What is the diference in automotive and marine gear lubes? Can you use regular GL 4-5 Gear lubes?
Lower unit gear lubes
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I have used Pennzoil Marine 100% synthetic, Amsoil, Mobil I and Royal Purple Max Gear 75W90 rated GL4/5. I have had 0 problems with any of these. But I change my lower units twice a year and I only use 100% synthetic lubes in the lower unit. Now this is in Outboard lower units. I have only had one stern drive, Mercruiser in a Hydrodyne ski boat.
The problem with tacifiers is operation in cold water. If the water temp is 40 degrees, the lube stays very tacky until it reaches aboout 120-130 degrees. This can cause alot of drag on the power plant and the lube may never fully liquify while running. Again my experience is only in outboards.
The problem with tacifiers is operation in cold water. If the water temp is 40 degrees, the lube stays very tacky until it reaches aboout 120-130 degrees. This can cause alot of drag on the power plant and the lube may never fully liquify while running. Again my experience is only in outboards.
Here's an odd-but-related question:
Someone told me that you aren't supposed to drain lower unit fluid out through the bottom but pump new fluid in through the bottom and flow the old stuff out through the top hole. Draining out through the bottom supposedly leaves behind water/moisture.
Any of you serious boaters ever heard of this? Is this some sort of lame April Fool's joke?
--- Bror Jace
Someone told me that you aren't supposed to drain lower unit fluid out through the bottom but pump new fluid in through the bottom and flow the old stuff out through the top hole. Draining out through the bottom supposedly leaves behind water/moisture.
Any of you serious boaters ever heard of this? Is this some sort of lame April Fool's joke?
--- Bror Jace
Bro,
I have never heard of that. I think it could work, but as you are pumping in the new fluid, it could mix with the old. Also I drain my lower units in a clean pan, and I can check for visible metal and moisture. Then you pump the new fluid in from the bottom and it comes out the overflow. So you are back flushing to a point. Just my thoughts, but not an expert on this.
I have never heard of that. I think it could work, but as you are pumping in the new fluid, it could mix with the old. Also I drain my lower units in a clean pan, and I can check for visible metal and moisture. Then you pump the new fluid in from the bottom and it comes out the overflow. So you are back flushing to a point. Just my thoughts, but not an expert on this.
"Then you pump the new fluid in from the bottom and it comes out the overflow."
Maybe that's what I heard ... and extrapolated the rest.
After draining, couldn't you fill from the top until it starts to come back out the check/fill hole? That's the way I'd do any manual gearbox.
--- Bror Jace
Maybe that's what I heard ... and extrapolated the rest.
After draining, couldn't you fill from the top until it starts to come back out the check/fill hole? That's the way I'd do any manual gearbox.
--- Bror Jace
Most manufacturers suggest that there is too much opportunity for air to get trapped in the casing if it is filled from the top. My OMC manual says to fill from the middle plug instead of the lower one.
What do you use to pump the gear lube in from the bottom?
You can purchase a pump from most stores that handle marine products, and also at Wal-Mart. Cost is about $7.50 and they last until you lose them. They are 99% plastic, but work with no problems. The pump has a hose on the top that screws into the drain hole. You leave the vent (top) hole open and pump it up until it comes out the top. Then insert the top plug, and remove the bottom hose and insert the plug there. Very little lost doing his.
After I complete the fluid exchange then one thing I do is clean both the drain and vent holes with a good cleaner such as brake cleaner or a strong detergent, then the next day or when it is dry, fill the cavity over the drain plug and the vent plug with GE clear silicon. When I am ready to change the lower unit oil again, I spray the silicon with any cleaner used to loosen bolts, and let it sit for 24 hours, then the silicon comes out and cleans off.
Just my way of doing it.
That someone that told you this, does there boat still run?quote:
Originally posted by Bror Jace:
Here's an odd-but-related question:
Someone told me that you aren't supposed to drain lower unit fluid out through the bottom but pump new fluid in through the bottom and flow the old stuff out through the top hole. Draining out through the bottom supposedly leaves behind water/moisture.
