How to test exhaust manifold or riser for water leaks?

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kneedragger

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OK, Winter time maintenance. on my '94 4.3L Mercruiser. Winterized completely (removing all the water in the motor) in October of last year. I just got through changing all the bellows (shift bellows had not been changed, and was leaking), and gimble bearing. I have removed the motor cover to have it reupholstered, and have the boat covered with a canvas trailer able cover out side. I finally got everything back together, and it would not turn over. So, I remove the outdrive, thinking it may be in a bind or something. I try and turn it over, and it still won't.

I removed the spark plugs, and water comes out. After an oh ****, I check my engine oil by the dip stick, and there is no water in it (yet) I turn the motor over, and out comes water--Mainly from the two front (flywheel side) cylinders. After turning it over I have water in the oil. Remove oil and filter, and put in fresh. Run the motor, and it runs fine, idles fine. Drain and repeat 2 more times.

All this time, running only for a short period of time without water connection checking temperatures, ( I could always touch the exhaust manifold with my bare hand during this process),and with out the out drive attached.

Now I am ready to attach my outdrive, and check for water again. My question is--IS THERE a way to check my riser and manifold to see if the water jacket has corroded through,and letting water into my exhaust side? Before I go an contaminate the oil, and motor again? Could I have gotten rain water in through the carb? My spark arrestor was on almost all of the time.
Thanks for your help in advance.
 

NHGuy

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Re: How to test exhaust manifold or riser for water leaks?

Alabama huh, are you a salt water boater? You might just do the manifolds and risers as a smart play.
But I have seen folks on here that test em by blocking off one end and filling the other end to the top with acetone. Acetone molecules will fit through smaller cracks than water so they are a good testing fluid. It's hard to make up a pressure tester due to the shape of the water jacket.
If it rained when the spark arrestor was off that could have watered your motor. Not likely though unless it really got a good slug in there.
I hope you dodged the bullet...fingers crossed for ya dude.
 

kneedragger

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Re: How to test exhaust manifold or riser for water leaks?

Alabama huh, are you a salt water boater?
Fresh water only. Never been in salt. This one anyway.

"But I have seen folks on here that test em by blocking off one end and filling the other end to the top with acetone." --How is this done? Which end is blocked off, at the rubber connection to the Y pipe?

Sounds as if I need to remove them to check for leaks no matter what. Lord, I did not want to do that. Hell my wife is already pissed it has set in the driveway this long:)
 

achris

More fish than mountain goat
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Re: How to test exhaust manifold or riser for water leaks?

If the manifolds and elbows are still original I'd bet the house on them being corroded through.

Removing manifolds is a very simple job, shouldn't take more than 30 minutes (including the coffee break :D). If you need to replace both manifolds AND elbows (which I suspect you will), then now is the perfect opportunity to go to the newer style 'dry-joint' manifolds... I've have those on my engine still new (2006) and they look like they'll last another 6 years easily.

If you need part numbers let me know, as they are NOT the same as the current issue (7? down angle as opposed to the current 15?)

Chris.....
 

kneedragger

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Re: How to test exhaust manifold or riser for water leaks?

If the manifolds and elbows are still original I'd bet the house on them being corroded through.

If you need part numbers let me know, as they are NOT the same as the current issue (7? down angle as opposed to the current 15?)

Chris.....
Chris---Thanks for the response. Please send me the "new and improved" part numbers.

My true question remains. Is there a way to test these parts without removing them?

I don't mean to whine, its just I had budgeted and planned for the bellows, and the special tools required to do the job. Spending the $400-500 for new manifolds and elbows, just puts us in a bind. I need an economical solution.
 

Bondo

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Re: How to test exhaust manifold or riser for water leaks?

Chris---Thanks for the response. Please send me the "new and improved" part numbers.

My true question remains. Is there a way to test these parts without removing them?

I don't mean to whine, its just I had budgeted and planned for the bellows, and the special tools required to do the job. Spending the $400-500 for new manifolds and elbows, just puts us in a bind. I need an economical solution.

Nope....
 

achris

More fish than mountain goat
Joined
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Re: How to test exhaust manifold or riser for water leaks?

Well after reading this. The one peice design manifold is not the way to go.

Absolutely correct. AVOID the batwings.

Dry-joint manifolds -> -864612T01
Dry-joint elbows -> -864309T01
Elbow gaskets -> -27-864850A02 (Standard cooling, NOT closed)

Chris.....
 

boattoy

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Aug 21, 2010
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Re: How to test exhaust manifold or riser for water leaks?

Just went through this on my 4.3. Just buy all new everything, cheaper then ruining a motor. I got everything ,manifolds,risers,gaskets,plugs,drains. sierra brand. boat runs AWESOME! in the grand scheme of things its very cheap insurance. The original design IMO is fine If you just drain em. the manifolds that came off my boat were original from 1990 with 600 hours, boat was not taken very good care of either.
 

Curtis1593

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We have twin 350 Merc cruiser‘s in boards. We had one engine on the port side that would run most of the day and seem to overheat after you come in to the Inlet and slow down. After several months of changing things a friend of mine Dan said let’s pressure test the freshwater side. We put 14 pounds of pressure and it held. Then we crank the engine and D thermostat open up. Then we started seeing a pressure drop not much but a little. I looked over the side and seeing signs of some anti-freeze getting into the raw water. We had replaced the manifolds and the risers and all the hoses. Here’s what we found. Putting on the starboard riser was hard the deck constantly got in the way literally had to take a pro bar and push up on the engine to get it to slide in. We cut out a small portion of the top deck
so that we could slide the riser in and out easily. When I removed that side the gasket between the riser in the manifold have been correct the first time that crap in the gasket leak under pressure very little hard to see. After months of frustration we solve the problem . I wanted to let everybody know what we found we had two very good mechanics that couldn’t solve the problem. I had told them that I had replaced everything which I had but that crown was causing the problem and took hours before the engine would actually get hot Just wanted to let anybody that’s interested no check your gaskets are very cheap thing a $15 gasket was the problem
 

Bt Doctur

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Aug 29, 2004
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Wouldnt be the first motor to have water ingestion thru the flame arrestor mounting bolt
 
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