Mercruiser 470 exhaust manifold cracked

[jabfd]

Hello.
I was losing antifreeze so I took off the riser/res. and found the divider in the manifold. Was cracked does any body know where antifreeze is suppose to be and exhaust . To me it looks like both side of that divider both go out the riser and o the leg into the river . So why is it seperated any help would be greatly appreciated thanks

 

[Bt Doctur]

Re: Mercruiser 470 exhaust manifold cracked

that web is usually found with a split that means nothing. only the front of the gasket is slotted so that what you put in the res goes into the system. sure its not the weep hole leaking?

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

Yes I ran a paper clip in the hole and nothing also the riser has a hole that look like instead of the raw water coming out toward the back of the riser and out the exhaust it leaks in the side and can go to toward the head . So your saying the crack in the middle of the two chambers is nothing to worry about . So mabe I just need to replace the riser ? Thanks so much for the response

 

[Bt Doctur]

Re: Mercruiser 470 exhaust manifold cracked

post some pics thru photo bucket ,its free. before you start throwing parts at it.

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

I don't know how to post pics I have them on my phone I can send them by text message or email sorry

 

[Bt Doctur]

Re: Mercruiser 470 exhaust manifold cracked

I`ll send an address in a private message

 

[Bt Doctur]

Re: Mercruiser 470 exhaust manifold cracked

here you go, look corroded quite a bit , was there A/F ion the manifold when you removed the riser or just water.

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

I sent some pics let me know what you think

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

Antifreeze was low so I did not see any . But also I have not ran the boat since Friday . Do you know if that crack seperated exhaust from water

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

Antifreeze was low so I did not see any . But also I have not ran the boat since Friday . Do you know if that crack seperated exhaust from water

update Bt your right the web is craked . and since that only seperates the exhaust cylinder 1 and 4 are the rear and 2 and 3 are in the front so that should not do anything. i think my problem is the riser gasket is leaking into the exhaust and also my riser has a hole letting raw water back into the exhaust instead out of the back and down thru the leg. I hope! so looking for a new riser or use in good shape hopefully that is my problem. i will change the oil and test the engine and let you know how i make out thanks for all the help jeff.

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

Update. I change my oil there was antifreeze and replace riser ran boat for 45 min on muffs checking oil and weep hole for antifreeze nothing yet hopefully this is it. Has anybody ever herd of a bad riser leaking antifreeze into the oil before ? I guess true test is out on the river . Because if its gonna happen its gonna happen out there lol

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

checked boat this morning oil was clean and clear antifreeze down about 8oz. could this be just air bubbles that got out since the system was open or do you think that I still have a problem ?

 

[Eric 3.7LX Alpha 1]

Re: Mercruiser 470 exhaust manifold cracked

could be air.. time will tell.

 

[Bt Doctur]

Re: Mercruiser 470 exhaust manifold cracked

the riser is cooled by the raw water not A/F. A/F can only enter if the mounting gasket was leaking.

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

Ok the gasket and riser are both new , I ran the boat for 25 min after cool down the a/f was a little low about 6 oz I guess next step is to pressure test the exchanger can I pressure test and pull the after plug if I see a/f then I know that I have a leak in the exchanger weep hole is still dry oil is still clear and clean .

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

ok guys heres another update this 470 killing me !!!

so i got tool from autozone and pressurized the system up 15 pounds and it was droping slowly held a while at 11to 13 psibut still droped .So i pumped it back up and looked everwhere for a leak . i found a hose leaking so i tighten the clamp all good there. also found a hose going to the thermostat that was almost busting open took hose off found thermostat housing had a hole .replaced thermostat housing, new gasket and thermostat . pressurized system and droped from 15 to 13psi in 35 mins. looked at the oil still looked clean but a little higher than i thought . Going to try to take it out on the river if after i get back and there is a/f in the oil it got to be head gasket right? Again thanks for everbody reponse Jeff.

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

also i checked the weep hole many times when system was pressurized and was dry .also when engine was running . and i ran paper clip thru to make sure it was not blocked .thanks for your help guys

 

[Live-liner]

Re: Mercruiser 470 exhaust manifold cracked

Good Morning,
Food for thought; The surface of the manifold where the new riser/elbow and gasket sits must be perfectly flat and smooth (no pitting, etching or rounded surface from improper cleaning) I machined mine down to ensure a flat surface after replacing the elbow and still having a leak. It fixed the problem, however you must make sure the manifold is good first.

 

[jabfd]

Re: Mercruiser 470 exhaust manifold cracked

live-liner thanks for reply when i had the riser off i clean and scraped and sanded everthing looked good
are you still having that problem? if that gasket was leaking i would lose a/f but it should not get into the oil right ?

 

[Live-liner]

Re: Mercruiser 470 exhaust manifold cracked

Mine began as a manifold/riser issue but it got to about 120 degrees so I just went ahead and changed the head gasket. I cant see how the a/f would get into your oil from the manifold. However, I'm not a mechanic, just a DYI'er and could be wrong. If you ask my wife, I'm wrong a lot!
Hehehe