Any of you serious boaters ever heard of this? Is this some sort of lame April Fool's joke?
--- Bror Jace
if you let the lower unit sit long enough, all the water will settle to the bottom of the unit. So when you pull the "drain" plug, which is on the bottom of the gear housing, water will come out first before oil if there's enough present to separate out. The "vent" plug, on the top of the unit, is there so when the gearcase is being drained of oil air can enter so the oil drains out. Otherwise the oil when draining would pull vacuum inside the outdrive and with the oil being such high viscosity it would take forever to drain out. The same goes for pumping fresh lube in. If you pumped it in from the top, it would take forever to fill the unit while letting the air escape out the top vent hole. Pumping lube in at the drain hole in the bottom lets you fill the unit quickly and correctly, forcing all the air out the vent hole, till fresh lube runs out the vent hole. This way, there is no air in the gearcase.
There is an outdrive gear lube pump, around $10, which has a fitting that'll screw into the drain plug hole and allows you to pump fluid into the unit.
Pumping new lube in from the bottom when there's old lube in there does not guarantee all the old fluid comes out the top vent hole before the new fluid does, especially when only N quarts are pumped in and the capacity is N quarts.
Let me give you a first hand REAL experience with outdrives and no vent hole. When I was 16, many moons ago, Dad and I dropped in a new motor on his 30 footer. Took the outdrive out, old Mercruiser 888, and drained the oil. I put a new motor in and got the outdrive lined up. Used one of those old 12 ounce squeeze bottles that we see all the time to fill the outdrive up from the bottom. Well, I squeezed and squeezed, until I thought I had all the oil in it. It was July 4th, took the boat out to watch the fire works and Dad, being the party neighbor, brought some friends out that night. He asked me did I fill the outdrive up and I said "DUH!!!!" Well, you guessed it, about ten minutes into the trip, everybody about half lit, the outdrive goes. I'm like...***? Finally get towed home, take off the top gear cover on the outdrive and low and behold, that sucker was bone dry. Got a good @ss whipping that day. I've learned and have really been appreciated Mercruiser for putting in a vent plug. Everytime I change out the drive fluid, I always think of dear ol' Dad. He passed away in December so I'll be thinking of him this summer, you bet!!!!!!!
[ April 17, 2004, 09:45 PM: Message edited by: Schmoe ]
[ April 17, 2004, 09:45 PM: Message edited by: Schmoe ]
I agree with this proceedure that Tony outlines. Buy the pump and go with the Pennzoil Sunthetic. I am currently running it in the lower unit in my 115 Johnson. For $5 a quart, you can't go wrong, Joe
Powerboat magazine specified that the Bravo shop a high performance Bravo outdrive shop in Florida recommended using Mobil 1 75W-90 in their HP Bravo outdrives. This was confirmed when a local friend received his Bravo II and on a small tag it said filled with M1 75W-90 Gear Lubricant.
I can see the Bravo's getting M1 75W-90 because they are high performance beast and don't use dog clutches as the Alpha's do. The Bravo's have had bad track records in the past for gear failure. I think going to the M1 also provides some shock absorption benefits to when racing. At least for the Mercruiser outdrives, I don't know if I'd want to flush the drive with a solvent based cleaner. There are a lot of rubber, plastic and gasket material that would be exposed to the solvents. One word of caution on draining from the bottom, when your done pumping, have the fill screw in hand. As soon as you take out the pump, the drive fluid will come flying out of there and you need to be quick about putting that screw in. It's not for the "I don't want to get my hands dirty" type of mechanic. Also, the synthetic High Performance fluid stinks. I have in the past, whereas I didn't have the pump and was putting the boat up for the winter, just filled the reservoir up and let it slowly drain into the outdrive. Check it once a month and top off. By the summer, the drive will be full. But to make sure, I pop off the vent plug just to make sure the fluid is up to that mark.
Another hint. When you are filling from the bottom, after you have finished pumping, but before you remove the hose from the bottom drain, close/tighten the upper fill/vent holes. This will dramatically slow down the gear oil that drains out the bottom hole while you are putting the screw in. Good luck.
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