Leaky y-pipe?

[500dollar744ti]

I have a 1990 mcm 350 magnum, dont have serial number at this time.

Water is intermittently trickling in at the top of the lower y-pipe horn. Does not happen when engine is running, only after running while still warm. After cooling down the trickle stops.

Boat is in salt water now, this is the third time ive had it in salt. I keep it in saltwater for a week at a time then it comes out. It has otherwise always been freshwater.

I took transom core samples and found one soft spot near a crappy transducer installation but everything around the drive is solid.

Put it in salt for the first time last year and shortly after i had to replace risers and manifolds from corrosion.

Does the y-pipe seal ever go bad or corrode away? Is it a wear item like the risers and manifolds?

Would like to diagnose it before I pull it out of the water tomorrow.

Thanks

 

[alldodge]

Re: Leaky y-pipe?

I've seen them corroid and wind up with large holes. Corrision strikes all over. Doub't if you can reach it but if you can see how tight the nuts are, but as before don't think you can reach them

 

[500dollar744ti]

Re: Leaky y-pipe?

I was able to reach one of the nuts and it was tight. I only have my phone and I'm trying to attach a photo of where its dribbling in but i cant seem to get it.

It's not enough to trip my bilge pump float switch over night but there is enough to concern me.

I want to pinpoint it but its hard to see. Frustrating.

 

[alldodge]

Re: Leaky y-pipe?

Mentioned it appeared to come from the top of the Y-pipe, is it possiable to come from the bellows or shift cable and leaking down from the top?

 

[500dollar744ti]

Re: Leaky y-pipe?

I found how to post a picture. Here is the water dribble.

 

[alldodge]

Re: Leaky y-pipe?

Is there a possiability it is coming from the intake water hose, under or beside the hose clamp? I see the water and while it is on top the Y-pipe could it be dripping down

 

[500dollar744ti]

Re: Leaky y-pipe?

Ill look into that. I'd love for that to be the issue. It won't be that simple with my luck. I took the boat out of the saltwater and bringing it home from the beach. I'd just love to find the leak on the muffs to show either an exhaust or water pipe leak.

 

[alldodge]

Re: Leaky y-pipe?

I hope it works out for you as well. When the boat sits in the water the pressure builds up and it could be the hose. You could leave the boat on the trailer and put it on the ramp for testing.

 

[500dollar744ti]

Re: Leaky y-pipe?

I don't think it's the intake water hose, it feels dry all around it. I'm going to run it one more time today and see if I can pinpoint something from the exhaust. There was some water gathering when I ran it yesterday but I don't know if that was residual from when it was still docked. It should be dry by now so I can check if anything drips from the exhaust. I went and got a telescoping mirror yesterday but it may be too big to see what I want to see.

After I run it I'll pull the drive and check bellows. Another possibility I can think of is I remember when I replaced the drive bellows, someone had installed one of those repair kits for a corroded area where the bellows attaches. It looked rather thin and I could see a possibility of further corrosion past where they installed the repair kit allowing water in. It could also be allowing water to get in the under the bellows where that area was corroded without actually getting into the bellows.

Ugh.

 

[500dollar744ti]

Re: Leaky y-pipe?

Okay better news since I always fear the worst case scenario. I took the drive off and pulled the bellhousing and drive bellows which does in fact have a small hole in it. When I installed the bellows at the beginning of the season, I made absolutely sure I didn't put a scratch on it while installing, I put it all on by hand, no screwdrivers.

I've put almost 100 hours on the boat this season but is that really the life expectancy? Other parts of the drive bellows looked cracked but not broken all the way through. Pretty sure I got conned into buying a Sierra bellows instead of OEM because they were sold out, that's the only explanation I can think of for the premature failure.

 

[alldodge]

Re: Leaky y-pipe?

Glad it's not the Y-ppe but a real bummer on the new bellows. I've installed sierra belows and have not had a problem but have heard others with issues. Everyone including Merc can receive a bad one. The old manufactures defect which doesn't make your outcome any different. I use both and haven't had a problem, but it's always the boaters decision. The pic looks like it was either pinched or rubbed trough.

 

[500dollar744ti]

Re: Leaky y-pipe?

I'm going to try the genuine Merc bellows this time, I'll use a Sierra gimbal bearing as I've had okay results with those.

 

[81 Checkmate]

Re: Leaky y-pipe?

From the pic.......Im with ALLDodge.........Looks like it was rubbed thru by something.

 

[CharlieB]

Re: Leaky y-pipe?

Bellows do have 'flats' and orientation must be correct during install. If rotated incorrectly it will rub.

I've used lots of Sierra bellows, never a prob.

 

[500dollar744ti]

Re: Leaky y-pipe?

The flat areas were properly oriented. It may have just been sea garbage that got jammed up in there. I've launched at an area that has all these underwater plants growing and their little branches for lack of a better word get jammed up around the bellhousing and I have to clean them out after running. Maybe a piece got jammed against the bellows.

 

[CharlieB]

Re: Leaky y-pipe?

Many of the OLD OMC's that trimmed the motor/drive combination and had that huge bellows at the transom, sank at the dock when muskrats chewed a hole in them.