Marine Exhaust Manifolds. How Do They Work?
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- čas přidán 26. 11. 2020
- Hey Everyone, Today I go over a boat exhaust manifold and show how they work and how the water cools them. I cover all the basic components of a Marine manifold.
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Excellent job explaining this. Not knowing what a mechanic means when they say this ir that is bad, your explanation makes it crystal clear
Great informative video mate. Just purchased a Maxum with a 4.3 and your video has been extremely helpful as there is a build up of rust on the outside around manifold and riser connection which based on your video I’m thinking an external leak.. time to replace gaskets 👍 thanks for your video.
Cool deal man I work night security at a marina so I see the stuff but no clue what it is and this definitely answered 101 questions.
Thanks for taking the time to make this video. Very informative.
Thanks Tim. I was hoping that somebody would find it useful.0
Excellent explanation for an amateur like me. I appreciate your clear, instructive video.
Thanks Jack. I appreciate that.
1987 Bayliner 2450 Ciera with an omc GM 5.7 with a similar open cooling system. Thank you for giving me a new maintenance project, like I don’t have enough. 😆 You saved me $$$ by giving a diy amateur a bit of good know-how. Thank you. 🍻
And to the other posters with further explanations of the cooling system, thank you to you all, too. 🍻
Thanks very much. Learned a lot. Time to change riser gasket. This vid maybe saved me hours and hundreds.
Great explanation on exhaust manifolds and risers. Thank you.
A most excellent description. Thank You you cause I just learned some stuff.
Thanks. Now I have an idea of what I am up against with changing my Mercruiser manifolds.
Thank you for the video. Getting ready to replace on my boat.
You are a life saver man thank you
Very informative video. Nice job in putting this together. Direct and to the point.
Nice job, never seen the inside till now! thanks!
great video man perfect for getting an idea of how they work ! keep it up
very very nice video.no stupid music and everything is nicely filmed and explained. thank you dude
Glad some people enjoy the simple videos!
Nicely done. Very nicely done.
I was looking for 8.2L Mercruiser cooling system info and I came across this. I'm essentially looking for info in regard to how the entire cooling system functions; I do have a basic understanding of it but I want to know the intricacies of it. Knowledgeable and trustworthy marine mechanics can be difficult to find. I want to understand the system top to bottom/front to rear so that I don't have to wonder if someone knows what they're doing. This does help somewhat. At least now I know that the exhaust manifolds are water-jacketed using sea water, very similar to an engine block being water-jacketed and using engine coolant.
Thank you for doing this.
Subscribed!
But a Mercruiser shop manual.
Thanks for the explanation. I just replaced my '97 model 4.3 Mercruiser V-6 engine in my boat due to the thermostat not opening during winterization and not getting any antifreeze into the block. Lesson learned. I have the 1-piece manifold/risers. Fortunately they seem to be ok. I have taken the boat out a couple of times with no issues thus far.
I was told thermostats have a bypass for this reason. Not true? I've been doing winterization the old fashioned way by draining water from the block and the lower hoses then pouring antifreeze into the hoses I've disconnected at the thermostat. I'm no expert but have had good luck so far. I would love to know any other tricks to ensure I'm doing this correctly. I do not disconnect the risers/riser hoses at all...but I'm working on Volvo-Penta engines....I've never heard of this being necessary.
@@deraeler Same here with our 4.3 merc. Drain water from all 4 drain ports, drain water from power steering cooler water hose and main water pump hoses, done in about 10 minutes. Both block drain ports need a quick clearing with something small as sand/mud accumulates at the bottom. Cold MN winter (-30F) for many years now, no antifreeze, no issues.
Very clearly information. Thanks .Leszek
Awesome explanation - great info! You just got a new subscriber!
Thank you ,very well addressed...
Thank you- great presentation! I learned a bunch!
Great info here. I never saw one apart. Interesting.
Super informative. Thank you for the video!
Great video... Very educational...
very well said and explained...thank you so much.
Dude, you're great! Thanks for the explanation on this.
Thanks mate, very good!
This is great! thank you
Fantastic video!! Thank you for doing this!
Thank you for the explanation, great to know
Thanks, this video was very helpful !
