Mercruiser Bravo transom leak

[jointventureII]

Dear forum,
Got a leak, a drip every 2-3 seconds, coming from what appears to be the top of the exhaust on my Mercruiser Bravo.

Is there anywhere other than the steering pin that could leak only when the engine is running?

Some points:
1) steering pin is stainless and new, installed Feb this year
2) steering pin seal is new, installed Feb this year
3) grease nipple fitted to grease the steering pin shaft so there is plenty of grease
4) also installed the JR marine access window but having stuck a video camera into the top of the transom assembly (where the steering pin lives), that's not leaking either
5) new bellows, both u joint and shift cable, were new Feb this year.

The hole through which the trim sensors pass is fine and I assume any leak from the exhaust would be there whether engine on or not?

I'm stumped, the only thing I can think of is the actual transom assembly seal (between the transom assembly and the boat...) is failing but above the waterline

 

[Portofino]

There was a thread not so long ago similar .
Boiled down to soggy transom .When the engines on the pressure from moving + vibrations squeeze water out .
Something along those lines …explains why it’s above the WL .

 

[spannerman]

Its not the pitot connection for the speedo if fitted, if no speedo there should be a plug in the quick release connector.

 

[volvopaul]

Bellows leaking , there’s a small hole that allows water past into the boat to tell you there is a problem.

 

[jointventureII]

Thanks all!

The investigation will continue, it's only occurring when running and it's fairly instantaneous.

The speedo tube outlet was completely dry - it's right on the waterline so I was certain that was the cause when spannerman mentioned it, no joy.

Bellows will be checked when lifted next month but wouldn't that occur all the time?

 

[spannerman]

I had the exact same problem on a Hydrolift, it only leaked underway but that is when there is water pressure on the pitot inlet and up to the connector. You need to be back there with a light and a mirror while someone drives to be sure.

 

[jointventureII]

So I got an endoscopic camera and had a good look.

Leak appears to be u joint bellows but only when engine running. Boat is kept in the water full time but it doesn't leak when engine isn't on. Upper sections totally dry and no signs of water intrusion. I shut the engine off and tilted the leg fully up which caused a momentary small stream of water, lasting 5 seconds, which confirmed it.

How can this be? Vibrations causing the gap between sterndrive and bell housing to seep water in?

 

[Elessar]

So I got an endoscopic camera and had a good look.

Leak appears to be u joint bellows but only when engine running. Boat is kept in the water full time but it doesn't leak when engine isn't on. Upper sections totally dry and no signs of water intrusion. I shut the engine off and tilted the leg fully up which caused a momentary small stream of water, lasting 5 seconds, which confirmed it.

How can this be? Vibrations causing the gap between sterndrive and bell housing to seep water in?

Get it out and change the bellows sharpish. It isn’t going to heal.

Porto’s concise and accurate post was a real possibility. Thank your lucky stars.