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Old 01-24-2016, 02:51 PM   #21
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Why not Bill?
Because the point of pre-lubing is to have oil AND oil under pressure flowing before the engine ever turns over.

It's always been my understanding that oil under pressure is being forced in between the bearing and what ever is "riding" on it. So that the two surfaces never really come into contact with each other.

That is why the claim is made that most of the wear happens at start up when there is no oil under pressure being injected between the two surfaces. So the surfaces are in contact, or perhaps more in contact than normal, with each other till the pressure builds.

At least that is the theory as I've seen it presented in the past.

I don't know about you guys but in most cases when I've been rolling over an engine that is not starting up right away, I can tell when the oil pressure has built up by how much easier it starts to turn over after the pressure comes up.

That said, I'm not telling the OP to run out and set his oil change pump up as a pre-oiler.

For a long running fairly bulletproof engine like a Lehman, they probably would be of little or no benefit.
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Old 01-25-2016, 06:35 AM   #22
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The accusump that I mentioned in post 5 is a good way to go if you feel that a prelube would help prolong your engine.

High pressure is relative but 60-80 PSI of cold oil would require a bit more then a rubber impeller pump. Some engines have even higher oil pressure when running, pre-lube requires a bit more then the "limbering up" of cranking for a few seconds without starting.

You want real oil pressure for a bit, how high does your oil pressure gauge read when cranking?

Bill in the above post you make a good argument as to why you really want a high pressure pump as a preoiler.

I agree this is not really going to do much most of us, I you had an emergency response engine that was going to be started cold and ran hard right at startup perhaps it might make somewhat of a difference. You just don't see many run-out FL120
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Old 01-25-2016, 09:28 AM   #23
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IIRC oil routing is not simpe. Cranks have passages that pick up oil as it turns not simply flowing around between the bearing and crank. cam followers are a dry start concern and each engine probably lubes those differently. Cold heavy oil isn't likely to flow through narrow clearances very well. Cylenders are not lubed by pressure. All in all I think the effort not worth it. Some engine makers give dry start procedures to be used after long storage. Blocking air intake should decrease compression loads and make fuel off spinning easier and with less bearing load.


AL that being said I can only remember one engine failing from bearings and that was after the owner ignored low oil pressure on a many thousand hour engine and made the trip to Venezuela from FL and used the boat there for several years. Spun bearings are not unheard of after a rebuild but general failure is rare.


Brings to mind an answer to some questions from old diesel commercial operators.


How do you store the engines Capt? "turn them off"
How do you start up your stored engines Capt? "start them up"
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Old 01-25-2016, 09:54 AM   #24
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IMO only we boaters obsess over our engines. Diesels are used in equipment round the world where thy are just shut down and started up after any period of storage.


I wonder if any ex military guys know what Govt procedures are?
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Old 01-25-2016, 03:54 PM   #25
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I wonder if any ex military guys know what Govt procedures are?

Jump in, hit the starter, put in gear and drive it like ya just stole it.

Ex-USAF Firefighter back in the SAC days

All we knew about pre-lube, it called foreplay as I recall
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Old 01-25-2016, 06:01 PM   #26
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I think an oil pan heater that kept the oil in the sump around 120F would be simpler and more beneficial reducing wear. Especially if the engine is used at least monthly. Read www. "bobstheoilguy.com".
In the nuclear power industry, we had both pre-lube pumps and oil heaters to keep straight 40 weight oil >110F. Both were a constant source of maintenance headaches. The reason was the requirement to start the engine from 0 to rated rpm in <10 seconds and accept full load (4443 Kw) in <130 seconds without damage. Try that with a cold diesel!
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Old 01-25-2016, 07:43 PM   #27
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I think an oil pan heater that kept the oil in the sump around 120F would be simpler and more beneficial reducing wear. Especially if the engine is used at least monthly. Read www. "bobstheoilguy.com".
In the nuclear power industry, we had both pre-lube pumps and oil heaters to keep straight 40 weight oil >110F. Both were a constant source of maintenance headaches. The reason was the requirement to start the engine from 0 to rated rpm in <10 seconds and accept full load (4443 Kw) in <130 seconds without damage. Try that with a cold diesel!
...I think that is all the USCG does....at least into the 90's with the older boats.

Haven't heard anyone discuss pre-lubers but my circle of info has all but withered for everything but SAR.
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Old 01-25-2016, 08:15 PM   #28
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Large industrial and marine engines have coolant heating and prelube pumps. Coolant heating to control corrosion and keep oil viscosity down. Prelube probably traditional, but lube circuit might take a LOT of time to fill compared to our little engines.

