4.3L OMC COBRA WATER IN CYLINDERS

[WZNYROBO]

I HAVE (HAD)A PERFECT RUNNING 1987, 4.3L OMC COBRA ON A 19FT CELEB. (TOTAL HOURS 270) AT THE BEGINING OF THE SEASON I "TULIPED" A VALVE. PULLED THE HEADS OFF, HAD THEM FIXED AND RE-ASSEMBLED. TOOK A DOZEN OR MORE TRIPS SINCE THEN, ONLY NOTICED OIL LEVEL RISING (NO SIGNS OF WATER ON DIP STICK)<br />JUST OVERHEATED AT THE END OF LAST TRIP (74 MILES)<br />SHUT DOWN MOTOR AND TOWED BACK. HYDO LOCKED, WATER IN ALL (ALL) CYLINDERS. BLEW OUT WATER, COMPRESSION CHECK ALL CYLINDERS GOOD. FOGGED MOTOR, RUNS FINE WITH GARDEN HOSE. NO OVERHEAT. CHANGED OIL (APPROX 2 QTS WATER CAME OUT). REMOVED EXAUST MANIFOLDS (20 YRS OLD) DON'T KNOW WHAT TO LOOK FOR, WATER IS PRESENT, NO SIGNS OF CRACKS. EXAUST MANIFOLDS FAIL? (BOTH?), HEAD GASKETS FAIL? (BOTH?) INTAKE MANIFOLD CRACK? BLOCK CRACK? PLEASE HELP... YOUR THOUGHTS????

 

[tommays]

Re: 4.3L OMC COBRA WATER IN CYLINDERS

try to turn off the caps lock<br /><br />you could have just sucked it in because of the overheat its hard to say<br /><br />i am a long island trailer boater also we flush every trip and have gotten 20 years out of maifolds doing this BUT i think you pushing the limits in anybodys book at this point<br /><br />

<br /><br />i dont no you exact style but if you remove the riser you looking to see if the passages are cloged with scale and the metal is getting thin <br /><br />you cant really see most of the parts that will wear through<br /><br />tommays

 

[Bondo]

Re: 4.3L OMC COBRA WATER IN CYLINDERS

My Guess is Either the Exhaust Manifolds,.. Or the Intake Manifold is the Problem...........<br />The Exhaust is the Most Likely Issue..........<br />The Intake is More likely to drop water Directly into the Oil,.. Instead of the cylinders......<br /><br />BTW,...... Welcome to the forums here at iboats,.........<br />And,.......<br />Loose the Cap-Lock,........... It's Rude,+ Hard to Read...........

 

[Lou C]

Re: 4.3L OMC COBRA WATER IN CYLINDERS

If you have a 1987, it has the one piece "batwing" OMC manifolds, they are hard to find now, I picked up an set from Doug Russel marine but they are very pricey. There is an outfit in Washington State (Sea Way Marine www.sea-way.com) that is selling an conversion kit using Merc 2 piece parts, if you need to replace you can go that way. I changed the OE ones on my 88 in 2004, I have no idea how many salt water hrs it had but they were then 16 yrs old, I was not having any problems but didn't want to take a chance. You can look inside the big center ex outlet and see if there are rust stains there, and maybe you could build a block off plate and air pressure test the manifold with it in water to see if there are leaks by the ex ports. But if the 4 ex outlets are flaking, I'd replace them, use the OE if you can get it because they last a long time and have no riser manifold joint to leak. If they are not available, I'd go with the conversion.

 

[WZNYROBO]

Re: 4.3L OMC COBRA WATER IN CYLINDERS

thanks for the help... (cap lock off, sorry)<br />the inside of the exhaust manifold is very flaky.<br />I stuffed a rag in the exhaust port and put duct tape over the outlets. tested it with air and duck tape rose with the air trigger. however i also checked with water and i'm not sure if the air or water is seeping through the rag. doug russel lists the oe part on the web site. does anyone think the block can be cracked? should i get a "head set" and replace the head, and intake gaskets anyway. i believe i have been getting water in the oil 8 - 9 trips before the overheat (level was high). pushed it hard on the day it overheated (74 miles total) full throtle most of the way. anything else to look for? your thoughts please.......??? (thanks for your help, everyone)

 

[KaGee]

Re: 4.3L OMC COBRA WATER IN CYLINDERS

With water in the cylinder and in the block also, it most likely is from the manifolds as previously stated. A pressure check of the block will determine if there are any internal leakage.