OMC Cobra Exhaust Manifold Question

[nutnboltguy]

HT32BSX115 Hi Rick, I realize this post (OMC Cobra 4.3L Exhaust Manifold Overheating) was 6 years old, but would like to work off some of the past info if possible... Are the manifolds in the above schematic the "bat wing" style?

I have these on a recently acquired 88 Reinell 173E with the 4.3l OMC Cobra... and I like the way they look and would hate to get rid of them...

I purchased the boat with the disclosed knowledge of an overheating problem and a seized motor... completely rebuilt the motor with a new block because the original was cracked and went through the outdrive to inspect and replace the seals in the water pickup tube and so on... upon inspection I found a lot of melted plastic which I'm guessing were the flaps you were referring to (#22)?

Anyhow, just fired it up yesterday afternoon and ran it for a good 15-20 minutes with the ear muffs on and all seems to be functioning fine.... looks like 160-170 degrees with tap water running through it?

Thanks.

 

[Scott Danforth]

You may like the way the batwings look, however when (not if) they fail and take out your motor, you will curse them

 

[HT32BSX115]

HT32BSX115 Hi Rick, I realize this post (OMC Cobra 4.3L Exhaust Manifold Overheating) was 6 years old, but would like to work off some of the past info if possible... Are the manifolds in the above schematic the "bat wing" style?

Howdy, Yeah. Don't answer old threads unless you started them yourself!

Batwings......Indeed they are and I agree with Bruce and Scott,

Those older style manifolds-risers ("batwings") were discontinued long ago. I don't think you can even buy them now (except for old used and new-old stock) In either case, you DO NOT want to use them. (new ones might be ok for a good long time in fresh water)

If your manifolds are even the least bit suspect (and if they're old and rusty) replace them with modern center-riser style new ones.

Regards,

Rick

 

[nutnboltguy]

No Title

funny, usually on other forums one would get chastised for not looking up threads pertaining to the topic at hand... and so i digress...

back to the bat wings - i ran my boat for the first time last monday, then tuesday and all last weekend. put about 6 hours on the new rebuild and she runs like a top... no overheating whatsoever... looks like 160 when im cruising at 2500rpm?

so anyway, my point is, i don't think this boat was ever run in saltwater and i know im never gonna run this boat in saltwater - ever. the boat had 600 hours on it when i got it and im pretty sure the previous owners ran it in fresh water (mountain lakes) ever since the boat was new...

so the question is - do i really need to worry about the bat wings letting me down? if so, whats a good replacement/upgrade?

 

[HT32BSX115]

funny, usually on other forums one would get chastised for not looking up threads pertaining to the topic at hand... and so i digress...

Ok, I am just posting a quote from up top of this page if you didn't see it......I am just going to suggest following the forum policies.

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[Emphasis mine]

There's absolutely no problem looking up and referencing old threads. In fact, it's encouraged. The problem comes when writing in them long ofter they're "dead" sometimes when the original poster ("OP") is long gone.....

It does however help YOU when you start a new thread and you "REF:" any old thread. We can all click on the reference and get a feel for what you're talking about if there's a question. posting a new thread gets it to the top and it's totally all about you and maximum visibility!

Now, "Batwings" They were discontinued for a reason. You're "rolling the dice" by using old ones.

There are enough people here who have ruined their engines when a manifold/riser leaked internally, and left them "winterized" with water sitting in cyls in SEP then didn't find out about it until JUNE when they decided to use their boat for the summer.

With separate manifold and risers, every 5 years or so, you can break them apart and inspect. fresh water manifolds and risers DO last longer when only operated in fresh water. BUT, they don't last indefinitely. I had to pull my former OMG 460 King Kobra apart because I had intermittent hydrolocking. (after shutdown, I had water leaking past riser gaskets into open exhaust valves)

Mine were only operated in fresh water from new. 1987 to 2005. There was still rust in both the risers and manifolds.

Granted, it didn't rust through..........it WAS a leaking gasket. Bat wings don't have gaskets. so for them to leak, they MUST rust through. (or crack from freezing etc)

After 30 years though, I would replace ANY manifold salt or no because you cannot see inside well enough to ensure that they'll NOT leak at some point.

Yes, I would replace those Batwings. There are plenty of kits out there (you can buy them right here on iBoats even) The 4.3L engine is so popular that there's a great many choices out there.

AND if I were replacing any engine with a new/rebuilt engine, I would replace 20+ year old manifolds and risers even if I thought they might still be usable.

 

[southkogs]

HT32BSX115 Thank you Rick.

 

[Scott Danforth]

batwings are like playing Russian roulette with your motor. its not if they will fail, it is when they will fail. thin castings with core shift issues

so the answer is yes, they will fail. it may be this week, it may be next week, it may be next year.

PS, thanks Rick

 

[nutnboltguy]

No Title

hey guys, i read up on the rules and guidelines and i get it and apologize for any inconvenience or confusion ive caused... didn't mean to ruffle any feathers and it makes sense how this forum works. thanks!

on a more forward note - what is a good replacement for the batwings on my OMC Cobra 4.3L? a link or picture please?

and again, im never (i repeat - "NEVER") going to run this thing in salt water - and for the 598 original hours this engine had on it im pretty darn sure it was never run in anything but mountain lake fresh water.

as you can see by the attached picture the engine seems to be running at 160 degrees at 2500rpm's.

thanks for your advice.