I like the idea of prelube, but not enough to put on my own engines.
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Old 01-25-2016, 11:17 PM   #29
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system using a Reverso pump

This is the one I purchased - not installed yet, so I don't know how well it works. There is a link to an installation drawing. The pumps are from Reverso. Either connect the oil pressure switch and have the back-up function or just install the on/off switch and use it as pre-oiler only:

Pre-Oiler and Back-Up Engine Oil Pump | INFINITY Aerospace
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Old 01-25-2016, 11:25 PM   #30
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I recall 110-115 revolutions on a hand driven gear pump to prelube a Fairbanks Morse ND81/8 prior to snorkeling. Have lift pumps on some giant AC motors (>20,000 Hp) and refiners with journal bearings at a mill I worked in. No need to have on my truck or boat. One of those things that are a great idea, but probably less so in actual practice.
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Old 01-26-2016, 06:56 AM   #31
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I like prelubing engines that have sat for years, but not the ones that have sat for a few months.
Interesting. I've disconnected the electrical solenoid connection on my Cummins and cranked the engine over for 15 sec if I haven't used the boat in a month or so and when bringing it out of winter storage. Perhaps I'm just wearing out the starter.
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Old 01-26-2016, 09:15 AM   #32
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To perhaps help lubrication using a in coolant pre- heater ,to warm the entire engine for 12 hours or more would probably help lessen the wear as the engine warms up and gets back to operating shape.

Many other uses (like cold weather starts) and no danger in the install , or operation.
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Old 01-26-2016, 09:18 AM   #33
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I recall 110-115 revolutions on a hand driven gear pump to prelube a Fairbanks Morse ND81/8 prior to snorkeling. Have lift pumps on some giant AC motors (>20,000 Hp) and refiners with journal bearings at a mill I worked in. No need to have on my truck or boat. One of those things that are a great idea, but probably less so in actual practice.
I've seen the same in industrial experience. In two cases very large diesel generating stations had warm oil circulation systems running 24/7 on standby engines. No engine was allowed to be off for more than a week or so before it was fired up.

On large grinding mills weighing many hundreds of tons an oil jacking system is used to lift the rotating piece off the stationary bearing.

But as already said, not so important on our little diesels, even after a winter's layup.
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Old 01-26-2016, 10:25 AM   #34
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On some engines, the oil pump is above the oil level a good bit- Cummins, some Detroits, some others.. And grinding away at the starter may spin the pump so slowly that it does not pick up a prime. Those pumps will not pump air very low rpm, and they need to pump air to draw in the oil.

I've been called out where someone was cranking while holding stop and waiting for oil pressure to rise. crank, crank, crank, crank. Pressure never comes up. I come and check things out and simply start the engine. Pressure comes up in five sec.

I don't think cranking while holding stop is a great idea, unless on your particular engine the pressure comes right up. Bearings are wet with oil even without pressure, and it takes relative velocity of the surfaces to create the oil film. 15sec of slow rpm on starter could be worse than five seconds of engine running. Pumps prime faster when you spin them faster.
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Old 01-26-2016, 10:52 AM   #35
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Thanks Ski for that info. I can't count the many times I've done something sometimes at great expense and time only to find out later I was doing more harm than good.

My 4.3L Mercruiser runabout with a Webber carb must be started by cranking with the stop switch pushed off. The Webber carb drains fuel when not used within a week so no fuel to start. As a safety device the fuel pump will not pump w/o oil pressure. So by cranking the engine with the stop switch off, the engine builds oil pressure and allows the fuel pump to resupply fuel to the carb. About 15 sec is all it takes. After that the engine starts normally.
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Old 01-26-2016, 11:38 AM   #36
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Thanks Ski for that info. I can't count the many times I've done something sometimes at great expense and time only to find out later I was doing more harm than good.

My 4.3L Mercruiser runabout with a Webber carb must be started by cranking with the stop switch pushed off. The Webber carb drains fuel when not used within a week so no fuel to start. As a safety device the fuel pump will not pump w/o oil pressure. So by cranking the engine with the stop switch off, the engine builds oil pressure and allows the fuel pump to resupply fuel to the carb. About 15 sec is all it takes. After that the engine starts normally.
Tim you could wire a pushbutton switch to a positive feed to your fuel pump and give it a 10 second carb fill before each start so you don't have to crank.

The Assistance boat developed an electrical issue at the height of the season. It prevented the fuel pump from running at all...I ran the boat for 5 more months with just a jumper wire over to the "hot terminal" on the starter. Not the best, just made sure the batt switch was off when the engine wasn't running. Not hard to notice the noisy fuel pump anyhow with the engine off.

The benefit of this (which I don't recommend as a solution) was by bypassing the oil cutoff was much better starts than ever by having the fuel line already pressurized. Many of the new fuel pumps are the on demand type anyhow so overfilling the carb isn't likely...but still a concern...thus my suggestion of a momentary switch.
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Old 01-26-2016, 12:11 PM   #37
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Tim you could wire a pushbutton switch to a positive feed to your fuel pump and give it a 10 second carb fill before each start so you don't have to crank.
Yes thought of that but just to lazy to hook it up. Cranking procedure only necessary if the boat hasn't run for a week or so.
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Old 01-26-2016, 10:52 PM   #38
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I remember back years ago reading about a starter with a lube pump built on the end of it. When you energized the starter it would spin the pump but the pinion wouldn't engage the flywheel until the engine oil pressure was up. I thought that would be a great idea for the large generators and air compressors that fire up and immediately go to wot. But after being around equipment like that for years at a time and seeing the oil sample reports I realized they were trying to sell something for a problem that doesn't exist, some of these pieces of equipment sat for months maybe years between jobs.


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