I have a leak.

[Pmt133]

So I've been getting some water in my bilge since the rebuild. I've narrowed it down to what I believe are two unrelated leaks... one is the water pump bolt, which I know how to address.

The other, is the shift cable. And I've never seen it but that doesn't mean it isn't possible. What is happening is water is being forced through the cable core up to the shift interrupter/linkage attachment point and down on the valve cover then to the bilge. I pulled the drive, gasket is in tact as was the water passage o-ring. Alpha 1, 1984 M.Y. it seems the upper shift shaft seal is leaking. The shift shaft is grooved where the seal would ride so I'm replacing both the seal and shaft.

My question is this... is it reasonable to assume that back pressure and water flow from the exhaust is enough to fill the cavity in the bell housing and force it through the cable core? I have the exhaust tube not bellows so I'd have thought maybe not but it doesn't seem unreasonable to assume it could make it's way up the 14 inches of height or so to come out the cable end. It's in the shifter cavity so regardless of if it's the shaft or water tube o-ring, it's getting in there and I need to fix it.

I've pulled the cable core, blew it out and dried everything but I may replace the (new) cable out of precaution being I run in the salt...

Any other opinions on the matter are appreciated or if I'm missing anything. Thank you.

 

[Grub54891]

Following along, I've ever seen that happen and I've worked on alot of them. But the shaft/seal should be smooth. possible you are on the right track.

 

[Scott06]

So I've been getting some water in my bilge since the rebuild. I've narrowed it down to what I believe are two unrelated leaks... one is the water pump bolt, which I know how to address.

The other, is the shift cable. And I've never seen it but that doesn't mean it isn't possible. What is happening is water is being forced through the cable core up to the shift interrupter/linkage attachment point and down on the valve cover then to the bilge. I pulled the drive, gasket is in tact as was the water passage o-ring. Alpha 1, 1984 M.Y. it seems the upper shift shaft seal is leaking. The shift shaft is grooved where the seal would ride so I'm replacing both the seal and shaft.

My question is this... is it reasonable to assume that back pressure and water flow from the exhaust is enough to fill the cavity in the bell housing and force it through the cable core? I have the exhaust tube not bellows so I'd have thought maybe not but it doesn't seem unreasonable to assume it could make it's way up the 14 inches of height or so to come out the cable end. It's in the shifter cavity so regardless of if it's the shaft or water tube o-ring, it's getting in there and I need to fix it.

I've pulled the cable core, blew it out and dried everything but I may replace the (new) cable out of precaution being I run in the salt...

Any other opinions on the matter are appreciated or if I'm missing anything. Thank you.

Sounds doubtful at best. I would be looking that the bellows are not leaking depending on position of the drive L/R & Up/Dn , or there is another leak in the cooling system

Have you looked at the driveshaft bellows closely ?

 

[Pmt133]

Sounds doubtful at best. I would be looking that the bellows are not leaking depending on position of the drive L/R & Up/Dn , or there is another leak in the cooling system

Have you looked at the driveshaft bellows closely ?

Drive bellows are dry. And new but I can check again more thoroughly when i get home from work... Only water was in the shift cavity between the gasket. I even wiped U-joint bellows out with a rag and they were bone dry/clean best as I could tell.

Boat off in water no drip. Boat running and moving in water drip from cable end onto valve cover from linkage. I didn't believwathat I was seeing if I'm being honest. How it made it's way up the cable makes no sense.

 

[kenny nunez]

When water collects in the shift slider area every time the drive is shifted to reverse the slider forces water through the cable. Pretty rare and keeping water out with worn parts it can happen. With the cable disconnected in the boat pull the slider back then put some heavy grease around the plastic tube then push the slider in all the way to force the grease inside the slider. Be sure the slider can travel both ways. The grease will displace the water.
Replacing the cable also is worth a shot.

 

[Bt Doctur]

mostly caused by a damaged water inlet O ring

 

[Pmt133]

Just for the heck of it, I went out to double check the o-ring. Maybe I should've stuck to grease like I normally use but I'm not seeing damage. I did find a thread a little while ago where Don said it had happened once or twice and it was the shift shaft bushing with exhaust gas. Maybe I am just that unlucky.

And regardless of that, this shift shaft was most likely leaking something as well just based on the pitting/grooves...

Regardless. It would appear these parts need to be replaced at a minimum anyway. When I'm off next I should have the new bits. I have a shaft in the miscellaneous mercruiser parts drawer but I seem to recall there being something wrong with that too.

New oring and clean up the sealing surface and grease it instead of a dab of bellows adhesive while installing!!! Live and learn.

 

[Candy Gramformongo]

I see a crack in the O-ring at about 4 o'clock in your photo.

 

[Pmt133]

I see a crack in the O-ring at about 4 o'clock in your photo.

The one following the curve from about 5-4? Bit of grease that just came off with my finger. Thought I found my smoking gun.

 

[Pmt133]

So I pulled the cable core blew it out with air and wiped it down with a clean rag. Put a small shot of 6-56 in there and blew that out and reassembled it. Cable is a brand new merc installed about a month ago. If I have any shifting issues I will be replacing it.

Next I pulled the old upper shift shaft bushings. The upper bushing/seal was pretty cooked to the point you could see light behind it with the shaft pressed in. So that probably wasn't helping. See below:

Finally, I found a small pit in the drive right near the water passage. I think the oring would compress enough to take care of it but to play it safe I installed it with a dab of permanent sealer. It's a rubbery setting oring safe adhesive I use at work. Dad said it kind of reminds him of type M.

