Checking Risers/Manifolds - Sanity Check

M

MC1600

New Member
Oct 4, 2007
304
Wilmington, NC
As some of you may know, I recently learned I was not flushing my engine correctly (using the Perko kit without running the engine). Come to find out, the PO did it the same way.

Given this information, and since the boat is and has been in saltwater, with 350 hours, I will be checking the elbows, risers, and manifolds soon. I figured the price of new gaskets is worth the peace of mind.

My plan is to remove the elbows and risers so I can also inspect the manifold while I'm in there. I have gone through my shop manual for this, but have a couple questions for a sanity check:

1. Can I remove the risers and elbows (and possibly manifolds if need be) without removing the boat from the water? I do not have a means by which I can drain the engine while in the water (ie, no seacock).

2. What am I looking for in there? Is ANY rust or corrosion a sign that I should replace? How much is too much?

3. If everything looks ok, I will be reassembling with clean gaskets and will plan on cleaning out the risers and elbows with freshwater. Is there anything I can/should do to the manifold while I can see in there other than look for cracks/corrosion/etc??

Thanks guys! Like I said, I'm just looking for that step beyond the shop manual to gain a little confidence before I start tearing my motor apart.
 
MC1600 said:
As some of you may know, I recently learned I was not flushing my engine correctly (using the Perko kit without running the engine). Come to find out, the PO did it the same way.

Given this information, and since the boat is and has been in saltwater, with 350 hours, I will be checking the elbows, risers, and manifolds soon. I figured the price of new gaskets is worth the peace of mind.

My plan is to remove the elbows and risers so I can also inspect the manifold while I'm in there. I have gone through my shop manual for this, but have a couple questions for a sanity check:

1. Can I remove the risers and elbows (and possibly manifolds if need be) without removing the boat from the water? I do not have a means by which I can drain the engine while in the water (ie, no seacock).

2. What am I looking for in there? Is ANY rust or corrosion a sign that I should replace? How much is too much?

3. If everything looks ok, I will be reassembling with clean gaskets and will plan on cleaning out the risers and elbows with freshwater. Is there anything I can/should do to the manifold while I can see in there other than look for cracks/corrosion/etc??

Thanks guys! Like I said, I'm just looking for that step beyond the shop manual to gain a little confidence before I start tearing my motor apart.
Click to expand...

I just did this last season because the boat was new to me and the previous owner told me the manifolds and risers were replaced at the end of the previous season. They couldn't back up the claim with reciepts though so I just wanted to check for myself to be safe, and I was lucky to find that the previous owner was telling the truth. I went all the way and removed the manifolds from both engines too.
I did it with my boat in the water. Just make sure the open end of the exhaust hoses (the big fat ones coming off the risers) are above the water line and you should have no problem.
Once you have them off and on the dock, check for rust and/or corrosion in the walls inside the manifolds and elbows. Use a screwdriver or similar tool to scrape and poke around in there. You want to make sure that the walls that seperate the water from the exhaust gases are solid. If you see any bad spots chuck the manifolds and risers and buy new ones. If there is any bad spots in the walls you will suck water into your cylinders through the exhaust ports in the heads and that will be the end of your motor.
If you do replace the manifolds and risers, spend the extra money and get the ceramic coated ones. They will probably last an extra couple of years.
It is a pretty simple DIY job.
Good luck!
 
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Its not a hard procedure to do, but make sure you know what your doing. My next door neighbor just opened his up two weeks ago. After reinstalling all of it, and trying to start it he discovered he had hydro locked a few of the cylinders. I guess when splitting the halves he let water roll into the bottom half which ran straight into the cylinder. Be careful!!!
 
beachcombersc said:
Its not a hard procedure to do, but make sure you know what your doing. My next door neighbor just opened his up two weeks ago. After reinstalling all of it, and trying to start it he discovered he had hydro locked a few of the cylinders. I guess when splitting the halves he let water roll into the bottom half which ran straight into the cylinder. Be careful!!!
Click to expand...

Splitting the halves of what?? Now I'm a little confused. My plan was to start from the top and work my way down (remove exhaust at top, remove elbow, remove riser, remove manifold).

Is there a secret to preventing what you discussed?
 
MC1600 said:
Splitting the halves of what?? Now I'm a little confused. My plan was to start from the top and work my way down (remove exhaust at top, remove elbow, remove riser, remove manifold).

Is there a secret to preventing what you discussed?
Click to expand...

I'm not sure what setup you have. His was a 91' 4.3 with wet joints. He started with the upper half, and left the lower half still on while doing that check... He ended up pulling a plug only to have water roll on out. If it had been a different stroke, he could have done some major damage.
 
