Exhaust Manifold?

sturgeon1 · 01-25-2004, 02:30 PM

I have a 120h.p. 4 cylnder omc. The square part of the manifold that the water runs through has about a 4 inch crack in it. My ? is does anyone know if There is any tubes of stuff I can put on the crack without taking it off the motor, something like JB weld or something. Thanks for your help, sturgeon1.

Green Machine · 01-25-2004, 03:04 PM

Tough call.

With out taking it off, you will have to make sure it is very clean and dry for the JB to work. It is not that hard to take the manifolds off, unless your motor is "shoe-horned" in. I would take them off...........then weld the crack and also look for more cracks......you might be surprised. If then, cheaper to go replacement. Is this a result of the cold weather?? LOL

Green Machine

sturgeon1 · 01-25-2004, 06:34 PM

Hey there GREEN, the crack is in the square part below the carb where the water flows through about 4x4 square. yep caused by cold weather. So you think JB weld might work because it doesnt get hot. What could I use to clean the area with? Thanks,sturgeon1.

sturgeon1 · 01-25-2004, 06:36 PM

TTT please, thanks, sturgeon1.

Green Machine · 01-25-2004, 08:26 PM

I was thinking if it was caused by the cold weather (freezing), you may have more damage than you can see from the outside. The JB may fix the 4" crack, but could be pointless if there are more cracks. For it to work, sand or better yet, use a dremel tool to reem out the crack and give the JB something bond to. Sort of like welding, make a groove and then fill it. Then clean it with acetone or something to remove the impurities. Buy the slow cure JB, the fast cure is not as strong, and apply it and let dry and harden for atleast a couple days, preferrably with a some heat. The stuff is strong if done right. It is heat resistant and fuel resistant too. Good luck!!!

Green Machine

Green Machine · 01-25-2004, 08:30 PM

Just got to thinking........you said below carb....that must be your intake manifold, not the exhaust manifold. If that is cracked from freezing, not to scare you, but I would have to guess more damage inside. Hopefully not. :depressed:

Green Machine

YaHoeeFishOn · 01-26-2004, 10:51 AM

Hello , My first boat was a 1972 Larson with a 153CI 120HP OMC. It was my farthers boat before me. My dad hadn't winterized boat and water froze in manifold. The 4 cyl Chev is both the exhaust and intach manifolds in a single manifold. Mine had cracked from just the water jacket to outside, it had not cracked into the intach or ehaust runners. I tried using a sealant to stop leak. It failed and cracks spread further down edge bottom manifold. My neighbor said small radius holes would have to be drilled at end cracks to stop them from spreading and then take it to a head welder to have cracks welded. The heat/cooling expansion cycle will just stress cracks worse. I gave up next season and boght a replacement when I was in Columbia after launching at Sundial and manifold split all way to back. No one made a OMC aftermarket at that time 1982. So I had Rays boat yard order me a replacement and I bolted in a replacement. 2 years later on lake Merwin and the thermastat neck of front of the engine broke. I think it was damaged from freeze as well . Anyways I think do to expansion and thermal stress you should spend 300 $ ? bucks OEM or maybe now a aftermarket manifold. It was a expensive leason , remember to drain those petocks before Thanksgiving .

01-26-2004, 12:00 PM

Don't use JB Weld. Have it brazed or replace it.

CATCH AND EAT · 01-26-2004, 12:04 PM

Why risk your life and the life of others to JB weld? You could get yourself in serious trouble should that stuff fail. Take it off and fix it right my friend. If it is the intake manifold you better for sure take it off. Bet there is a bigger mess to clean up than just a manifold. :depressed:

riverhawk · 01-26-2004, 04:14 PM

Regarding the 120 when you find out all the damaged parts I have some heads and manifold but check for a crack right below the manifold in the cam shaft boss area hope not. But thats where they crack out good luck

sturgeon1 · 01-26-2004, 04:53 PM

HEY there RIVERHAWK, Its cracked at the bottom of the 4x4 tube that has the 2 square end caps, one of the end caps have 2 small hoses coming off the front of it. Water flows through this thing.Thanks,sturgeon1.

Fishybill · 01-26-2004, 06:12 PM

Surg,

Unless I am mistaken, that manifold is steel. This means it is probably weldable. However, usually when a manifold cracks, advanced water jacket erosion (or an overheat) is the reaon. You could probably strip and weld the crack, but I doubt it would hold for long even if the crack is accessable to be welded from the inside of the manifold as well as the outside.

You could replace the manifold with a spendy new part, or replace it with a slightly less spendy used part. But don't expect anything less to work any better or longer than a butterfly bandage on a tire puncture. Consider the age and relative water jacket erosion factor of your engine, then decide on the new or used replacement manifold. I hope that helps.

