OMC 5.0 riser dripping water

[peanutbay1]

O.K. guys after all the work I did to get my engine running correctly we have discovered a small drip coming out of the starboard riser on my 5.0 OMC. My full intention is to pull the riser and see if I can regasket or if needed I will replace the riser and/or manifold. My engine is very clean for its age and has little rust anywhere. I am headed to raystown for the holiday weekend and I have been seeing posts here and there where people got water in their oil and caused damage. I am dripping at a single stud on the riser,my oil is checked each day that I go out to boat. Should I be worried for the weekend???? I would pull the riser before friday but I know how things go and I could see a bolt breaking or something of that nature happening. I am just looking for some honest input. Thanks!!!

 

[Bondo]

Re: OMC 5.0 riser dripping water

Ayuh,... If it's Leaking Internally as well as externally,...
You're risking Hydro-lock more so than just alittle water in the oil...

It's Your gig,... Roll the Dice if you want,.... I wouldn't....

 

[peanutbay1]

Re: OMC 5.0 riser dripping water

I am going to get the gasket today. Is there any tips to helping with the bolts coming loose without breaking. I dont think I can get penetrating oil down to the threads as long as the bolts are. Would mild heat (propane torch) on the manifold help? I am assuming that it could be that the mating surfaces are damaged or a failed gasket.What is the usual problem??? The riser leak is new and there is little rust on the manifold. Should I expect to put new bolts in as well??

 

[HT32BSX115]

Re: OMC 5.0 riser dripping water

If you can actually see the water leaking from the riser gasket area then it's probably a gasket. If it's dripping from the bottom of the exhaust manifold you may have a crack (from ice) in the bottom of the manifold. Sometimes you don't get all the water out of them and it pools in the bottom of the manifold.

When you get them apart, if the sealing surfaces are not really nice and clean, you probably should replace both manifolds and risers.

When did you last remove and inspect the riser/manifold sealing surfaces?
(removing them and replacing the gaskets and using thread lubricant prevents sticking bolts when you next remove/inspect/replace riser gaskets)

If those bolts are rusted so badly that they break, you may have to just replace everything anyway. (is this a salt-water boat?)

Ayuh,... If it's Leaking Internally as well as externally,...
You're risking Hydro-lock more so than just alittle water in the oil...

This is exactly why I pulled the manifolds and risers on my former High Tech OMC King Kobra 460 engine. I had leaking riser gaskets on BOTH SIDES that allowed water to leak back into open exhaust valves........No problem (I said!.....) I'll just replace both the manifolds and risers!!!

Dealer said: Sorry Charly! Those are NOT available anymore

So I fixed it a different way.


Cheers,

Rick

 

[peanutbay1]

Re: OMC 5.0 riser dripping water

My riser is actually leaking out of the top of the riser at one of the threaded holes (at the hex),not at the gasket surfaces. There are no signs of leaking anywhere else. As for the boat history,I have owned it 2 seasons and never had the risers and manifolds apart. The previous owner ran all central PA freshwater. The motor does not have hardly any rust on it. I wish I could wait until after my weekend trip to adress this but after reading some of the posts on this subject I have become nervous. I am very fussy about my boat and it has been a long 2 year process to get the boat as nice as it is and I would hate to damage the engine for a $10 gasket.

 

[HT32BSX115]

Re: OMC 5.0 riser dripping water

It's a REALLY good idea to pull the risers every few years and replace the gaskets (of course, you destroy them getting them apart).


This gives you the opportunity to inspect the sealing surfaces and look at the thickness there.

The cast iron manifolds and risers slough-off metal in the form of rust inside all the time. They have a finite life and get thinner and thinner until they (if ran long enough) actually break thru. Then you have raw water in the exhaust.

When you shut it down that water runs back into open (hot) exhaust valves possibly warping them and sitting on top of the piston(s) and causing a hydrolock when you try to start it later.

(you'll initially think you either have a dead battery or a defective starter.....that's what I thought.)

It's usually not enough water to get into the oil.......and what little does, evaporates if you run the engine a lot later.

In mine, it was obvious that water sat on top pf a couple of pistons all winter since it happened every time I shut it down.

 

[peanutbay1]

Re: OMC 5.0 riser dripping water

RISER LEAK UPDATE:

I found the leak on my riser to be a small crack at the pad where the bolt passes through the riser into the manifold. I am ordering a new riser this morning. It looks like 3 of the 4 bolts will come out fairly easy. The crack should just be from the water jacket outward so I dont think we had any internal leaking but I want to be safe and replace the riser anyway. I am sure the one bolt is going to break off. On my jetskis this happens alot with our aftermarket exhaust systems and we just drill/retap or helicoil them. Can I assume I can do the same thing to this manifold??? Is the tapped hole in the manifold blind or thru???

 

[HT32BSX115]

Re: OMC 5.0 riser dripping water

Well,

That's up to you. If they're otherwise in good condx, you might be able to drill/tap the holes.....

When risers and manifolds get "bad", most people just replace them since it's very difficult to determine when they'll fail. Depending on whether you're operating in salt or fresh water you're looking at 5-7 years in salt and maybe 10-15 or more in fresh. (your mileage may vary)

If you're up against the limits and you have a really good engine it's just not worth the risk since an engine sitting for just a week with salt water in the cyls will usually result in a complete rebuild or replacement.


Let your conscience be your guide.......



Regards,


Rick

 

[peanutbay1]

Re: OMC 5.0 riser dripping water

O.K I am confused... If I found a small crack in the elbow only and the manifold is clean with no rust why would I change the manifold. It looks like the bolt to the elbow had a dialectric condition that caused the bolt to corrode which in turn caused a rust build up at that SINGLE HOLE and put pressure on the casting foot and caused it to crack. This boat is an "88" and the risers/manifold could be original but everything looks clean. I was just trying to find out if the tapped holes in the manifold are blind or thru in application.

 

[Bondo]

Re: OMC 5.0 riser dripping water

I was just trying to find out if the tapped holes in the manifold are blind or thru in application.

Ayuh,... I donno,... But you will as soon as you pull the riser...

If that's been in Sweetwater it's whole life,... The Rotten manifolds should be a Non-issue...
Their Good for 40 or 50 Years in Sweetwater....
Matter of fact,... Freezing is about the Only reason for replacing 'em around here...