Ohhhh...I think I have a slightly different set-up, but I will most certainly be careful. I picked-up the gaskets today, and talked it over with the owner of the marina. I only got the gaskets for between the manifold/riser and riser/elbow. He said if there are any issues, I will see evidence of it in there. So, I'm not even going to pull the manifolds unless I see an issue with the other pieces. I am hoping this will be a rather simple unbolt, check, and rebolt process.

Just needed the boost of confidence from you guys to jump in there ;)
 
Be sure you pull the hose off the bottom of the manifold before you remove anything else, this will drain out the water that beachcomber was referring to. After your motors are shut down after use, there is usually water(raw water or antifreeze when fresh water cooled) still in the manifolds/spacers/and elbows. If you dont drain them before you split the joint on the elbow the water can drain down into the exhaust port then the cylinders. hope that helps.
 
You should not need to haul the boat.
First, drain the manifold, risers (if installed), and elbows. There are drains on the bottom of manifolds that unscrew. Both the risers and elbows have small brass plugs. Pull them all and drain everything. Use a small screwdriver to clean out any foreign material in the drains to make sure that all of the water is gone. You'll spill water into the exhaust ports if you don't do this.

Loosen the hose clams on the elbows. Unbolt the elbows. Slide the hose rearward off the elbow. Pull the elbow up. There will be some rust, but if pieces are missing or there is a lot of metal gone, replace them. There should be two pipes exiting the elbow. The outer one is where the exhaust tube clamps. The inner one separates the exhaust from the water flow. The top of the inner one should have a "chute" to direct the water flow. IF the chute is bad, or the inner tube is badly rusted away, replace.

Best regards,
Frank
 
Sublimetime said:
Be sure you pull the hose off the bottom of the manifold before you remove anything else, this will drain out the water that beachcomber was referring to. After your motors are shut down after use, there is usually water(raw water or antifreeze when fresh water cooled) still in the manifolds/spacers/and elbows. If you dont drain them before you split the joint on the elbow the water can drain down into the exhaust port then the cylinders. hope that helps.
Click to expand...

Ok, I get what you're saying, but if that drain is below my water line, will it ever actually drain?
 
fc3 said:
You should not need to haul the boat.
First, drain the manifold, risers (if installed), and elbows. There are drains on the bottom of manifolds that unscrew. Both the risers and elbows have small brass plugs. Pull them all and drain everything. Use a small screwdriver to clean out any foreign material in the drains to make sure that all of the water is gone. You'll spill water into the exhaust ports if you don't do this.

Loosen the hose clams on the elbows. Unbolt the elbows. Slide the hose rearward off the elbow. Pull the elbow up. There will be some rust, but if pieces are missing or there is a lot of metal gone, replace them. There should be two pipes exiting the elbow. The outer one is where the exhaust tube clamps. The inner one separates the exhaust from the water flow. The top of the inner one should have a "chute" to direct the water flow. IF the chute is bad, or the inner tube is badly rusted away, replace.

Best regards,
Frank
Click to expand...

Thanks Frank!
 
MC1600 said:
Ok, I get what you're saying, but if that drain is below my water line, will it ever actually drain?
Click to expand...

Yes. No additional water is being pumped up into them when the engines are not running.
 
Thanks to everyone for the vote of confidence! I was able to get the stbd side done today, and will do the port side tomorrow. All in all, you were right, and this was a very simple task. After speaking with a local Merc expert, he told me not to worry about draining anything since I wasn't removing the manifolds.

I got a small scare when I removed the riser because some water seeped out from the water passages, but it ended-up being nothing at all - just a dribble. Cleaned-up the old ones, and put them back on because they were in EXCELLENT shape!

Thanks again guys!!
 
Oh, I forgot. The other thing you want to check is that there is no rust or signs of water in the exhaust (central) part of the exhaust manifold. Check the bottom and also the cylinder heat area near the exhaust valve passages. A small inspection mirror, like a dentist uses, helps.

Best regards,
Frank
 
fc3 said:
Oh, I forgot. The other thing you want to check is that there is no rust or signs of water in the exhaust (central) part of the exhaust manifold. Check the bottom and also the cylinder heat area near the exhaust valve passages. A small inspection mirror, like a dentist uses, helps.

Best regards,
Frank
Click to expand...

Done, and done! :thumbsup: Thanks Frank. She still looked nearly brand-new in there. In fact, the only place I found ANY rust during the whole process was in the actual exhaust end of the elbow. Had a couple other guys check it for me too while she was all opened up, and everyone said everything still looked near-new! :smt038
 
That's good news!
At least now you've seen inside there for yourself and have a baseline for future inspections.
 
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