Brilliant...really informative thank you 😊
Great video .. proplems are also inside the riser is a liner type wall that separates exhaust from water .. they tend to rust through .. easy to inspect when u pull it off .. .. be safe
Great video young fellow 👏
Good info bud! Thanks for sharing your knowledge. I’m getting some moisture in a oil but nothing significant. Looks like mayonnaise on top of my valve cover and droplets of water on my oil fill cap. Had mechanic wanting to replace the block thinking it was a blown
head gasket 12k to do the job!!! I will replace the exhaust manifold and risers and see if that will solve my issue with water getting into the crankcase.
Thanks again!
The tiny holes are for water to escape. The manifolds have a built in heat exchanger where water stays in the the jacket around the manifolds to help keep them cool. The water escapes slowly out those holes along with the engine hot water. On the older log style a hose goes to the front and back and has one tiny hole in the restriction plate. A separate hose goes on top of the riser from the water pump. On these the water goes in from ends to end and water pump water comes out thru the bottom thru the big holes out the riser.
I've been told the gasket with the 2 small holes are used on the most common open systems where sea water comes in thru the system and goes out the exhaust. If you have a closed system the gasket is different and the holes are open.
@freshroasted coffee yeah. A closed system is great but I like the raw water. I have a 73 searay. Still going. 302 ford v8.
Great explanation , my kind of videos.
Great Job Brother!!
Good lesson, thanks
Great video, thanks 👍🏻
Vary helpful video, thank you!
Thank you for this video. My boat started is blowing white smoke and running bad. Probably the risers.
awesome video. thanks for the great tips.
Great video. Thanks.
Great tips brother, I’m having water in the oil so I’ll check that out
Good spot to check first for sure.
Just had a Volvo Penta GL 4.3 where an old impeller failure sent fragments into the thermostat, clogging the fitting to the manifold feed on one side. Absolutely roasted the two rubber hoses on the discharge. Even melted the alarm switch.
Always check for failed impeller blades.
Good article very informative. its time to change my gaskets! Gonna use a camera scope to look first though.
That was so good I subscribed
Great Video!
Nice video. Thanks.
Thank you for the video!!
I am getting ready to repair my risers on my 1997 ski Nautique…has the gt-40 engine in it!!!
Definitely wish there were more CZcams tutorials on the step by step of it!!
Thanks for this video tho as it helps to guide a bit!!
Been saving this video for a couple months so that I could reference it with an upcoming riser maintenance job on my 2006 Volvo Penta 4.3gl (I bought it used a few months ago). Unfortunately, I'm now being forced to do this job sooner than I expected because last weekend while in the Gulf, we were cruising FOT and I stood up to readjust my seat but forgot my safety strap was clipped to my shorts. Ignition cut out as expected but then I couldn't restart the engine no matter what I tried. Thought maybe it was the battery died suddenly or starter even. Had to get a tow boat. He tried jumping but the battery was fine. Starter just clicked with no engine turn over so he towed us back in. When I got home I took out the plugs and turned the starter and 2 cylinders shot water out like a cannon. Talked to some boat mechanic friends and they claim the water must have came up backwards through the exhaust system and fed down through whichever cylinder valves were open at that time. Anyone else experience this issue?? Is it common? I should mention that I have raw water cooling. Thankfully, after a few days of turning it over using the starter plus some fogging oil and ensuring there's no water in the engine oil, I was able to get it dry and get it running again. Obviously, I'm nervous about this happening again! I don't think I have any cracks or water in the manifolds but this weekend I'm going to take the risers off to check that and probably replace them since they are original and exposed to saltwater.
When your boat came to a sudden stop, water came up through the exhaust from the outside of your boat. The out drive has flappers that open and close to prevent this from happening. From what I understand, you will need to get these flappers, by taking the out drive off. These flappers have rubber to seal them and prevent water from entering into the through the exhaust during sudden stops. They fail when the engine overheats or gets too hot and since it's rubber they eventually wear out and do have to be replaced. I have watched a CZcams video about it recently because I've been experiencing this same thing.
@@marymeyer1449 Would you happen to have a link to that vid you referenced? I lost an engine because of this (since replaced), and want to have a visual aid on the backflow issue. Thanks!