So with those three things, hopefully i have it sorted out.

 

[Lou C]

Looks like you got the culprits! I have learned a lot about Merc drives reading these threads not having ever owned one. Only the OMC Cobra, which in terms of transom design is very similar to a Volvo SX (Volvo simply adapted OMC's transom design).

 

[Pmt133]

Looks like you got the culprits! I have learned a lot about Merc drives reading these threads not having ever owned one. Only the OMC Cobra, which in terms of transom design is very similar to a Volvo SX (Volvo simply adapted OMC's transom design).

I've worked on those helping dad over the years too. The only thing I hated was the god damn rubber ring you had to force the u-joint carrier through to get it on. Otherwise not a bad design... especially coming from the same company that thought the stringer was a good idea. I still have the shift alignment plate/tool for the cobra in the tool box as well as a couple other tools. Other than that they're all pretty much the same to work on transom to accessory drive.

 

[Lou C]

They actually improved that by making the bellows just a bit bigger, so I don't have an issue getting it on and have been doing all my outdrive maintenance for a long time now. Not sure but maybe the aftermarket bellows aren't made the same as OEM. Honestly, I have had very little trouble with the Cobra, all the repairs I have done were a few seals, the trim hoses, and just rebuilt the trim cylinders ($55 kit for each one, thank GOD the end cap came off lol).
One thing I can say is I have not had problems with thru the transom mount leaks and my boat has been in salt water, on a mooring, for our 6 month season for 20 years. However, you know how it is, no shops want to work on an OMC, my guy will but they are like owning a classic car, you have to find your guys to do stuff you can't.

 

[Pmt133]

They actually improved that by making the bellows just a bit bigger, so I don't have an issue getting it on and have been doing all my outdrive maintenance for a long time now. Not sure but maybe the aftermarket bellows aren't made the same as OEM. Honestly, I have had very little trouble with the Cobra, all the repairs I have done were a few seals, the trim hoses, and just rebuilt the trim cylinders ($55 kit for each one, thank GOD the end cap came off lol).
One thing I can say is I have not had problems with thru the transom mount leaks and my boat has been in salt water, on a mooring, for our 6 month season for 20 years. However, you know how it is, no shops want to work on an OMC, my guy will but they are like owning a classic car, you have to find your guys to do stuff you can't.

Yeah. Dad when to school for it when they first came out and it was an issue they brought up. But it was such a short window he serviced them I couldn't tell you. The one I did was a pain is all I can say. I'd work on them. He'd work on them but most younger guys have no desire lol.

 

[Pmt133]

So I test ran it and no leaks thus far. Going to launch it later and will report back.

The shift cable wasn't leaking on the trailer. I did however pull the water pump and re-seal it with a new pump to block gasket. Seems like the paper gasket Mercruiser supplied with the new pump is crap. It completely disintegrated on the starboard side and was mush on the port side. Light coating of indian head on the mating surface and my fingers are crossed. Cleaned the bilge too.

 

[Pmt133]

So the two others are now fixed..... But it seems I have developed a new leak now. I can't see it but have a drip on the transom plate. I am thinking y-pipe? Going to try and get my inspection camera back there to see what's what....

I really hope I don't have to pull the engine again. Not that it's hard but I was hoping rebuild whole boat and that's that. Never seems to be the case though.

 

[Lou C]

Sorry to hear that! And you've done a great job on this total refit of your family boat! But you'll get it I'm sure.
I thought if I ever wind up repowering this boat before I dropped the engine in, I had this crazy idea:
with the engine still out, install the outdrive.
make covers for the top of the Y pipe to prevent leaks
slowly back the boat in the water, so now you could see if there were any leaks! You wind up wasting an outdrive gasket but that's no big deal.
Crazy? Maybe not!
I have a complete like new from freshwater Cobra transom assembly and trim rams, hoses etc just sitting in my garage.
Anyway, I can see myself repowering this boat due to the work I put into it over the years but honestly if I was buying another boat it would have to be outboard powered. Just because of problems like that. I/Os have a lot of places to leak water.

 

[Pmt133]

Sorry to hear that! And you've done a great job on this total refit of your family boat! But you'll get it I'm sure.
I thought if I ever wind up repowering this boat before I dropped the engine in, I had this crazy idea:
with the engine still out, install the outdrive.
make covers for the top of the Y pipe to prevent leaks
slowly back the boat in the water, so now you could see if there were any leaks! You wind up wasting an outdrive gasket but that's no big deal.
Crazy? Maybe not!
I have a complete like new from freshwater Cobra transom assembly and trim rams, hoses etc just sitting in my garage.
Anyway, I can see myself repowering this boat due to the work I put into it over the years but honestly if I was buying another boat it would have to be outboard powered. Just because of problems like that. I/Os have a lot of places to leak water.

The problem is I did that. At the time it didn't leak so I'm at a loss what's going on right now.

 

[Scott06]

The problem is I did that. At the time it didn't leak so I'm at a loss what's going on right now.

Before u get too worried go through and tighten the hose clamps on the cooling water system quite possible one of them was not tight enough or loosened up with heat and cooling cycle

 

[Lou C]

It's not uncommon to have to retighten the band clamps for the elbows after a new installation.
When I converted my old OMC 4.3 from the OMC batwing exhaust to the later 2 piece style I spent the extra money for the Volvo OEM 90* exhaust down pipes vs the GLM copies just for that reason, to avoid leaks, and they have been leak free since installed in '17. I might have had to retighten one or 2 after the initial install. Hope your leak is easily resolved!