OMC Exhaust Manifolds??

[Shredhead]

Anyone know when manifolds should be changed? I got a Four Winns(89) with OMC 4.3l, not sure of engine hours but boat has been well maintained and is in immaculate condition. I also know it is hard to find manifolds for this engine and they are not cheap. If anyone had a set for sale reasonably priced I may be interested.
Thanks

 

[Coors]

Re: OMC Exhaust Manifolds??

2 years for salt, 5-6 for fresh. Pull the risers and check them- don has a pinned, in search ,with pictures.

 

[Gary H NC]

Re: OMC Exhaust Manifolds??

I had seen a set of used ones on ebay go for about 300 a few weeks ago. I would not buy used.They may look fine on the outside but who knows how thin they are inside.
If you have the original 89 models my guess is they are near needing replaced.
I'm needing to replace mine also.
The cheapest i can find is ebasicpower. Still looking at a grand....I know it sucks....

 

[Shredhead]

Re: OMC Exhaust Manifolds??

2 years for salt, 5-6 for fresh. Pull the risers and check them- don has a pinned, in search ,with pictures.

Hey, dont mean to soound stupid, but I am new to this forum type stuff and am unsure what "pinned, in search, with pictures" means. Thanks yet again for your help!!!

 

[Gary H NC]

Re: OMC Exhaust Manifolds??

No risers to pull on these Coors,They are all one piece.
Thats why the after market replacements are a fortune.
Oscoe and GLM are the only replacements out there..

 

[Gary H NC]

Re: OMC Exhaust Manifolds??

Forgot to mention,Welcome aboard Shredhead!

 

[Shredhead]

Re: OMC Exhaust Manifolds??

Hey thanks a million, and thanks to everyones advice and suggestions, its greatly appreciated!!!

 

[tampc]

Re: OMC Exhaust Manifolds??

May I ask why have to replace after 5-6 years in fresh water?
My is in the same year '89 and it has crack due to wheather *ICE* and FIX it with BJ weld and it work wery well about 2 year now.
And yes it is very costly

 

[Lou C]

Re: OMC Exhaust Manifolds??

If that crack lets water drain into a cylinder it's going to cost more than the cost of manifolds to replace the engine.
There are 2 places that I have heard of selling a conversion kit to convert the OMC one piece to a 2 piece set up. One is Sea Way Marine in Washington State and the other is ebasicpower.com. Either way you are going to have to spend about 800 in parts for the conversion, then after that the cost to do the manifolds will be the normal price since you only need to buy the additional hoses and hardware once.
I have the one piece on mine too, I replaced the OE in 2004, and those only have 2 seasons on them, when I saw the price starting to go up I got a spare set.
The life of ex manifolds is hard to predict, you have to take em off and inspect, and try to replace well before you get water in a cylinder.

 

[Gary H NC]

Re: OMC Exhaust Manifolds??

I did some adding and checking.converting to the Volvo SX style will run about 900 bucks with all the elbows and hoses.Or you can get the direct fit replacements from ebasic for 995....
If i go Volvo re-fit the next time i replace will cost me about 500..
Either way thats a big hit to the wallet!:%

 

[gkosel]

Re: OMC Exhaust Manifolds??

I have a 91 4.3L OMC and have small crack in one of my exhaust manifolds too.

I noticed this the last time I had it out prior to getting it winterized.

The marine repair place that I get most of my work done at, said that they should be able to put a cold pack weld (or something like that - it has been several months since they told me this) that would take care of the problem.

I was about to say that I have looked at the GLM replacements for my motor and have not found them to be nearly as expensive as I have seen posted on this board, until I realized that I do not have the one piece sets that are more expensive.

Is it worth it to fix with the weld and keep an eye on it, or am I playing with danger?

If I do replace, is it best to replace both sides at the same time?

How hard is it to replace these manifolds? Is it something that someone not a whole lot of experience could do?

Thanks

 

[Gary H NC]

Re: OMC Exhaust Manifolds??