@@jeffferoce2633 Chris Boats explained in his video of How flappers work. I am not sure how to share it with you, but you can search it.
thanks for information!
Great overview, I was clear on the process. Could you do a similar video on marine engines vs regular auto engines? I have an old 87’ chris craft that has a seized motor and was thinking about picking up a used motor from junkyard and swapping it. Pros/Cons? Boat needs sone serious TLC from needing floors, interior and motor. Trying to salvage it vs taking it to a landfill.
Nice job
I've been told the gasket with the 2 small holes are used on the most common open systems where sea water comes in thru the system and goes out the exhaust. If you have a closed system the gasket is different and the holes are open.
Well done-
Thanks well done you should get a plug for your shop , and sugestion on repairs , welding possible?
THANK YOU!!!
Good job. Of course my system looks completely different but i really appreciate the info.
Thanks Jim. Your system although different should act the same way at least.
Great video. Just the basics- perfect. I already have a job, no desire to be a marine mechanic.
Thanks!
Hey Josh, love the info. Do you do one on thru hull exhaust? Thanks
A wet joint exhaust is shown in this video. Older style. The fuel injected engines found in boats from at least 2000+ use a dry joint which don't have this design flaw where it can leak into the engine and seize the engine. You could still lose an engine with a dry joint exhaust but it not as common. Replace them every 5 years in salt water and you'll never have to worry.
Hey Mike thanks for the comment. That is true that dry joint have less failure. Although i have seen this design on 2010 and plus models for a fact.
Can I convert it to dry joint
The small hole is to create restriction so the pressure can build up .
Thanks David.
very interesting Seems to me if they made the exhaust manifold with a flange that fits up into the riser that would eliminate the possibility of ever having an internal leak. As you said water cannot flow up hill. Just my $.02, I am a car guy. I know nothing about boats. This is actually the first time I have ever seen one of these.
Great video, learned how they work, just bought a boat with volvo penta 4.3 engine that has 2 of these, are they different from mercruisers ? should I go ahead and replace the gaskets? thanks for the help
Hey! Volvo is slightly different. Dame concept though. It would not hurt at all to change the gaskets if there is a sign of any deterioration. Good preventative maintenence.
On a Merc 3.0 thermostat, the hose on the right (as you face it) goes to the exhaust manifold correct? So if I fill that with antifreeze should that not run out the back of the engine? Winterizing my boat myself this year and nothing runs out the back. But the hose does fill up?
Quick question How much pressure to tighten the screw
What are all of the bolts for and how do you remove them? I understand the small 10mm is just drainage plugs but what about the big plugs?
Like the video. Very helpful. Question. Can a bady/ leaky exhaust manifold gasket cause an engine to hydrolock?
It very well could yes.
Thank you! I had 2 mechanics tell me that I had a blown head gasket (water in oil) pulled my 3.0 all apart and found the head gasket wasn’t bad (tested with good compression on all 4). My riser/ manifold were the base of all my problems.
Great to hear. Yes a head gasket seems to be the first thing mechanics will say. Lots of times it is however there are many other possibilities. Riser gaskets are supposed to be changed every 2 years or something by spec.
What about the risers flaps right below. I just took my risers off and don't notice any rust in the exhaust chamber. The issue im having is after a few minutes running, the engine gets so tight to turn, and doesn't. The battery cable terminals melt off, and the engine is to tight to turn by the crank. Happens at the lake. I noticed one of my risers flaps open fully and one closes when I took it apart.
On the older ones (mine anyway) the water just doesn't go in and out , the water flows thur constant and back thru system before being released.
I have 5.0 Merc IO one water jacket is cool and one hot. That normal or both should be cool??
Thanks
I would think that with the invention of cerakote, the manufacturers should be lining the interior of the water jackets to prevent rust through. I'm no engineer but I would think they could do the math on cooling temps and heat transfer/absorption or discharge of heat and figure it out. I would pay the extra cost in the manufacture process to ensure not having a rust through and engine failure.
