frost plug starboard side of drive

[clearlakeboater]

Hi there, I have a 1973 larson lapline with a 120 hp mercruiser(alpha one?). This summer I noticed that the "mercrusier" sticker on the starboard side of the stern was falling off and that there was water coming out of it. I peeled the sticker off, and found a frost plug! I had winterized the drive the previous fall, and added new oil, so I assume that it didn't freeze. The drive seemed fine for almost two months! I drained the drive to find that there was water in it, and added new oil. Again it was fine for about three weeks, and then the plug was leaking water again. I think what is happening is that the stern is sucking water, pressurizing the case on the drive, popping the frost plug, and pumping the oil out of it, filling the case with water. Is this possible, is there a vent somewhere that is plugged? Any advice would be helpful. Thanks, Chris

 

[Don S]

Re: frost plug starboard side of drive

That plug is not for frost, but to hold the core during the casting process. It's not connected to the oil passages. <br />You need to remove the drive from the boat, drain the oil and do a pressure and vacuum check on the drive.<br />If you found water or a water/oil mixture in the ujoint bellows, then you have found your problem.

 

[clearlakeboater]

Re: frost plug starboard side of drive

Thanks for the reply Don, You'll notice that this is posted twice. I put it in the wrong forum the first time(rookie mistake). Another gentleman posted on the other listing, and you both are agreeing that I will have to dissasemble the drive to find the problem. Thanks for the info, and I'm sure that I'll be posting and searching more once I have the drive torn down. Thanks again, Chris

 

[DHPMARINE]

Re: frost plug starboard side of drive

clearlakeboater,<br /><br />You're close to being on the right track and I can try to help.It is a core (welch) plug you are refering to on the starboard side of your drive.It's purpose on older Mercruiser outdrives is to gain access to an oil drain plug for the upper drive.If your drive is one continuous resevoir,meaning the upper drive oil drains out thru the lower unit drain plug,you don't need to have access here. <br /><br />But because this core plug is underwater,and water can get into this area of the outdrive,water will get to your ujoint yoke oil seal.This seal is just like your crankshaft seals.They keep oil in,but are not designed to keep water out.(water is not supposed to be there).As long as water is there,it will get into the drive oil.<br /><br />Get a new core plug,and install it with sealer.(I use permatex type 2.<br /><br />If you continue to find water in your gear oil,then you have a seal problem to address.<br /><br />I think if you even installed a NEW outdrive you'll find water in it as long as the core plug is leaking,and water gets to this seal.<br /><br />Good Luck,<br /><br />DHP

 

[clearlakeboater]

Re: frost plug starboard side of drive

DHP, Thank you for the advice! I see what you are saying about the core plug being underwater, but I think under normal running, when the boat is running flat, I think that the plug is above the water. I guess I couldn't tell you where it is at out of the hole, it probably is under the water! So where is the oil going? Is it possible that the oil is going out the bottom seal? What would happen if the seal on the prop shaft was bad? Thanks for the help, Chris

 

[DHPMARINE]

Re: frost plug starboard side of drive

Clearlakeboater,<br /><br />The hole only needs to be underwater once,and it gets into the bellows/ujoint area.No boat momentum is needed for water to get in the drive.It leaks in.<br />It doesn't matter right now where the oil is going.We have to stop the water coming in first.<br /><br />DHP

 

[Don S]

Re: frost plug starboard side of drive

Wrong-Wrong-Wrong ! It does not go into the oil section of the drive, only the water.<br />The welch plug (#21) covers a plug (#22) known in the service manual as a "Pipe Plug, water pocket"<br />If you look at the diagram below, you will see it's in the water area of the drive.<br /><br />

 

[DHPMARINE]

Re: frost plug starboard side of drive

Don,what I'm suggesting is the water gets into the shift housing,and then into the bellows area.Once there it passes thru the u-joint/yoke seal,and into the gear oil.<br /><br />DHP

 

[Don S]

Re: frost plug starboard side of drive

It doesn't matter right now where the oil is going.We have to stop the water coming in first.<br />

While the leak does need to be stopped, the fact that oil is getting into the drive has nothing to do with the water leak. That shift cable cavity (if like 90% of the alpha drive out there) has water in it anyway just from leakage past the shift shaft seal and bushings which allows water into that cavity. The fact that oil is leaking out of the drive and water is getting in means there is a leak and the only way to find a leak is to pull the drive, drain it and do a pressure and vacuum check. And I agree, it could be going past seal (a) in picture below, but that is not because of the leaking welch plug. <br />Even if that plug was left completely out, water shouldn't get into the drive. The bellows may also have a hole in it, who knows how old it is.<br /><br />

 

[clearlakeboater]

Re: frost plug starboard side of drive

Thank you so much for all the info and thoughts on this problem. I can see both of you points, and it's obvious that the stern needs to be removed and checked out. The boat is quite old, and I don't know the last time the bellows were changed, probably 10+ years. I will try to pull it this weekend, check it out and get back to you guys. Thank you again for all the advice. Chris

 

[Don S]

Re: frost plug starboard side of drive

If that bellows is 10 years old, it needs replaced. No question about it.<br /><br />Remember one thing......Replace all gaskets and orings, and seal rings with new every time. They are not reusable.....EVER

 

[DHPMARINE]

Re: frost plug starboard side of drive

Don,<br /><br />I don't intend for you to take my posts seriously,but I also hope you read them.<br /><br />But I thought you would address my point about some seals only keeping oil in,not water out.<br /><br />DHP