YaHoeeFishOn · 01-29-2004, 12:44 PM

Its cast iron. Yes it can be welded . But only it hasn't cracked into the exhaust or intake runners. I tried patching mine but the cracks just kept spreading. Unlike a car . You cant just park it and walk home . I hope your outdrive and other parts survived freeze , The head and block have frost plugs . the thermast mount and manifolds don't .

Thumb Burner · 03-14-2004, 10:29 PM

I sure wish I would have read this post before I bought this boat today. I am going to have to take a look and see how this problem was solved.
hmm
[img]graemlins/1zhelp.gif[/img]

crabbait · 03-14-2004, 11:18 PM

It may be too late for you Scout, but for others it is a really good idea to have a Marine Survey performed before buying any used boat. The cost is generally $10-15 per foot of boat length. Engine surveys are an additional charge.

The cost of the survey can usually be bargained into the purchase price. If the survey reveals problems (water soaked transom or rotting wooden stringers in a glass boat, cracked aluminum hulls, cracked exhaust manifolds or poor compression in a cylinder or two) you can decide whether the problems are a deal breaker or negotiate the cost of repairs.

In any event, a survey can go a long way toward aleviating buyers remorse and keeping you from buying someone elses boat problem.

Thumb Burner · 03-15-2004, 08:24 AM

Looks like it was a JB Weld job to me. I know nothing about boat engines. Anyone know where a good place to get parts for this. I need to look at the engine again and see what make it is and call around to see where I can get a manifold. I want it fixed right. I wont do the engine work myself, lucky I have a father-in-law who is a mechanic and has a shop.

I am not going to turn this into a nasty post. I figure it was my fault for not having it looked at when buying the boat.
Lesson Learned.
This boat is going to be a project boat for me, I would like to restore it probably next winter.
Well any help on where to get parts?

SS

YaHoeeFishOn · 03-15-2004, 10:48 AM

I got mine from rays , old man ray is no longer alive. At that time no one made afternarkets for a omc 4 cyl. He ordered it and I went to the marine warhouse and picked it up. They wouldn't sell to public. He was still cheaper than Staff's or Harveys. I think I payed 260 to ray , invoice was 220 , other boat yards wanted 300.

[ 03-15-2004, 01:00 PM: Message edited by: YaHoeeFishOn ]

Pilar · 03-15-2004, 12:22 PM

Sturgeon1, manifolds only last 3 to 5 years and less if they get salted and not flushed or zincs are not replaced religiously. You can get a new manifold from Seaway Marine in Seattle for $350, complete. They may also have new old stock (N.O.S., new original in the box for 20 years) for less than that. They buy marinas out when they go out of business and the N.O.S. stock they have is amazing.

I hated spending that much on my motor but the old manifold was severely corroded and it was time. How many times can you goop on the RTV before you get sick of messing with it? The good news is that I got enough of a horsepower boost from the the new Barrett manifold to up my prop pitch one notch from 19 to 21. Top speed is up by about 10% and so is fuel economy.

You can't go wrong with new.

If you cob the old one back together and the engine overheats, you may spend $2000 instead of $350. Overheat is the #2 killer of I/O power plants.

Also if the manifold cracked you must be diligent and pressure check the water jackets on the motor. The motor may be cracked or a freeze plug pushed out. Freeze up is the #1 killer of I/O power plants. Freshwater cooling (heat exchanger) on an I/O completely prevents this problem. ANy new I/O motor should be equipped with freshwater cooling, it doubles the life of the motor.

YaHoeeFishOn · 03-15-2004, 12:27 PM

I just searched the osco and barr web sites. looks like they still don't make that manifold aftermarket . I not sure about that 3-5yrs mtbf. Yes they scale up, need to make sure slits in elbo's are open. A old oil dip stick in a drill scapes them out, or soaking in a demineralizer. read your manuals.

[ 03-15-2004, 01:35 PM: Message edited by: YaHoeeFishOn ]

TonTo · 03-15-2004, 01:04 PM

I have the same problem....no solutions for ya just alittle understanding :smile: darm OMCs the one I'm running now has been brazed by the previous owner...and it still drips into my bilge,but I can pump it from time to time,I have another but it's got JB weld gooped all over it,I've chipped some out of the way to ***** how much damage it has to it,I would suggest the braze for a cheap fix.But with the other(my spare) is there a welder out there anyone might recomend,it is cast,and I'm not ready to try welding cast myself,I would like to get a leak proof manifold if I can without spending the $289 for a new one.I probably will end up buying one soon but hey what can I say I'm cheap.