Bellows Replacement??

vndkshn

Cadet
Joined
Mar 30, 2012
Messages
20
So... I have a water leak.

Can't tell for sure where it is coming from, looks like it is entering the bilge from a pretty low spot on the transom area, around the drive somewhere, I just can't see where.

Its a 1996 7.4L with a Bravo 3.

When I put the boat on the trailer and look from outside, I can see what appears to the exhaust bellows (large, oval and flared rubber tube that lines up with a similar oval connection on the drive when the drive is down, but doesn't connect when the drive is up). That looks pretty dry and cracked on the part "outside" the boat, I can't see the part under the engine cover, its buried. Above it, I can see what looks like is probably the drive shaft bellows, it looks pretty dry as well, but I haven't found any actual cracks. I can see caulking around the entire gimbal housing, that largely looks ok. From the engine compartment, I cannot see any water running into the area around or above the driveshaft. As well as I can see, I don't see anything running in from the perimeter either. So... I am suspecting the exhaust bellows... but it appears there is a shift bellows as well, I just haven't found it yet.

I started flipping through Service Manual 16 (which is the one that applies to my serial) on boatinfo, and is pretty cumbersome on their site, so I haven't found the appropriate section yet. But per the Seloc manual I have, it seems this can be done with the outdrive still on, just more difficult, but they rate the whole thing as difficult anyway. It looks like the part isn't too bad, so I am thinking of trying to replace it, especially if I can do it without pulling the drive. If I have to pull the drive, I'll probably wait for winter. At this point, the bilge pump runs every 5 to 10 minutes for 10 to 15 seconds, and I've never run into any issues with the pump (its new this year) or with water getting to be more than a few inches deep back there.

So, other than the tool (buy or make), the part, and the adhesive... what else would I need and how much am I biting off with this?

Or based on the information, could it be something else? Not sure if the bellows goes all the way through the housing or not, tough to tell from diagrams, etc.
 

MarkSee

Lieutenant Junior Grade
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Sep 10, 2010
Messages
1,172
Re: Bellows Replacement??

Service manual 28 is for Bravo drives as if you look that up, you can get some pictures on things with the drive.

The oval exhaust you have is called an "exhaust tube" and connects only to the transom.
This would not be an entry point for water into the bilge.

What you probably want to do is pull the drive and look for any signs of water in the u-joint bellows.
This will also give you a chance to look at the gimbal bearing. align the drive, etc.

The shift bellows will be on the starboard side and pretty visible with the drive raised and you should see a gray cable.

Mark
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Bellows Replacement??

16 is the engine manual, 11 is the drive manual you want for the drive. Section 4A covers the bellows.

Pull the outdrive and check for water in the ujoint bellows. The exhaust bellows could be removed from the boat and you won't get water inside the boat.
If your leak is around the edge of the drive, you probably have a rotted transom. If it's the exhaust Y connection, you have to pull the engine to get it off and fix it.
 

Reel Poor

Vice Admiral
Joined
Jan 29, 2005
Messages
5,522
Re: Bellows Replacement??

Before you can fix the leak you have to KNOW where the leak is. It's not always easy to see but you have to find it. Try using mirrors, digital camera, phone camera, or have an eyeball installed on the end of one of your fingers and have a look around.

Possible areas of concern;
transom plate
drive shaft bellows
shift shaft bellows
water inlet hose or fitting
exhaust Y-pipe gasket
 

vndkshn

Cadet
Joined
Mar 30, 2012
Messages
20
Re: Bellows Replacement??

So I got a little extreme.

Had the boat out after taking a trip to a neighboring lake so I left it on the trailer for a few days. Put the plug back in it, put the water hose in the bilge and turned the water on, bilge pump off.

Found the vast majority of the leak was coming from the lower part of the gimble mount, the caulking was not sticking to the transom. Alot was coming from behind what I think is the Mercathode unit (at the very bottom, mounted to the block the lines for the trim cylinders connect). Removed the unit at the bottom, cut the caulk up to the area I knew was good and applied new caulk. Let it sit for a day then back to the lake.

While the bilge pump used to run every 5 to 10 minutes, I saw it run TWICE during a two hour plus afternoon on the lake. Think that definitely narrowed it down.

I did see the draft shaft billows is getting pretty ratty looking, it doesn't appear to be cracked all the way through, but it is developing cracks for sure. So that will definitely be a winter project at the latest. There doesn't appear to be any water coming in from that area, that area is dry in the engine compartment.
 

muc

"Retired" Association of Marine Technicians...
Joined
Jul 7, 2004
Messages
2,170
Re: Bellows Replacement??

Sorry to have to tell you this.

I know you don’t want to hear this.

My guess is you won’t believe me.


But ---- you have a rotten transom that will get worse.
 

vndkshn

Cadet
Joined
Mar 30, 2012
Messages
20
Re: Bellows Replacement??

Understand what you are saying, but there are other circumstances involved that I haven't mentioned yet.

I know there was work done before i bought the boat that involved removing the engine (new stringers), its possible the quality of the overall work l is the root cause. We've already fixed several things that are related to them not doing that properly (from the speedo hose not being hooked up, to the wiring harness not connected properly, to missing cotter pins, I could go on, but you get the point).

Still going to look into it further, likely later in the year as part of my winterization.
 

muc

"Retired" Association of Marine Technicians...
Joined
Jul 7, 2004
Messages
2,170
Re: Bellows Replacement??

I?m just saying that after 30 years in the boat business.
When you have to caulk the transom plate.
99.9% of the time the transom is rotten.
Hope yours isn?t. But it might be good to check it.
 

ENSIGN

Lieutenant Junior Grade
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Jun 21, 2009
Messages
1,179
Re: Bellows Replacement??

The caulk will not last! At a minimum you will need a new transom seal.
 

vndkshn

Cadet
Joined
Mar 30, 2012
Messages
20
Re: Bellows Replacement??

Yeah, if it holds me for a few months longer, I'll pull the whole outdrive this winter (already part of the plans for this winter) and check everything out.
 
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