Transome leak
 

if it happened after the bellows were changed then it is possible it was put in wrong. on the drive side there are two ribs with a groove between them. a lot of people put it in thinking the lip in the helmet goes in the groove but both ribs have to be in the helmet. other wise it is not in far enough for the drive to press against the rubber of the bellows and make a seal. water then seeps between the helmet and drive and in past where it should seal to the bellows. just a thought but have run into this several times.

Leak
 

It could be the drain plug. Maby not the plug but the fitting screwed into the transom for the plug. Dry the transom and see if the water leaks out around the plug...

I have a 24' outlaw it had a leak , turned out to be the seal around the steering pin, I replaced the steering pin with a stainless pin , it came with a much better steal .

I'll throw in my .02 as I pulled my motor last winter due to a mysterious leak that I found with a endoscope camera and it turned out to be the y pipe o ring where it mounts to the inner transom assembly (not sure if you have silent choice or not). I would suggest buying one of these endo scope cameras and use your phone or a tablet. I backed it in the water and used the camera to find it, and I would run the motor too if you cant find it at first. As mine was significantly worse while it ran. They are worth the money especially after multiple seasons of changing things that did not fix it.

Guys thank you for all your input on the subject matter. I hope I can solve the mystery come this spring. Thank you again.

From my diary of knowledge from previous posts: Gimble Area Leak Points- Trim hose manifold, water outlet, cooling hose
connection on housing, steering pin.

I found a leak where the Captains Choice pipe connects to the exhaust wye pipe. The typical cheap hose clamps couldn't provide enough torque to make a seal so I upgraded to Awab style.

Keith

Transome Leak
 

I’m also dealing with a similar problem...

I have a 1990 Mercruiser Bravo 1 stern drive on my 1990 boat. I have a water leak I have so far not been able to trace, but I can tell you what I’ve done so far, and what I can see.

All of the rubber engine hoses are brand new, with brand new high-end stainless clamps so no leaks where the raw water comes through the stern making its way to the raw water pump or anywhere on the engine.

The water pump has been removed, inspected and cleaned. The oil cooler has been removed and inspected with no problems identified.

The engine cooling system does not have a heat exchanger, water from the source, lake or ocean passes from the outdrive to the raw water pump, through the engine and back out the normal course through exhaust risers, connected to a “Y-pipe and to the outdrive through the prop. The system does not have Silent Choice, all exhaust is through the “Y-Pipe” and out the prop.

I can see water running into the boat on the bottom side of the cutout for the drive under a couple of circumstances. If the boat is in the water, I can see water coming into the boat at a rate I am estimating ½ gal/min. The water leaks in at the same rate whether or not the engine is running when the boat is in the water.

When the boat is out of the water, I hook up “cuffs” to flush the engine if I have been in salt water. If I turn on the hose leaving the engine off, no water leaks into the boat. However, if I start the engine with the cuffs on and water supplied to the cuffs, I see about the same ½ gal/min leaking across the bottom side of the outdrive cutout in the stern.

Two years ago, I had the “bellows” for both the drive shaft and exhaust replaced. Also, at that time the external rubber hose between the outdrive and stern for the raw water intake was replaced. I’ve dropped the outdrive and inspected the bellows looking for any tears or leaks that might allow water to enter that area and into the stern cutout. The repair was done in a reputable shop. Inspecting this area from inside and out, I cannot see any obvious problems. Since the bellows replacement, I have put about 15 hours on the boat/engine. The boat/engine only has 610 total hours on it since 1990.

The Bravo 1 outdrive does not have a gasket, however, there are three O-rings. One is for the shifter, one for the outdrive lubrication and one for the raw water. The gaskets were old, so I ordered out new Mercruiser gaskets and replaced them. The mating surface for the outdrive was clean and shows no evidence of any corrosion or weak spots, so I am confident there are no leaks between the raw water intake and chamber with the driveshaft. The boat has a lot of years on it, however, 95% of the time it has been in fresh water.

Ok, so where is the leak, or better yet where should I be looking? Does this sound like possibly the Y-pipe O-ring? I see suggestions to use a borescope type camera which sounds like a good idea before I go about pulling the engine. Any suggestions are welcome.

IMO this is the most revealing info concerning your problem . I would have maybe suggested examining the water transfer grommet in the transom plate that is prone to crushing and creating overheating problems with the Bravo setups but if it was that it ought to leak as soon as you turn the water pressure on . I'm sure that someone will come up with a suggestion or two.
And I presume that you really mean 'muffs' not cuffs .. as in flushing (ear) muffs .. :)

Madbouyz, thank you for the reply....and yes, I meant flushing "muffs".

I agree, if there was a problem with water transfer grommet in the transome plate, I should have seen water running in when water pressure hits the area. The fact that it does not leak until I start the engine is suggesting to me the water pressure gets as far as the raw water pump, but not past it when the engine is off. When I start the engine, I'm now pushing water through the entire system. I did have the engine out a month ago and visually inspected the "Y-pipe" and there were no holes corroded through it that I could see. This has me thinking the problem might be the O-ring where the Y-pipe mounts down at the transome.

My best bet as far as I can determine would be to get a visual on the problem area, probably by using a borescope or similar. I've tried with an inspection mirror and just cannot get a good angle to really see the area closely.

It sounds like the Y-Pipe when the water is returning or the pressure drawing from the system is enough to expose the leak. One or the other

That's about where I am.....I've heard the O-ring at the Y-pipe joint can fail. Will let you all know what I find when I can dig into it.....thanks.

I had a similar leak and it was the o ring in the Y pipe. I think age and if it was ever overheated causes it to fail.

Donzi1979, thanks for the input. I am the sole owner of the boat and I'm confident it has not been overheated. The engine is a 7.4L, so we are not talking super high performance. The Bravo 1 should be a conservative outdrive for the 330 HP engine. The engine has rarely ever seen redline and I typically cruise at 2,700 to no more than 3,300 RPM. But age is another thing, 28 years. The O-rings on the outdrive were pretty stiff around the raw water inlet and lower drive unit oil connection, so it makes sense the O-ring to the Y-pipe could be the problem. For all I know the Y-pipe at the junction may have an issue. I'll have to take it apart to see what I find. Thanks for the input, this feedback is all helping me to point/head me in what I hope is in the right direction.