 

[HT32BSX115]

hey guys, i read up on the rules and guidelines and i get it and apologize for any inconvenience or confusion ive caused... didn't mean to ruffle any feathers and it makes sense how this forum works. thanks!

on a more forward note - what is a good replacement for the batwings on my OMC Cobra 4.3L? a link or picture please?

and again, im never (i repeat - "NEVER") going to run this thing in salt water - and for the 598 original hours this engine had on it im pretty darn sure it was never run in anything but mountain lake fresh water.

as you can see by the attached picture the engine seems to be running at 160 degrees at 2500rpm's.

thanks for your advice.

Without verifying your temp gage, 160 doesn't mean much. 160 is also ok by the way..... You can verify by using a Infrared temp gage (obtainable at Harbor Freight cheep!)

just point it directly at the thermostat housing and read the temp.

Manifolds can be obtained just about anywhere..... even here!

Here's a GOogle search suggestion. https://www.google.com/search?q=omc+...k1.WL3Jxcff4KU

 

[nutnboltguy]

thanks for that H232BSX115. and yeah, i need to have an infrared temp gage around the shop anyway.

my concern on a generic manifold is fitment. will it all line up with my exhaust fittings when it reaches the Y pipe or do i need to do a bunch of cutting and fitting? anyone have experience with this?

im capable of fabbing and fitting things up but im just trying to avoid a big project while im trying to eek out the last warm days of the year on the water....

thanks again

 

[HT32BSX115]

thanks for that H232BSX115. and yeah, i need to have an infrared temp gage around the shop anyway.

my concern on a generic manifold is fitment. will it all line up with my exhaust fittings when it reaches the Y pipe or do i need to do a bunch of cutting and fitting? anyone have experience with this?

im capable of fabbing and fitting things up but im just trying to avoid a big project while im trying to eek out the last warm days of the year on the water....

thanks again

Just about everyone with the Batwings swapped them for conventional center riser models. I think BARR indicates actual OMC part number compatibility.

If your engine is an 88 OMC 4.3L, the manifold is OMC 984222 If you do a search, you'll find BARR and GLM. Go to TC Electronics/Marine site for all the part numbers.

GOogle "51472 GLM" it'll be about halfway down the page.

 

[Lou C]

The manifolds and risers will fit fine, what the kits give you are the correct 90* elbows that adapt from the 4" riser outlet to the 3.5" OMC Ypipe. I'd use Barr if you can get em vs GLM. If you get stuck having to use GLM Id make sure to check the sealing surfaces for flatness with a straight edge & feeler gauges. If they are not flat within .002-.003" Id take em to a machine shop and get the sealing surfaces of both the mani and riser re surfaced....should not have to do that but that is the price of made in C***a

 

[nutnboltguy]

excellent! thanks to both of you for the part numbers and the difference of brand quality.

one thing i dont like about the batwings is they are in such a weird place that it makes it extremely difficult to get in to the top of the heads to double check and adjust the valves - which i intend to do shortly. 10 hours on the new rebuild.

 

[Lou C]

I just upgraded my motor from the Batwings to the Volvo style center riser manifolds & risers using Barr manifolds & risers. I used the Volvo OE 90* exhaust pipes that adapt the 4" riser to the 3.5" Y pipe. The combination of the Barr risers and manifolds and the Volvo hoses and exhaust pipes (I did not want to use the GLM stuff) fits the old Cobra Y pipe perfectly. The Volvo 90* exhaust pipes are pricey but its a one time expense.

​BTW, while my Batwings passed the acetone test (fill with acetone and check for leaks in the exhaust ports), what I noticed was this, if you look up in the exhaust opening inside you can see flaking rust. I was concerned that there were more areas of rust that I could not see, and this could loosen and fall into a cylinder via an open exhaust valve. As a test, I tried tapping the manifold with a small hammer lightly and sure enough, rust flakes appeared in the exhaust ports.

https://www.dropbox.com/s/55j6h4dd1u8fv0k/IMG_2273.MOV?dl=0

​Here's a short vid of the engine running with the center riser exhaust after the top end rebuild (blew both head gaskets end of last season), took it all apart over the winter and installed a pair of re-man marine heads, and Fel Pro marine gaskets. The old Batwings were 6 seasons old and here in salt water that's about all you get, safely.....

 

[Lou C]

No Title

Here's a pic fitting it all together....

 

[bruceb58]

Your engine looks clean for a saltwater boat.

 

[Lou C]

Thanks Bruce, I painted the valve covers, intake manifold, thermo housing, and the re-man cyl heads before putting it all together. You can still get the original OMC Charcoal paint in spray cans. The manifolds came painted so Ieft them Barr Black.....
​Corrosion control is a constant battle in salt water, this boat has had 15 seasons on the mooring for 6 months out of the year, this was the first summer since 2006 (that year I did the deck, interior etc) that it was not on the mooring.

 

[bruceb58]

My boat has spent time in salt water but will likely be spending most of the rest of its life in fresh. Fluid Film thanks to Bondo recommendation helps a lot with the corrosion I get from water landing on the engine and sitting. Mine does not look like yours though.

 

[Bondo]

Fluid Film thanks to Bondo recommendation helps a lot with the corrosion I get from water landing on the engine and sitting.

Ayuh,.... Neat stuff, eh,..??

My local Napa started stockin' it, so I don't have to buy it mail order by the case anymore,....

I even saw a 5 gallon bucket of it hidin' in the corner the other day,...
Would be perfect for undercoatin' a vehicle before winter,....

 

[shaw520]

I started under coating my truck with it 2 yrs ago,.a remarkable difference.