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| Mercruiser 5.0 cracked intake manifold https://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=15433 |
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| Author: | 1baddoggy [ Tue May 02, 2017 10:14 am ] |
| Post subject: | Mercruiser 5.0 cracked intake manifold |
Good morning all. I recently purchased a 2007 Horizon 210 with 5.0L Mercruiser (cabuereted). This morning, I was looking for a place to mount a shoot-thru hull transducer. In the process of that, I found what looks to be a broken off freeze plug in the billage. While looking around, I saw several cracks on the starboard side of the intake manifold. The cracks are between the bolts on top and are big enough to fit my fingernail in. Before buying the boat, we test drove the boat and all seemed fine and we've had it in the water a couple times since then with no issues. We have had a couple of nights since then where the temps hit slightly below freezing for 3-4 hours on a couple of different nights (temps were up to around 50 degrees during the day), but I'm told that was probably not enough to freeze anything up. We keep the boat inside a non-heated storage shed. I am new to I/O motors, so I really don't know what I should be looking for. The guy at my local marina said to put it in the water and run it at about 1500RPM until the temp hits about 150-170 degrees, then check the oil to see if it's milky. Anything else I should look for/check? He mentioned checking to see if the freeze plugs are pushed out and/or if one is broken off. Unfortunately, I do not know how to do that. If the manifold is cracked due to freezing, are there other things I should expect to have to deal with? Thank you in advance for any advice you can share. Jamie |
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| Author: | BrentC5Z [ Tue May 02, 2017 11:15 am ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Agree with what the mechanic said. Gonna have to run it to see if there are leaks etc. Get a mirror to look at the block freeze plugs. They are below the exhaust manifolds. Is your boat equipped with the air pump and Schroeder valve? If so, see if water dumps out when pressurized (if it will pressurize). Block freeze plugs are just discs that are pressed in the sides of the block. probably 2" diameter. 2 on each side. |
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| Author: | 1baddoggy [ Tue May 02, 2017 11:21 am ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Upon further research, what we saw in the billage is a broken drain plug like this: http://i.ebayimg.com/images/g/pVkAAOSwI ... s-l500.jpg I do not know if it has and air pump and Schroeder valve. How can I determine that? |
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| Author: | 1baddoggy [ Tue May 02, 2017 12:02 pm ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Couple more questions. Is there any risk of causing further damage while doing the above testing? Also, regardless of whether there's water in the oil or not, don't I have to replace the intake manifold? |
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| Author: | BrentC5Z [ Tue May 02, 2017 1:15 pm ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Check your oil dipstick for water before you start it. If it looks like chocolate milk, no need to go further. I'd like to see a pic of the intake crack. It has air and water passages as well as creates a seal from the lifter valley (crank case pressure). Pretty good chance it could be sealed/welded vs. replacement. If you have one of those water plugs broken, there should be quite a bit of water in the bilge. should be an easy fix based on the location for getting whats left in there unscrewed. |
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| Author: | 1baddoggy [ Tue May 02, 2017 1:23 pm ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Thanks for your help, Brent. We checked the dipstick at the marina, and it looked clear, but he said it was a little high, which could be indicative of water sinking and raising the oil level. He thinks if there's water in there, it will show on the dipstick after running it. The oil in there was still new (not black), so I'm not sure if I'll be able to tell if it has water in it. I will try and get some pictures of the cracks this afternoon. If there is water in there. Besides replacing the manifold, what would need to be done? He seemed to think that the block probably wasn't cracked or it would be running bad, which it isn't.... yet. I will visually inspect for any leaks I can see and get a mirror to check the freeze plugs. Anything else I can check? |
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| Author: | BrentC5Z [ Tue May 02, 2017 1:44 pm ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Make sure the broken water plug has already been replaced. You'll find out really fast when you start the engine... And you'll have no doubt if water is in the oil. Fresh or old oil, water will bead up and be whipped in the oil. |
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| Author: | LouC [ Tue May 02, 2017 1:56 pm ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
You can also look under the valve covers for a milky emulsion that's what water in the oil looks like. Sometimes it shows up faster there than on the dipstick |
