Low oil Pressure Detroits

[retriever48]

I have a 48 Ocean with 6-71 485hp DD located in Baltimore. My starboard motor is running abot 35 psi oil pressure conpared to 40psi on the port engine. After running on plane and backing down to idle, the starboard engines low oil pressure alarm goes off and it is just below 10 psi. Looks like the port is around 11psi. Is there any recommendations on oil to use to help out with the oil pressure. Right now I'm using DD 40w oil I buy from J & T. The rpm is about 700. I'd actually like to lower the rmp if possible to help slow the boat down at idle. Its going 6.5 mph at idle. I need to get it slowed down for trolling for rockfish. Any recommendations would be great. thanks.

[38Blackfin]

Originally Posted by retriever48

I have a 48 Ocean with 6-71 485hp DD located in Baltimore. My starboard motor is running abot 35 psi oil pressure conpared to 40psi on the port engine. After running on plane and backing down to idle, the starboard engines low oil pressure alarm goes off and it is just below 10 psi. Looks like the port is around 11psi. Is there any recommendations on oil to use to help out with the oil pressure. Right now I'm using DD 40w oil I buy from J & T. The rpm is about 700. I'd actually like to lower the rmp if possible to help slow the boat down at idle. Its going 6.5 mph at idle. I need to get it slowed down for trolling for rockfish. Any recommendations would be great. thanks.

There are a couple of DD guys here. If one of them doesn't jump in soon, go to www.boatdiesel.com, main diesel forum, 'engines' dropdown, or use the search. Go back several years.

good luck!

Randy

[Dunk]

Originally Posted by retriever48

I have a 48 Ocean with 6-71 485hp DD located in Baltimore. My starboard motor is running abot 35 psi oil pressure conpared to 40psi on the port engine. After running on plane and backing down to idle, the starboard engines low oil pressure alarm goes off and it is just below 10 psi. Looks like the port is around 11psi. Is there any recommendations on oil to use to help out with the oil pressure. Right now I'm using DD 40w oil I buy from J & T. The rpm is about 700. I'd actually like to lower the rmp if possible to help slow the boat down at idle. Its going 6.5 mph at idle. I need to get it slowed down for trolling for rockfish. Any recommendations would be great. thanks.

What is J & T saying about the oil pressure??

I ran headboats in the Keys that had WWII Tank 6-71's in them. No alarms anywhere and they'd drop to 2-3psi on the guages after they were hot and you chopped the throttles. 25-30psi is the best I remember on them, but they were naturals and only put out 137hp, had 15,000hrs++ on them. Several half ass rebuilds, but they kept running. One pair was pushing a headboat 70ft long and 27ft wide.. 6-7kts@1100rpms to the reef and back everyday.. Anyone remember the Capt Winner out of Holiday Isle??

What bothers me the most is you are already running 40wt oil. Sometimes oil that heavy can starve the back end of the value train. I had that problem with my Volvo TMID 9.6 which was a bigger 6 cylinder inline similar to the 6-71. I used to get valve tap with 40wt, but she was quite with 30wt. I used to mix the two for about 35wt oil. I only used Chevron Delo..

[54bullwinkle]

Had same motors. 40w is rec oil for those motors. Do not use lighter oil.
I had same problems with one of mine as well. After she ran, when I would shift while docking the oil pressure alarm ( I hated that bell ) would sound. I changed out the oil pressure senders and she was fine.

You can get the senders at a truck parts supply. You can still get filters and other parts from road engine suppliers.

There is an adjustable threaded rod on top that controls the rack. This will adjust your idle. Mine needed to idle a little over 600 or they would roll.

[CB Haws]

Hot at idle 671's don't make much oil pressure 2-5 at best; and it is not a problem. Change the alarm switch.

[caltexflanc]

I can recommend a terrific DD mechanic in Baltimore. Call Tom Hug of MR Power Specialists at 410 574 1625 or cell# 410 274 7636. He has great communication and teaching skills as well as deep knowledge of these engines. He did the surveys on my 8-92's and some subsequent work, and is very honest about what you need to have done and what you could, but don't have to have done.

George
Hatteras 56MY

[CapnDean]

Change the oil pressure switch. The only worse sound than that bell at cutback, is that bell at 2/3 throttle. Also....how are you turning on your warning circuit? A toggle switch? Key Switch? Or a fuel pressure switch? I ask because you might up the psi on a fuel switch and solve it that way. My last 671 did not have an ignition switch..it was manual shutdown. I had a 5 lb 'make' which energized the alarm system only when it had 5 lbs of fuel pressure. When fuel pressure dropped below 5 lbs, it killed the power to the alarm. Hence the alarm did not sound continously while the motor was off. If you upped that to say 15 lbs...ya think that would silence the bell?

[retriever48]

The switch is a toggle on the bridge right next to the start button and the kill button. I'm new to this boat and DD's. The alarm only came on when I got the rpm under 750. Like I said, I'm trying to slow it down just a bit. So, during the survey/sea trial it didn't com on at warm idle. I have a shop manual on the way so I can learn about these beasts!! Any leads on truck part suppliers if I decide to switch the pressure switch out? J&T is right up the road from the boat, so I'll be talking with them. I'm sure the price is inflated with them however. Thanks for the info guys.

[CapnDean]

Whoa Nellie: Your alarm switch is on a toggle....think about it. Are you going to always remember to toggle that bugger on? You may consider putting it on a fuel pressure switch. I always worried that I would silence that bell and forget to turn the alarm circuit back on....

[retriever48]

The switch actually activates the entire gauge cluster per engine. Not only the alarms, but the actual gauges themselves. Standard starting procedure is to turn on the switch then fire the engine off. So it's kind hard to forget to turn it on unless you never look at the gauges. I'm always looking at my gauges!!