Not being fluent in cerakote application but versed in powder coat, if cera is electrically applied as is powder, the internal application, especially tight space internal application of electrically charged particles from an electrical power source gun applicator is highly problematic for the device to reach into all the confines of the internals of the water jacket. Serious problem number two, if a custom micro wand head was invented, the uniform application of the powdered substrate would be hindered by Faraday cage effects. Each manifold water jacket would have to be mapped in cad by the design company, sent to the cad/cam cerakote company operator, if there is one, and executed by custom machinery run by a computer. That said, I think you're onto something. As an industry in the US, we have liquid bath coating capabilities ie electro plating that could be an industry ready step process with virgin material from the manufacturer. ...internals still an issue en bathe with Faraday but not as evident. Would certainly tap any contacts in aerospace with internal cavity coatings.
This fail has happened to a boat I just bought, they said it was a head gasket, but couldn’t find the issue till this video.
Should I make my own or just by a new one?
Great information. Calling from New Zealand. How do you feel about these engines running in seawater?
Thank you! Well it can be done and is regularly. I would encourage a saltwater neutralizer wash like a brand called salt off. I can see them being a real nightmare in saltwater and having lots of rust issues. I believe that is why many people run outboards in salt. They still get affected but are easier to maintain.
Plus boats tend to run a cooler thermostat that an automotive engine, I can actually touch the engine block right after running all day and it’s just warm.
Can you reuse the bolts on the risers?
Cool
I have a 4.3 liter Yamaha. I’ve been experiencing some heat issues. Last year I replaced the impeller and the water circulating pump (I did use one from an auto shop, vehicle application). It apparently did not have a thermostat in it since I’ve had the boat for several years. I left it out yet then. Seemed to work well last year with a few moments where it went up to like 175. This year I have an issue again. I can stay at low RPM’s all day long, but 98% of the time, if I go mid to high RPM’s the temperature starts to rise. If I back it off, it generally cools back down at about the same pace. I’m wondering about my risers. There are some water stains on the exterior of the exhaust. I haven’t known until recently that they should be inspected occasionally. I called on gaskets before I tear it open, but they said they’re discontinued. What are your thoughts? Nick
Suggest you try an infrared laser thermometer ... got a cheap one from Harbor Freight couple seasons ago for $20. You'll be able to check the Temps on correlating parts of the exhaust system , side-to-side.
Perhaps it would be beneficial to point out just why marine exhausts are so different from car exhausts. One could think that car exhausts are essentially air-cooled & marine exhausts are water-cooled. Why is this? The marine engine bay is a fully enclosed space, the automotive spaces are open to airflow. The car uses air thru the radiator AND along the exhaust manifolds to extract heat, the marine engine only uses a body of water as the source to extract heat.
Cars have radiators and water pumps.
@@gregwhitehead7967 Perhaps one could think of a car as having a two-stage cooling system, the first being a closed system with a coolant circulating & a radiator using air to dissipate the waste heat into the mass of air around us...In the marine application, think of it as a single-stage system , dissipating the heat into the mass of the body of water its floating in.
@@gregwhitehead7967 marine engines have waterpumps too, and on engines like these they pump raw seawater through the block, heads and exhaust for their cooling.
@@eaxnitro I don't think they pump a lot of seawater where I live, I live in the mountains in Idaho though but yes they pump raw lake water and blow it right out the exhaust. I don't own a boat myself but I have a friend that has three jet boats and another friend that has one really bad ass one
That explanation sounds like a whole nother video
If you have a known issue with hydrolock would you replace only the gasket to see if that does the trick or would you have the manifold tested. If you replace the manifolds, Would you replace the risers also?
If a fresh water boat, i’d replace the riser gaskets only. However a hydro lock can be caused by a bad head gasket as well. Start with the simple stuff though.
Water come out under lower unit right?
Great explanation and video, thank you. I’m a brand new first time boat owner and learning a lot. What if the exhaust water is black and smells like fuel or oil? I just got a freebie 2005 Baylnier 185 that I just got running and noticed the black water coming out of exhaust. It had not been running for over 5 years.
If you roll with Crusader inboards you’ll likely not have to worry about risers or manifolds. Roll with Mercruiser and figure every 2-5 years depending on use and salinity
Cheers
What do you think caused milky oil to come out of my air intake?