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| Author: | 1baddoggy [ Tue May 02, 2017 2:06 pm ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Is there any reason I need to put it in the water to do this, or can I just put it on the muffs with the hose? The guy at the marina had mentioned putting it in gear. |
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| Author: | BrentC5Z [ Tue May 02, 2017 3:31 pm ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Makes no difference. |
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| Author: | LouC [ Tue May 02, 2017 4:51 pm ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Those plastic plugs are drain plugs not freeze plugs. You might just make sure you don't have water in a cylinder as well since if it sits in there it will rust the cyl walls. You can remove all the spark plugs, disable the ignition and crank the engine over. If no water comes out great if it does blow it all out by cranking, then spray some fogging oil in each cyl crank again then fig some more. Replace the plugs and drsin the water out of the block & heads to remove sources of leaks. Also drain the exhaust msnifokds to be on the safe side. I know on the late model v6 there is s drsin plug on the front of the intake manifold that needs to be removed to fully drain. Not sure if this is true on v8s too. Those intake manifolds don't crack for no reason but it's not clear if it was really freeze damage in this case. |
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| Author: | 1baddoggy [ Tue May 02, 2017 9:10 pm ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Ok, ran it on the muffs and let the thermostat open. Shut it down and checked the oil. No signs of water and it ran just fine. the broken off drain plug is from an old one, presumably broken when it was removed. All drain plugs are in tact. No leaks anywhere, and all the freeze plugs are in tact. I had a guy tell me tonight that no water passes through the intake manifold, so there was nothing to freeze and crack the intake manifold. Does that sound correct to you guys? Not sure what else would have caused those cracks and not damaged anything else. |
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| Author: | LouC [ Wed May 03, 2017 4:20 am ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
That guy was obviously not a mechanic, or at least not one that ever worked on a Chevy small block! Think about it, water has to pass through the intake manifold, that's how it reaches the thermostat! On most Chevrolet small blocks, there is a water passage directly below the thermostat housing that connects with the the cylinder heads on both sides. http://www.michiganmotorz.com/mercruise ... -3543.html http://www.michiganmotorz.com/vortec-ca ... p-465.html Look at the pics that show the underside of the manifold, see the 4 intake ports, there is one for each intake valve. Then the 2 small ports off to the side, these are water transfer ports. When the engine is cool, take off the oil cap and stick your finger inside the valve cover and see if there is a watery, mayonnaise like emulsion in there. If not then you maybe fine. The cracks in the intake, were they leaking water? Are they really cracks or just casting marks? |
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| Author: | 1baddoggy [ Wed May 03, 2017 8:19 am ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
Thanks, Lou. I'm obviously no mechanic. No water leaked from those cracks the entire time it was running. There's no sign that water has ever leaked from there. I meant to get pictures of the cracks last night, but I completely forgot. I'm fairly certain they are cracks because I can stick my fingernail in them. In the picture below, the red circles show where the cracks are. To be honest, The cracks are on the starboard side only. 
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| Author: | rpengr [ Wed May 03, 2017 9:26 am ] |
| Post subject: | Re: Mercruiser 5.0 cracked intake manifold |
1baddoggy wrote: Thanks, Lou. I'm obviously no mechanic. No water leaked from those cracks the entire time it was running. There's no sign that water has ever leaked from there. I meant to get pictures of the cracks last night, but I completely forgot. I'm fairly certain they are cracks because I can stick my fingernail in them. In the picture below, the red circles show where the cracks are. To be honest, The cracks are on the starboard side only. You may be in luck. Those locations you circled should not have water passageway there. Those are low points that tend to collect dirt and water that falls on the engine. Your "cracks" may be as simple as crud layer that was painted over by a previous owner or mechanic. Then the paint/crud cracked. I would scrape away all the paint over those cracks down to bare metal to see what's really going on there. If those are really cracks that go through the metal, then that could allow rainwater and dirt to get through to the area below, which is were your lifters are. That water/dirt would get in your oil. However it is unlikely that you would have actual cracks at those locations. |
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