OMC Stringer Exhaust Leak

[HookEm17340]

I hope someone can shed some light on this for me. I have a 1985 OMC 3.0. I need to replace the impeller. I plan on replacing the impeller housing as well. I have an exhaust leak coming from the access hole for greasing the swivel bearing that I'll be repairing as well. Does anyone have an idea where the exhaust may be leaking from? I see a seal where the upper and lower gear cases meet that looks like it's not sealing. If it's a seal, does anyone know if the seal is available by itself or do I need to get a seal kit.I replaced the exhaust seal where it meets the transom last season and it's working well. Any thoughts or advice is most appreciated.

Thanks!

 

[flockshot]

Re: OMC Stringer Exhaust Leak

I just replaced my 83 400 stringer impeller and housing, along with a upper unit seal kit. When you get in there you may decide, like I did, that many of those exhaust leaks are by design, or at least no big deal. Make sure that your water pump can not suck in exhaust though. That big seal you are refering to is not part of the upper unit seal kit and I do not believe that it really seals anything. It looks to me like water entering the unit at that point will be pushed out the prop by the exhaust.
I did that job with the Seloc and Climers manuals but now I have the OMC Service Manual which, i believe, answers questions better.

 

[HookEm17340]

Re: OMC Stringer Exhaust Leak

When I have it running on the muffs and i poke at the large seal between the upper and lower gearcase, water and exhaust come out. I have almost as much water coming out of the hole shown in the pic as I have coming out through the prop. How is the exhaust intended to get from the manifold to the prop?

Thanks.

Thanks to floattest for the pic. I borrowed it from his impeller replacement post.

 

[flockshot]

Re: OMC Stringer Exhaust Leak

The pasage for exhaust to the prop is behind the water intake area of the lower unit. It seems that OMC used the area they needed for the water pump and drive shaft and just left the rest of the cavity open for exhaust gas and water.

 

[superbenk]

Re: OMC Stringer Exhaust Leak

You might want to check your swivel bearing seals. Mine was all chewed up from the upper gear case being inserted into the lower case incorrectly. I replaced the upper swivel seal when I did the impeller. I didn't bother with the lower at the time because I didn't want to rip apart the lower case to get at the swivel bearing housing.

Pics of my impeller job if it helps: http://picasaweb.google.com/superbenk/ImpellerReplacement

 

[HookEm17340]

Re: OMC Stringer Exhaust Leak

Thanks for the pics superbenk. I'm assuming that you had a similar exhaust leak and replacing the upper swivel bearing seal helped.

 

[superbenk]

Re: OMC Stringer Exhaust Leak

Thanks for the pics superbenk. I'm assuming that you had a similar exhaust leak and replacing the upper swivel bearing seal helped.

Honestly, I didn't notice the leak, but I didn't pay much attention. Though when I had it apart & read about it, it got me thinking about leaks and inspired me to fix that seal.

 

[wire2]

Re: OMC Stringer Exhaust Leak

I remember that hole in my former '84 800 stringer. I'm 99% certain it's there to relieve exhaust pressure when not on plane. To force the exhaust all the way down to the prop makes for hard starting.

The forward motion of the boat on plane creates a a vacuum behind the flare of the prop, which sucks the exhaust out. At speed, the relief ports do nothing.

 

[superbenk]

Re: OMC Stringer Exhaust Leak

I agree with wire... if you look at where the hole is, there is nothing closing off the exhaust cavity from the hole in the housing. Any exhaust traveling through the housing would exit through that hole naturally by design.

 

[HookEm17340]

Re: OMC Stringer Exhaust Leak

I believe I remember hearing that a bad swivel bearing seal can cause the leak. Someone suggested pumping it full of grease for a temporary fix. In the attached picture just above the prop is the idle exhaust relief holes. I'll be tearing it down next Saturday and see what's really going on there. Thanks all for your advice.