Informative video. I have a 1999 4.3 Volvo Penta with water in the #6 cylinder. Do you think it might be the exhaust manifold?
Very very good possibility. However a head gasket could be a culprit. Start with the manifold and see what you can find.
A few questions to ask would be, is the system a closed cooling system or not. If it is a closed coolant system then are you going through coolant? If yes to going through coolant then it is a head or head gasket problem. (This could be big money if the head is damaged) If it is straight Sea, river or lake water cooling then as the previous response said, start with the exhaust manifold. This is obviously the easier one to check. If not, yes you have a head problem. Also I believe the overhaul of the manifolds gasket is every 3 years. The one thing I always wonder is why they don't ceramic coat all these cast iron coolant parts. We used to do this with chiller and boiler heat exchangers and it is amazing the difference it makes... no rusting at all.
What about compression gas in the water. Has misfire and when reved the top water hose swells up. Any ideas.
Could very well be a head gasket issue.
please help me source V8 Merc 260 salt water exhaust parts, I'm on a budget. preferred scrap yard systems that have been preserved
Hello, I got a problem with my boat "milky oil" I replace the head gasket, thermostat, and all gaskets, and everything looked good but the milky oil is there I check the exhaust manifold, and had a big crack on it if I run the engine without the manifold nothing happen, just inspected the intake and exhausts on the block and looks like water gets into there because seems some oxidation, Now I understand why.. i will check the manifold with some pressure just to make sure there are no leaks on it, thanks, man.
No problem at all. Yes check the manifold and the riser gaskets. If cracked 100% get a new/used manifold. Good luck!
@@Schneids15 hello, again I just checked my manifold with air pressure, and apparently, it doesn't have any water leaks inside, so I started to check carefully and found that the corrosion is inside the cylinder head, right where the screws that They clamp then and I found a slight crack in two of them. Do you think that could be the problem because it mixes the water with the oil? thanks.
HI,
Thanks for this informative video.
I have a mercruiser with alpha one Gen 2 , that was overheating, i replaced the impeller and that solved the problem, but my concern is that the water is coming out of the outboard is cold on one side and hot on the other side with weaker water flow.
Does any one know why ? should i be concerned?
Thanks in advance for any replies.
Sam.
Hey Sam. Do you have straight pipes on the boat that you can determine water is cool on one side and not the other? Or are you just feeling the temp of the manifolds?
@@Schneids15 Thanks for quick reply, when i have the engine running with earmuffs , i felt the water that comes out from the bottom of the outboard, and on one side it was hot and rusty in color, and the other side ( Port side ) it was cold , i did not notice any temperature difference when i felt the manifolds, also when i replaced the impeller , i noticed a melted plastic on top of the water pump casing, , i'm guessing it's part of the flapper and possibly more pieces are stock inside of the exhaust manifold restricting water flow? from your experience, do you know if the water should escape cold on both sides?
Do u have a video on how to remove fuel injector rails on a 2012 mercruiser 5.0 V8 engine?
I don’t sorry.
@@Schneids15 thx anyway! 😊
What does it mean when one side is ice cold and the other side is warm to the touch after running for 10 min? 1995 5.0 cobra
Could be a little restriction in one causing it to be a little warm.
Why do they do it this way can they just make plastic guides for this manifold? This happened to my jet ski
Did this come off a boat that was in fresh water ? Or salt ?
I'm a diesel mechanic,not a marine mechanic ,not much anyway. A internal combustion ENGINE...is an ENGINE. A MOTOR is a air or electrical or fluid driven device. That's what a MOTOR is to me. Thanks
So I have a question please,
I’m looking to purchase a used boat where the owner or seller ran into sand bar with his inboard a Mercruiser 4.3 not realizing the motor started to heat up till it stopped and won’t start.
He didn’t flush the motor and didn’t winterize it because he wasn’t able to start the motor.
What is the possible scenario in this situation about what could have happened?
Sounds like that motor had a severe overheat. Sand likely ruined impeller. Will need heads tore off it and head gaskets replaced. Heads may be cracked and likely will need new exhaust bellows. You would be best off to put a new motor in it.