View Full Version : Transom leak

06-20-2006, 03:53 PM
Hi guys. I'm looking at an 86 z-25 with 535 hours. I noticed a trickle of water continuously running in where the trans connects to the stern drive through the transom. Do you have to pull the engine and the stern drive out to replace the gasket? Is there something else it could possibly be? I asked the mechanic at the marina and he said he thought that was the only way to fix it. Thanks for any input.

06-20-2006, 08:01 PM
Hi Brian: I think you have to be more specific about what drive you are looking at and what engine. However: The year you mention may be important...20 yeras old. I have an '86 Minx that developed a minor leak two years ago "somewhere" around the drive. The "Gimble Housing"...I think that is the name of the largest metal piece of the drive that makes direct contact with the transom...on the outside. This was originally bedded to the transom with a white compound that becomes dried up and powdery and starts to fall out. I took some black silicone seal (matches the Alpha I) and laid a very small bead clear around the gimble housing on the outside. That pretty much solved the leak problem. The following year I replaced the drive shaft bellows. That's a much-much larger task.

There are some guys on this board who are/were professional boat mechanics. They will probably have further info if they care to weigh in. John

David Ochs
06-20-2006, 08:23 PM
You have good advice from both of these people. Your mechanic is correct to want to remove the transom plate,(as I call it) just to see if any damage(rot) has occured. The gasket should keep water out at that point. However, I have had experience with water entering through the the bolt holes that attach that plate to the transom. I loosened the bolts and a tiny bit of silicone behind them and that took care of it. Also as John has mentioned a thin bead along where the shield and the transom meet is good insurance also. Keep in mind that gobs of the stuff look like crap and is not neccesary.
Good luck.

06-20-2006, 09:49 PM
Thanks for your replys. I have not bought this boat yet, still trying to decide. It is an 86 z-25 with 454 and trs drive. The trans is a velvet drive. The guy who owns it says he just had the bellows replaced. In the worst case, if it is gasket where the drive connects to the trans, I'm trying to figure out if the engine and trans has to be removed to fix it. I have read all of the posts that I can find on this boat and have learned lots of things I would never have thought to look for. Thanks to you guys, I knew more about the boat than the guy who owns it now.

06-20-2006, 09:54 PM
Well, just hope its not this 5,000 dollar problem...:eek!: :eek!:

Mr X
06-20-2006, 10:00 PM
Nice, did that come from Mel Fishers "Treasures of the Atocha museum" ?

06-20-2006, 10:08 PM
Actually the guys boat, a 92', was and kept it in great shape with regular service....Boggles the mind how that large of a hole could have happend...

06-21-2006, 12:01 AM
Actually the Alpha on the Minx when I bought it had a hole that was filled with caulk!!!!!!:(
I bought another on eBay and it looked like Brandons pic, only smaller. The seller had painted it for the photos. I was able to get it welded. It's still there and doing very well, thank you.:)

06-21-2006, 11:24 AM
Brings to mind a phenominon that practically no one pays any attention to and that's "Electrolysis". It makes your battery work, and will also eat up aluminum or any similar metal faster than you can imagine. Take a boat with an aluminum outdrive and tie it up near a "steel" sheet pile bulkhead and you can almost see the aluminum dissolving away. In fact, if the aluminum is unprotected, let's say the skeg, just put on a scuba mask and have a look. You may just see the bubbles. Warm salt water is excellent for accelerating this process.

Bronze is one of the "Superior" metals to resist corrossion, and Aluminum is one of the most "Inferior." If you put a superior metal "near" an inferior metal, add some nice warm Salt water and you've got a real problem. If the surface area of the superior metal is much greater than the inferior metal, the inferior metal will dissolve at an even greater rate.

One of the biggest mistakes people make is installing "their own" Battery Charger in the boat and charging the battery while the boat is in the water. A battery charger on the dock has the same effect. "Bubble Bubble". :bonk:
Suprising how many people "Think" they KNOW how to do it correctly. John

06-21-2006, 12:49 PM
Hey DonziJon. I have a picture of the stern drive. Tell me what you think. This boat has spent its life in Lake George, no salt.


06-21-2006, 01:01 PM
Man it has a lot of burn more so then most salt ones out by me, there may be stray current getting into the water from dockside power. Not sure but it looks like someone caulked around the transom shield it may have been leaking, if it has the wood core may be shot. Take a 1/2 dollar and tap the transom near the drive see if it sounds kind of dull, then tap outward to see if and where the sound changes. You need to do some serious investigation on this one.


06-21-2006, 02:57 PM
MOP is right. Stray current in the water can come from anywhere. Quite often you can never find out where. A couple of years ago I was tied up to a motel dock up in the Thousand Islands on and off for about a week. There was a "pump house" about 50 feet down the dock from where I was tied up and it must have been wired incorrectly, which I figured was the cause for my outdrive "shedding" All the paint on the skeg which I had repainted a few weeks before. Of course it's possable I wasn't meticulous enough when I did the paint job. You never know. It doesn't have to be SALT water either, although salt water is the worst. Any dock wired for "shore power" is suspect, especially if the wiring was done by an electrician who is NOT familiar with marine applications. :confused: John

06-21-2006, 03:15 PM
I didn't notice any obvious signs of water leakage that had been long term. The guy had obviously not had time to clean the boat so I don't think there is any attempt to try and cover anything up. If the gasket has to be replaced does the engine have to come out? Are there any other obvious things that could be corroded and if the damge is cleaned up and repainted would it be ok? There aren't many z25's for sale, so not much choice. I don't won't to buy a lemon either! Thanks guys.

06-21-2006, 07:41 PM
Hi Brian: When it comes to spending money, My Personal Doctrine has always been: "When In Doubt..Don't." This has always worked for me and I've never regretted the "Don't" decisions. I'm 64.

Oh Wait: Back in 1964 I had the opportunity to buy a 1954 Ferrari 250 GT Europa for $3800. I was just a Navy Puke and really didn't have the "Cash" on hand to make the purchase.. SO: I didn't. According to NADA, that car is now worth $411,000. What does NADA know anywho??? John :cool!: