Priming oil after rebuild

[sanibel sailor]

No data but it seems that most marine engines die from catastrophic events- overheating/water in cylinder, etc or from disuse- sitting for long periods without being run, rather than from “wearing out”. While it won’t help with preventing damp salt airin the combustion chamber, I wonder if prelubing might help for engines that have set and had all the oil return to the pan.

[a64pilot]

Pre-lubing doesn’t hurt and of course can often help.
Your case of an engine sitting for a long time for example.
All I’m saying is there is no evidence to back up the claim that it will make your engine last much longer than an engine with no pre-lubricator.

I wish it did, I’d have one.
Pre-lubers came into fashion about the same time that high bypass oil filtration did. High bypass oil filtration of course filters oil down to a very, very fine level removing almost all wear particles.
It also sounded logical that it would greatly extend the life of an engine, unfortunately actual experience doesn’t back that up, apparently below a certain size particles cause little wear on an engine and filtering smaller than that size doesn’t do as much good as we would hope.

While many die from catastrophic events, I still think many wear out, many that wear out would have lasted much longer with better preventative maintenance, something that most engines don’t get.

It’s interesting that a new engine will usually get frequent oil changes etc, but older ones do not, but new engines don’t need frequent changes as often as older ones. As engines get old, blow-by increases and the blow-by contaminates the oil with combustion by products of course, so the older the engine is, the more frequently it’s oil should be changed if your trying to max it’s useful life.

A lot of our engine knowledge and practices comes from automobiles, and rarely does a modern auto outlast the engine in it, most often the car itself wears out and or the electric engine controls etc wear out and the car is replaced, with the base engine still in decent shape.
20+ yr old cars are uncommon, 20+ yr old boats are not.

[AKA-None]

Originally Posted by a64pilot

....

Actually it’s the cam and lifter that see the greatest stresses, ...

This is a killer so make sure you put some moly on the cam

[sailorchic34]

After I rebuilt my yanmar 3gm30f in the cockpit back in my summer of discontent in 2013, I simply pulled the decompression levers and cranked for a bit till the rockers had oil. I had of course lubed all the new bearing prior to assembly with stp. I'm so old school.



Assuming you have not primed the fuel system, yet, just crank for 10-15 seconds, then prime the fuel system. I found that priming the fuel system took quite a bit of time and more then a few cuss words (I call this chanting).


My engine is going on 800 hours now.

[Gounkoto]

Originally Posted by ggray

While we are talking about "truisms", might be a good time to ask about one.

*Filling the oil filter when changing the oil.*

Does this really do any good?

Good practice. It will reduced the engine oil pressure build up time by few seconds.

[stormalong]

Originally Posted by Gounkoto

Good practice. It will reduced the engine oil pressure build up time by few seconds.

IMHO Warming up the engine which circulates the old oil and coats all of the engine parts in more important than filling the oil filter. That way the engine is lubed during the few seconds it tales to fill the oil filter. Pre filling the oil filter is impossible on many engines with horizontal spin on fiters.

Plus it is a good idea to warm up the oil before you pump it out.

[leftbrainstuff]

Originally Posted by Gounkoto

Good practice. It will reduced the engine oil pressure build up time by few seconds.

Absolutely. Nearly all engine wear occurs before oil pressure is up and all oil galleries are full and flowing.

Of course with a preoiler I dont bother filling the filter.

[leftbrainstuff]

No evidence for preoiling???

A decade in F1 and hundreds of engine rebuilds indicates otherwise. There is many decades of evidence from the likes of Caterpillar, Rolls Royce, MAN, Mercedes, BMW, etc.

There is also a wealth of information from the Merlin V12 engine development during WW2. That engine suffered many failures until lubrication problems were sorted.

My dad is also a diesel mechanic and he has seen many more million+ mile engines than I. It was his experience that led to me digging deep on this topic throughout my career.

Some of my earliest memories, with my dad, stem from micing up bearing shells and journals during engine builds and tear downs. Many of these engines he looked after from build to teardown.

Pre oiled engines retain their bore cross hatching and dont suffer the visible bearing wear that engines run dry and with degraded oil do. Just as important as pre oiling is frequency of oil changes. Both have similar effects.

as for 20+ yr old auto engines being uncommon? WTF. Most of my non motorsport career was spent restoring 30+ yr vehicles, including many pre war exotics. There are just as many tired, abused marine engines as there are car and truck engines. The only significant difference is salt water.

As for the once trendy long life oils and filters well that was mostly marketing FUD rarely backed by good engineering.

[RaymondR]

Originally Posted by sailorchic34

After I rebuilt my yanmar 3gm30f in the cockpit back in my summer of discontent in 2013, I simply pulled the decompression levers and cranked for a bit till the rockers had oil. I had of course lubed all the new bearing prior to assembly with stp. I'm so old school.



Assuming you have not primed the fuel system, yet, just crank for 10-15 seconds, then prime the fuel system. I found that priming the fuel system took quite a bit of time and more then a few cuss words (I call this chanting).


My engine is going on 800 hours now.

Two good points:

You are going to crank the engine fairly extensively whilst bleeding the injectors and that should pump all the galleries full of oil before you actually get to start the engine.

and,

The proper application of both blasphemy and profanity is vital to the success of all boat engine work.

[jimbunyard]

Originally Posted by sanibel sailor

No data but it seems that most marine engines die from catastrophic events- overheating/water in cylinder, etc or from disuse- sitting for long periods without being run, rather than from “wearing out”. While it won’t help with preventing damp salt airin the combustion chamber, I wonder if prelubing might help for engines that have set and had all the oil return to the pan.

Yep, paradoxically many (most?) recreational marine engines 'wear' out from disuse rather than use...

[ggray]

To respond to this, and A64pilot

Originally Posted by Gounkoto

Good practice. It will reduced the engine oil pressure build up time by few seconds.

Yeah, that's what I always thought, but is it really true?

For it to be true, I assume the filter would need to be on the pressure side of the oil flow (between the oil pump and the pressure release valve??) but I think it filters the oil on its return to the sump.

I have noticed after oil changes that it takes longer for pressure to build than normal starts, even though I have filled the filter. I just figured that the passageways drain more completely with an empty sump.

I really don't know, thus the question.