your WOT rpms are 2350. This is imperative to have the propellers correctly loaded. Re-Prop if necessary to get this right.

Never cruise for extended times over 1950 rpm. Never.

Install pyrometers and run them correctly. You will find the Exhaust Gas Temp specs in your manuals, they will be in a range, do not run it past that range and generally keep them in the middle.

If your are running all day at 8 - 12 knots you should blow them out by running up to 1850 - 1950 rpm for 15 or 30 minutes before entering the harbor.

You have to find the right spot for low cruise, you do not want to be on the edge of where the Turbo kicks on and off. Avoid that range at all costs, cruise below it or above it but never on that spot. It varies on sea state and load, pyrometers will help you here.

Perform oil changes religiously, never more than 200 hours apart.

Get the best fuel filter system in place you can but. Multi-stage 5 microns before the engine.

Spare hoses and fittings onboard, plus always carry 5 gallons of diesel in a jug. Necessary for priming filters if you go through a bad batch of fuel and clog the system.

Walker or Racor Airseps are mandatory.

Happy boating!
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Old 05-01-2021, 02:19 PM   #27
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1994 DD 6v92TA

I don't notice the engine noise while motoring. It's just a part of boating. We've had our boat 7 years and have had no major issues. And our engine room stays clean with just a few pads under the engines.
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Old 05-05-2021, 04:23 PM   #28
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If you can put up with the noise, and don't mind a few oil drips, buy the boat.

There are a lot of wives tales on how to run them. Some say on the pins to keep them hot and clean, others say under 1200 rpm and they last forever.

We have 8v-92 TA's in ours. I let them warm up at the dock, then head out for the day/week. Its a 1978, but the engines have been rebuilt and now have 500 or so hours on them.

I don't run it on the pins, I don't chug it along. Mostly at 10-16knots
Change the Oil, and change the fuel filters. I do oil changes at 100 hours, and all fuel filters. DD run a lot of fuel through the system, and return a lot of it back to the tanks, its like a built in fuel polishing pump!

Carry extra oil, as they use oil.
Carry extra fuel in a jug as mentioned above.
DD hold a lot of oil, I pack 7 extra gallons and a filter set, this is enough for one engine. I also pack a full set of extra Fuel filters for the boat.

Pack an extra sea impeller, and the proper tool's to change one out.
Carry the right oil, DD like straight 40 weight low ash.
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Old 05-05-2021, 04:43 PM   #29
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You are not crazy but you need to move cautiously regarding those rebuilds.

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Old 05-06-2021, 01:15 PM   #30
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Had a 48 Hatt with 6/92TA, ran at 1400 rpm which gave me 10kts. Ran them up before shutdown, had walker air seps and resealed a few spots and no no oil leaks or messy bilge. 3000 hrs in 12 years. Loved my DD’s
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