1990 Welcraft 186 eclepse 4.3 liter Mercruiser Alpha 1 Gear oil ???

What causes gear oil to get into the hull?Looks to be coming from the drive shaft area.Is there 0-rings on the drive shaft spline/yoke?Or a rear seal for the drive shaft?

To me I would think in order to get gear oil coming in the hull that's alot of area & travel.Thinking that the drive shaft bellows must be filled up all the way with gear oil in oder for this to happen.
I don't have a sterndrive gear oil reservoir.There should be a way to check gear oil level but,I don't see how.I changed the gear oil the other day.So,I know it's fresh gear oil in the drive.But,how am I getting gear oil in the hull?
This sterndrive has a drive shaft some what like a car transmission.When a car tranny leaks at the driveshaft means rear seal is out.Same thing with a drive axle o-rings shot.Question is,Is there o-rings or a rear seal or both in this type of transmission drive?

Re: 1990 Welcraft 186 eclepse 4.3 liter Mercruiser Alpha 1 Gear oil ???

Your input shaft seal is the culprit on that one. You probably need to change that and your input shaft. Many times the seal will wear down a grove in the shaft itself. Its a fairly easy and inexpensive fix.

Without having the serial to your drive this is is just a guess. More so you have an idea where to look:

Oil seal: http://www.iboats.com/Oil-Seal-Sierra/dm/view_id.171683

input Shaft Yoke: http://www.shipstore.com/SS/HTML/710-/710-46020T02.html

Re: 1990 Welcraft 186 eclepse 4.3 liter Mercruiser Alpha 1 Gear oil ???

May I ask where,is the input shaft seal located?

Re: 1990 Welcraft 186 eclepse 4.3 liter Mercruiser Alpha 1 Gear oil ???

http://www.mercurypartsexpress.com/us/parts-search.html#epc::md718597mr1408ar13642

When you pull the drive off, look at the back and you will see the U-joint. There is a long shaft after the u-joint and a short shaft before it. The seal is located around the smaller shaft. To remove it you will need to remove the 4 screws on the top cover of the upper unit and remove the cover. You will see a nut holding a gear onto the shaft. Once you remove that nut the shaft will come out. When you remove the shaft, look at the part of the shaft that rubs on the seal. You will be able to tell right away if its worn or not. The seal needs to get changed no doubt, you might get lucky and be able to salvage the input yoke. I had to change both of mine. I also put a new set of u-joints on too just because...

Re: 1990 Welcraft 186 eclepse 4.3 liter Mercruiser Alpha 1 Gear oil ???

Your much better off using the "original" oem seal that is now National 712250 (483323VGO)

Re: 1990 Welcraft 186 eclepse 4.3 liter Mercruiser Alpha 1 Gear oil ???

Thanks everyone!You all been a great help for us newbies.
About the gear oil,one would think one would install a dip stick to check oil level after so many yrs of Mercruisers.Maybe they have in the new date units.I see some of the newer units have a oil reavoir.As my older 1990 don't.Makes things more difficult almost uncalled for.Whe ever designed these sterndrives took their money and ran.Thinking about this stuff now,The number 1 reason for water getting in the unit & oil leaking is because of rubber seals.Rubber seals can only hold so far until rubber seals gives way.The way they designed the system is if the sytem is under pressure from heat or water over flow causes the rubber seals to blow.I'm a motor head not a boat head.But,there's know difference between a rearend pig on a car/truck then on a sterndrive.They all have spider gears & 80/90 weight gear oil inclosed.Rear end pigs have over flow & or vent caps.If sterndrives had a over flow or vent caps installed the seals wouldn't blow from pressure.If water leaks into the sterndrive unit from a bad seal raises the oil level causing pressure & nowhere for the pressure to go/release other then blowing a seal.Gears get hot,oil gets out.Rubber doesn't like heat.If a hole was drilled into the unit housing & a hose/tube was attached with a vent cap (out of water).Would give release of heat & pressure.Transmission on cars/truck have these vent caps.Same with rearends.Engines have them as well.We call them PVC Valves.Without sterndrive vent release caps is why a pain to fill them on oil changes "No vents for oil flow".A faster a easier way to install new gear oil without a pump is I found simple to do & fast.Just like blowing up a basket ball.Use a ball niddle.Insert it into the qt of oil giving a little air.5 minutes tops 1 1/2 qts and your over flowing out of the overflow screw hole.Too much air will cause the qt of oil to blow in your face & cause a seal to blow.But,a little at a time will do the job.Much faster then any pump.Were,talking 89/90 gear lube at 5 minutes tops .That's something amazing to try.
Best people,