That 91 model 4.3 with a 2 piece.Yes,replace them before you ruin the engine.I would replace both sides that way you know your good for awhile.

They are not hard to replace,a few bolts and hose clamps.Clean up the mating surface on the head and put the new gaskets on.Bolt everything back up,good to go.Unless you break a bolt off...

 

[gkosel]

Re: OMC Exhaust Manifolds??

That is what I was afraid of hearing. I am not looking forward to spending the bucks to put these on this year. But, I guess this is nothing compared to blowing an engine.

I am assuming that while doing this I should also replace the risers in addition to the manifolds?

Is there anything else that I need to purchase other than what is included in the eBasics kit that you have referred to in another post?

http://bpi.ebasicpower.com/mm5/merchant.mvc?Screen=PROD&Store_Code=ebasicpower&Product_Code=BPIV6VOL

Thanks for the help.

 

[Coors]

Re: OMC Exhaust Manifolds??

the exhaust is the weak point; I had a new engine installed by a shade-tree. He used rtv between the manifolds and the risers. I sucked water into #7 cylinder, but pumped it out before damage resulted. Then I stayed on this forum and read every old post, and bought a factory manual. Doing the same will save you big bucks. welcome aboard.

 

[Gary H NC]

Re: OMC Exhaust Manifolds??

gkosel, do you have the one piece manifolds on it now?

That link you have is the newer style and you will also have to buy the exhaust turn down tubes and rubber hoses to convert it to volvo manifolds.Also do have the room for that in the engine compartment?
Read Don's advice in this thread,

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=24;gtid=1266050

 

[KaGee]

Re: OMC Exhaust Manifolds??

2 years for salt, 5-6 for fresh. Pull the risers and check them- don has a pinned, in search ,with pictures.

Only 2 years in salt? I suppose if you never ever flushed them.

Hey Shred, your question is subjective to a lot of variables. Up here in Ohio, more manifolds probably get replaced due to freezing than rust out. Not uncommon to hear of guys getting 12-15 years out of a properly maintained set.

 

[gkosel]

Re: OMC Exhaust Manifolds??

Thanks for the reply Gary. I have been keeping an eye on that thread too. That is where I found the link to the eBasic Manifolds.

I do already have the two piece manifolds just as in the picture. So I am assuming that I should be able to get the kit that I had referenced earlier and that should include everything I need right?

Kagee, I noticed that your manifolds were painted blue to match the rest of the engine. Did you paint them, or did they come that way.

It would be nice to get the new manifolds in the OMC gray or whatever color that is supposed to be to match the rest of the engine.

Can you tell what shape the manifolds are in by pulling them off and inspecting? I can see how some people in the midwest that can only use their boats for 3-4 months out of the year can get 10+ years out of their manifolds.

But how can you tell how long you can safely push them?

 

[Gary H NC]

Re: OMC Exhaust Manifolds??

The kits from ebasic come with all the gaskets and should be everything you need.

Don had posted in another thread this pic,

It gives you an idea what to look for..

 

[KaGee]

Re: OMC Exhaust Manifolds??

Kagee, I noticed that your manifolds were painted blue to match the rest of the engine. Did you paint them, or did they come that way.

It would be nice to get the new manifolds in the OMC gray or whatever color that is supposed to be to match the rest of the engine.

Can you tell what shape the manifolds are in by pulling them off and inspecting? I can see how some people in the midwest that can only use their boats for 3-4 months out of the year can get 10+ years out of their manifolds.

But how can you tell how long you can safely push them?

The manifolds were painted by me. They came with a basic black primer coat.

As for how long? That's subjective. Pulling them for inspection, looking for signs of excessive flaking. The age of them. Any sign of the engine stumbling at idle. Inspection of the spark plugs... a super clean looking spark plug is a sure sign that water is getting in.

When a manifold goes, it may trickle water into the cylinders or it can let go totally, flooding the cylinder(s) causing a hydro-lock condition. You don't want that.

If you are to the point where you are thinking about them, it's probably time to consider replacement.