Prelube setup

Ski in NC said:

I like prelubing engines that have sat for years, but not the ones that have sat for a few months.

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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.

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.

Northern Spy said:

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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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.

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.

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.

timjet said:

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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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.

psneeld said:

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.

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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.

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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