 

[HookEm17340]

Re: OMC Stringer Exhaust Leak

We tore it down today. It was quite a battle to get things apart. For this boat spending most of it's life in freshwater, there appears to be some serious lack of maintenance. After getting the impeller and housing out, I first noticed that the impeller was still quite pliable, but showed signs of wear. The impeller housing...wow...was terribly pitted inside and a piece of if was broken. It made superbenk's housing look like a brand new part. I suspect that the impeller has been replaced at one time. The impeller plate showed no signs of ever having any sealant put on it. The carbon deposits were a clear indication that exhaust was entering the pump. The large o-ring seal that goes between the pieces that encase the impeller housing was stretched and not even sealing it. The swivel bearing seal is toast. I'm gonna have to order some parts to put things back together. It is true, the hole to access the zerk fitting for the swivel bearing is completely open to exhaust. I'll try to take some pics of the impeller housing tomorrow...it's unbelievable nasty. I'll have to include some pics of the topside of the boat....they don't match at all. I guess the previous owners were more wash and wax than oil and grease. What a shame....such a nice boat.

Thanks again for all the input!

I gotta get back out there...crabs are starting to come in good.

 

[Howard Sterndrive]

Re: OMC Stringer Exhaust Leak

a piece of if was broken.

that's common

it's from ice - all it takes is leaving the drive tilted up through the winter with the prop uncovered

 

[HookEm17340]

Re: OMC Stringer Exhaust Leak

It appears that replacing the impeller & housing was the easy part. I'm having a heck of a time finding the swivel bearing seals. I'm wondering, are they included in a lower gearcase seal kit? Do I have to buy a new swivel bearing to get the seals? I haven't been able to find any place that sells just the seal. Can someone point me in the right direction?

Thanks alot!

 

[superbenk]

Re: OMC Stringer Exhaust Leak

It appears that replacing the impeller & housing was the easy part. I'm having a heck of a time finding the swivel bearing seals. I'm wondering, are they included in a lower gearcase seal kit? Do I have to buy a new swivel bearing to get the seals? I haven't been able to find any place that sells just the seal. Can someone point me in the right direction?

Thanks alot!

I got my swivel bearing seals in the lower gearcase seal kit. It's a shame because I didn't need to/want to tear apart the lower case (I didn't) so I ended up with a bag full of seals, bolts & gaskets I may never use just so I could replace one seal. Oh well, spare rubber, I guess.

Btw, I'm not sure my impeller really needed replacing after I got into it. It didn't seem all that bad next to the new one, so it may have been done a lot more recently than I imagined. I put the new stuff in anyhow since I had it all apart & had the new bits anyhow.

 

[HookEm17340]

Re: OMC Stringer Exhaust Leak

I've attached a few pics of the old impeller & housing. The impeller didn't have a bad set and was still quite pliable, but was definitely worn. The top of the impeller housing was warped on the top side as well. Another thiing that I forgot to mention is that the large o-ring that seals the two halves that cover the impeller housing was on the outside and not held in the groove that the two halves make. Like I said, more wash & wax than oil & grease. I'll follow up with some pics of the swivel bearing seal operation next weekend. Hopefully it will help someone in the future.

 

[HookEm17340]

Re: OMC Stringer Exhaust Leak

This weekend I tackled the swivel bearing seals. The uppermost one was shot and the two lower ones appeared to be working but may have been near the end. I replaced the clogged up exhaust riser and checked the end plates and manifold. After getting the lower unit installed, I put it on the muffs and fired it up. The first thing I noticed was that there was less water coming from the impeller housing area and a heck of alot more water coming through the prop. I ran it at about 1500 rpms, watched the temp go up just above 175, then drop back just below 175. Looks like the thermostat is working. I increased the rpms a bit and the temp stayed right around 175-180. When i brought it down to idle and looked out back, there was some steam coming from the prop. It was about 80 deg outside. Does this seem normal? I figured that the engine would run a bit cooler being raw water cooled. I'm a little worried that I have a headgasket issue.

Thanks.

 

[superbenk]

Re: OMC Stringer Exhaust Leak

I increased the rpms a bit and the temp stayed right around 175-180. When i brought it down to idle and looked out back, there was some steam coming from the prop. It was about 80 deg outside. Does this seem normal? I figured that the engine would run a bit cooler being raw water cooled. I'm a little worried that I have a headgasket issue.

I dunno, 175-180 sounds like steaming water to me. 212F is boiling, I wouldn't want to stick my hand in 175F & a hot tub/bath is ~105F

 

[wire2]

Re: OMC Stringer Exhaust Leak

The cooling water coming through the drive is not all at the same temperature. Most is ~175?, some is less, some is more. The "more" makes steam. It's normal.