Im wondering if filling a syringe full of oil and inject it in the oil feed port of the compressor would work? Do this and rotate it around and add more untill it comes out the return ports. Then hook the oil feed hose back up thats primed right to the end. At that point the 90 degree fitting would be the only thing without oil on startup and that is maybe 1in long. Do you guys think this would work?
No.......There is more at stake than just the compressor......Crank bearing. Get a Oil Pump Prime Sequence Performed. Don't cut corners on a $16000 motor!
How are the crank bearings effected by this if you dont mind me asking?
I say no and Mercury does not claim it needs to be done in the manual.
Physically there is no benefit of priming vs lubing through the oil inlet fitting. The return lines to the engine might supply extra lube to the bearings but its not the main source and the return lines move as much or more air then oil in normal use.
The best way in my opinion would be to lube the compressor through oil inlet fitting before it was mounted. Then rotate the whole unit to distribute the lube to the piston and maybe the rod bearing.
Originally Posted by Savage
I would also think by doing that it would be distributing the oil better than just priming it. I planned on getting it primed but questioned the need for it after taking my old one apart. I noticed my feed line did not loose prime or syphen back down the hose. Also noticed those 2 return lines are the same size as the feed line. So there is no physical way those lines are full of oil at any given time. Also i believe the oil that is left in them at shutdown drains down the hose. I can't say this for sure but when i opened mine up the oil level was below the return hoses and there did not apear to be hardly any oil in those lines. But i think for good measure i would give each one of them a squirt of oil right before i hook them back up. I am no guru when it comes to this stuff thats why i ask questions. But this seemed pretty straight forward unless i am missing something?
Last edited by Mike82; 07-25-2017 at 03:57 AM.
I would get it primed but it is your money...
USN Retired
2020 Basscat Caracal
2020 Mercury 225 ProXS 4s
You say that but give no reason why. I started this post to be proven wrong. I see it this way but i may be missing something. Im all about doing it right. But on the same hand if i see a better way that doesn't cost a 100 dollars im going to ask about it.
I replaced my return line oil filters when i bought the boat. I did like everyone said and went and got a oil prime done for 100 bucks. Now that ive actually taken it apart i realize i definatly wasted my money doing that. So here i am again in a slightly different scenario. With more of a understanding of how it works and questioning it this time. I was hoping to get the reasoning behind it. Not so much a programmed response like alot of people do just because they read it on a post somewhere.
Armchair mechanics read something somewhere once and become overnight experts. Can lead to misinformed advice unfortunately.
Just gotta know who to trust.
I would seek Don's advice and ignore anyone who can't explain why something should be a certain way.
Or try searching for a post where it's already been discussed. Good luck!
I agree to let Don answer. In the mean time, I'll expound on my answer...and I am no expert but that does not mean I just read things. I DO things too. It is all risk/reward. You induced air into the oil system. We can all agree that it should be purged. I would have it primed and KNOW the air is gone. You want to take a more economical route but you are risking the entire cost of a rebuild or new motor. That is not worth the riak IMO.
Have you ever listened to an oil prime sequence? I have and it isn't just a couple of squirts of oil probably 30 plus. It takes way more time than I thought it would. Based on that experience, I would have it primed. But like I said, it is your money.
USN Retired
2020 Basscat Caracal
2020 Mercury 225 ProXS 4s
These lines are open to the atmosphere in normal use. Disconnecting them is not introducing air. Priming will only add extra oil into the compressor for initial start up.
The manual is written by the engineers that designed the outboard.
But, Mercury Technical Training recommends running an oil pump prime sequence.......
I guess this is a case where the Tech. knows better then the engineer.
From a thorough study of the system it would be no different then adding some oil to the compressor before it is installed.
The procedure is called priming the oil pump. This in its self claims it is used for when the oil pump or up stream of the oil pump is in a dry state.
Also rolling element bearings do not need a constant source of lube. It is a basic engineering principle. That is why they are used in these types of applications where is impossible to do so.
Engineers don't write the manuals......that's why they have mistakes and Service Bulletins are sent out to make changes/corrections.
Listen I don't care if YOU do the procedure, or not, but don't put other people's investment at risk with YOUR theories.
$100 isn't worth it and your no paying for their motor if a problem occurs.
Usually it is a combination of tech writers and engineers that write the manuals. Everyone has a theory. I try to stick with the facts and the manufactures support material.
Do you have any written proof that Mercury in anyway recommends that these OB's should be primed after replacing the compressor? Your obviously one of the boards Guru's and people take your word as gospel, but they might be spending money for no benefit. These outboards are so economically and labor intensive to keep running. I'm just trying to help the average DIY.
This information is INCORRECT. Leo... I've seen nearly a half-dozen threads with you conversing about air compressors, a subject you indicate you know a lot about.
Then... we see pictures where you finally realized your own compressor had failed with a wrist pin coming loose, correct?
I'm going to STRONGLY suggest you stick to advice on topics for which you have attended Factory Training.
If the oil lines are disconnected ANYWHERE after the onboard oil tank, for any reason, an oil pump prime sequence is required.
Replacing the compressor opens multiple oil lines, and introduces a potential of air in the lubrication circuit for the MAIN BEARINGS of the engine.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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Your not helping these folks save money when you go against what Don Weed (Mercury Master Tech) has stated numerous times, that after a compressor change an "oil pump prime sequence" should be performed. You can do it Via the shifter handle method IF you want to try and save money, but the plugs could become fouled and it will use more oil.
Sorry but Mercury doesn't allow documents to be reproduced and distributed on the Internet.
I stand by my statements. My compressor had two failures the rod journal and the wrist pin which was not a failure it was a manufactures defect. The lines are open to the atmosphere when installed to the compressor. Removing them makes no difference. You can't dispute that, it is fact. If you can supply some type of written explanation from the manufacture it would be satisfactory on my part.
They should send me a revision for my very expensive manual then.
You will never be privy to Mercury Service documents unless you are a Dealer, or technician...... or if you have personal friends affiliated with Mercury that are willing to share.
The automotive repair field is exactly the same. There are thousands of Service Bulletins, and Dealer only documents, that the casual owner will never, ever, here about, that pertains to their vehicle.
