4.3L Cobra Water Circulation Issues - Out of Ideas?!

[abp]

Started boat on muffs to dewinterize (ran fine on muffs when winterizing) and engine began to overheat. Shut off motor, pulled impeller, and it had burned up.

Installed new impeller kit and started boat. This time I immediately checked drive for exhaust. NO water coming from any exhaust ports on the drive. Immediately shut off engine to save new impeller.

Pulled new impeller kit and bumped ignition to ensure impeller shaft turning. Pulled raw water line from T-stat housing and flushed to rear with good flow out of the portside impeller port. Flushed water through starboard port down to raw water intake openings with good flow. Flushed both hoses from t-stat housing to exhaust manifolds with good flow out exhaust.

Replaced everything, put boat in water started motor with raw water line removed from t-stat housing. Very good flow from impeller.

Any ideas on why I'm getting flow to T-stat housing but no flow from exhaust? Problem occurred while sitting in driveway over the winter.

Thanks for your help/suggestions!!

adam

 

[HT32BSX115]

Re: 4.3L Cobra Water Circulation Issues - Out of Ideas?!

Howdy,


Well, if it's a salt water engine and/or the manifolds & risers are REALLY old, you may have blockage due to rust in them.

You also may have blockage due to previous impeller failures/disintegration clogging the oil, power steering cooler or t-stat. Or in some cases, a plugged y-pipe(clogged with a broken/mangled shutter/flapper)

 

[abp]

Re: 4.3L Cobra Water Circulation Issues - Out of Ideas?!

Thanks, it's an '86 4 winns horizon 195 and the risers are original. Boat was used in fresh water only until about 4 years ago.

So are you suggesting the next step is continued flushing - the problem most likely being a clog?

adam

 

[HT32BSX115]

Re: 4.3L Cobra Water Circulation Issues - Out of Ideas?!

Thanks, it's an '86 4 winns horizon 195 and the risers are original. Boat was used in fresh water only until about 4 years ago.

So are you suggesting the next step is continued flushing - the problem most likely being a clog?

adam

It's POSSIBLY a clog.


The water that cools the engine comes from the raw water pump in the drive.

It is pumped up to the T-stat housing and on to (and through) each exhaust manifold and up through the riser.


It then exits out along with the exhaust through the y-pipe.

Now, you didn't indicate the year model, but if the manifolds (and/or risers) are getting clogged with corrosion the water flow though them and remembering that ALL the water from raw water pump MUST exit though the risers.....(It cannot go anywhere else) If it cannot exit, the total flow of cooling water will be reduced.

That will absolutely contribute to over heating.


It usually manifests itself in one manifold/riser getting hotter than the other (because they do not usually clog exactly equally)


If you have an older OMC and you have the other type of (combined) riser/manifolds like the second picture. Consider yourself lucky they didn't ruin your engine.....


Around 1995 model year....

1990 model year.....

 

[abp]

Re: 4.3L Cobra Water Circulation Issues - Out of Ideas?!

Thanks, it's an '86 4 winns horizon 195 and the risers are original. Boat was used in fresh water only until about 4 years ago.

It has the one piece manifolds, thanks for the diagrams.

adam

 

[HT32BSX115]

Re: 4.3L Cobra Water Circulation Issues - Out of Ideas?!

Thanks, it's an '86 4 winns horizon 195 and the risers are original. Boat was used in fresh water only until about 4 years ago.

It has the one piece manifolds, thanks for the diagrams.

adam

Yeah...I re-read and saw that (great attention to detail huh?):redface:

The one piece manifolds.

I don't know if you can buy them nowadays... I am somewhat surprised that they have lasted this long(and haven't destroyed your engine)

Manifolds that old that have been run in salt (at all) tell me there's a good chance that they're pretty well clogged.


Those type manifolds also have a tendency to leak internally and allow raw water into the exhaust after you shut down. It runs back into an open exhaust valve.....(the result is predictable)


I think Doug Russell lists that type of manifold for an 86. You don't want to know the price. I don't think anyone makes them anymore.... They're NOS parts (New-Old-Stock) and anyone that has them just charges whatever the market will bear.

There are different center-riser kits available I think. You'll have to shop around.

I think you can buy a kit for around $900 or so.

Here's one example.

http://www.ebasicpower.com/pc/BPIOM...s 86-90 OMC 262 4.3L V6 1-Piece Manifold.html

 

[abp]

Re: 4.3L Cobra Water Circulation Issues - Out of Ideas?!

Got the water flowing again!!

Thanks for all of your help. Today I pulled the t-stat housing and flushed the lines to the manifolds with good clean water coming out of the exhaust. Took the housing to a local service yard to get a new gasket and replace the t-stat while i was at it. Lucky me the shop owner was nice enough to sand blast the inside of the housing to clean it out well. I was unaware of the channel inside the housing body that bypasses the t-stat and sends water directly to the exhaust - not very big and could have easily been clogged.

Reassembled housing and hoses and started engine. This time i jumped to the back and forcefully held the muffs tight against the intakes to ensure the impeller was primed. A couple of seconds, and out comes the water from the exhaust. Ran the boat to t-stat temp and it settled in, with manifolds cool to the touch.

Not sure which part was the fix, if it was simply pressing the muffs tight I wasted a lot of time - used the same muffs and hose for years and that has never happened. Good thing is i have a clean housing, new t-stat, impeller, and running boat for about $75.

I had been warned by a mechanic a couple of years ago that those manifolds would eventually wear out and I was going to be in trouble! Guy at the shop today said the second he gets a set they are gone, and for close to a thousand a piece. My dad bought this boat new when i was 9 yrs old, so i guess i plan on driving it until it breaks for good.

Thanks again for the helpful advice.

adam

 

[HT32BSX115]

Re: 4.3L Cobra Water Circulation Issues - Out of Ideas?!

Good for you. You found the clog.


I would not run those manifolds very long without replacing them though.

They are more than 20 years old. You ARE running on borrowed time. When they do fail, they will destroy the engine if you don't detect the failure immediately.

Guy at the shop today said the second he gets a set they are gone, and for close to a thousand a piece. My dad bought this boat new when i was 9 yrs old, so i guess i plan on driving it until it breaks for good.

I wouldn't waste my money on the old type manifolds! Get the newer type for the cheaper price.


On a boat that old, if you allow the engine to be destroyed, the boat will probably be worth nothing. It'll have to go to the big boat cemetery in the sky!!

Good luck!



Rick

 

[Randy J]

Re: 4.3L Cobra Water Circulation Issues - Out of Ideas?!

ok on cobra v-6 another thing is the thermostat my boat never had a heat issue till i decided to take off the thermostat housing and check it out.. seen the original thermostat was old and sorta rusty looking so it took it out and put it back in... then at lake short time for the very first time motor got warm so back to trailer and home..ordered a new one and put in .. back to lake cool as a cucumber
so i guess it was stuck in the open position all the time till i monkeyed with it...moral of story i spos'e is it aint broke dont fix it

 

[Bondo]

Re: 4.3L Cobra Water Circulation Issues - Out of Ideas?!

ok on cobra v-6 another thing is the thermostat my boat never had a heat issue till i decided to take off the thermostat housing and check it out.. seen the original thermostat was old and sorta rusty looking so it took it out and put it back in... then at lake short time for the very first time motor got warm so back to trailer and home..ordered a new one and put in .. back to lake cool as a cucumber
so i guess it was stuck in the open position all the time till i monkeyed with it...moral of story i spos'e is it aint broke dont fix it

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