Mercruiser risers

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BillyK

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I need to change out my risers on a 6.2 mpi. I have a 2001 Carver 356 and I try to keep my engine room as clean as possible. What is the best way to remove the coolant and raw water to reduce the mess and then clean up. Are there any pitfalls I should be looking for, and how do you know if the manifolds need to be replaced also.

Thanks for any advice.

Billy K.
 
Drain from both the block and manifold drain petcocks... or coolant hoses if you have a large mouth container.

Factors for replacing manifolds and risers are the width of the wall between the exhaust and water jackets.
 
"...how do you know if the manifolds need to be replaced also."

Once you have the risers off you can visually inspect the inside of the manifolds. You should replace them if: you see rust or scaling inside the water jacket or exhaust passages. Even if they look ok you should replace them if you suspect they are the original manifolds or if you don't know when they were last replaced. Check the torque on the bolts a couple times after you have started using the boat again.
 
A little trick to help save your knuckles from getting scraped and your spark plugs from being broken. Pick up two bolts about an inch longer than you manifold bolts or some threaded rod the same size and an inch or so longer than the manifold bolts. They don't have to be stainless because you won't be leaving them in. If you bought bolts, cut the heads off with a hacksaw so that you've got two long studs. As you remove the outer manifold bolts, replace them with the studs. Then remove the inner bolts. Now you have something instead of your hands holding up each manifold. Slide the manifold off the studs and clean up the block surface. When it comes time to install the new manifolds, loosely screw the studs into the outer holes. Slide the gasket and manifold on. Install the inner bolts. Then remove the studs and replace them with the outer bolts. This way you wouldn't have dropped the manifold on your fingers or on your spark plugs. I did both of those until I learned this little trick. Also, before you install the manifolds or the risers, run a draw file lightly over each of the mating surfaces to make sure they are clean and flat or else you might have some leaks. Good luck. Hy
 
If they're original replace everything! Manifolds,Risers and hardware. The nice thing is now they sell them packaged as a kit everything you need, you supply labor.
Rob
 
If you need to change the risers, you should probably change the manifolds too. They aren't far behind. The manifolds should have drain plugs at the bottom.
Get two threaded studs a little longer than the maniflod bolts for the re-installation.
Thread them in to the outer most holes 9or wherever space allows you to get them), put the gasket in place, put the manifolds in place, start the bolts in the remaining holes, take the studs out, and replace them with bolts.
It will be a lot less frustrating, and your knuckles will be a lot happier too.
It's a good idea to pull a riser off on each motor every year to take a look inside. The risers come off pretty easy, and the gaskets are cheap. I do mine in the fall when the boat comes out of the water.
 
If... the 6.2MPI is full-FWC, the likelihood of the FWC manifolds requiring replacement is very very slim. They should last a long time , perhaps the life of the engine, but take a look from the top any way when riser is off. If you pull a coolant hose off each manifold & drain into a container the remaining level should be low enough to not get into the manifold exhaust passage when you pull the riser.

Suggest you have a shop-vac handy to suck out any coolant or debris that drips in and then plug the manifold mating surface coolant and exhaust passages with a clean cloth to prevent anything from exploring open exhaust valve passages when you are cleaning off all old gasket material, then vac again before re-assembling w/ new gaskets, block-off plates, & studs, bolts & nuts. Remove any excess cast-flashing from the new parts' passages and check to make sure the mating surface deck is flat.

I use a little mild thread-lock on the threads and marine anti-seize on the smooth shaft of the fasteners.

Not sure what Merc says, Crusader recommends 27 ft-lbs torque on manifold/riser(elbow) fasteners. Recheck torque after a few runs.
 
quote:
Originally posted by Brite Idea

If they're original replace everything! Manifolds,Risers and hardware. The nice thing is now they sell them packaged as a kit everything you need, you supply labor.
Rob

Click to expand...


WHY? He has stated that he is concerned about controlling escape of coolant so apparently these are not raw water cooled.

I would probably replace raw water cooled components, but not those that only have a water glycol mixture running through them.

George
 
even raw water cooled mani's last the life of the motor, mine actually was transfered from the first motor that was 20 years used in saltwater.

And the motor would still be in my boat cause it was the head that went, and i pulled a corner bolt hole up installing the head.

Need risers buy risers, i would even bet the mani's are still good.
 
Billy K.
What we need to help is a little more information. Are these the original manifolds and risers? Are the 6.2's fresh or raw water cooled? If they're fresh water cooled are they full or half systems? I'm not going to speculate, I made a quick recommandation based on not enough information.
Rob
 
As he mentioned in the first post, he's concerned about spilling both raw water and coolant in his bilge. So the engine must be FWC. I would hope it's a full FWC system, but if it's a half system, then yes, the manifolds probably need to changed as well. If it's a full system, those manifolds have many more years of life in them.
 
quote:
Originally posted by Chief Alen

even raw water cooled mani's last the life of the motor, mine actually was transfered from the first motor that was 20 years used in saltwater.

And the motor would still be in my boat cause it was the head that went, and i pulled a corner bolt hole up installing the head.

Need risers buy risers, i would even bet the mani's are still good.

Click to expand...


The life of the motor? In salt water? You're a better man then I am. Those things must be made out of some super alloy.

Around here you get about 3 to 5 years out of a set of manifolds and risers that have salt water pumped through them. The OP explained that he was concerned about spilling coolant and raw water, so it sounds like he has a half of a fresh water cooling system.

If you're a gambler, you can take your chances beyond that if you feel lucky. Too risky for me though.

I have a friend who owns an auto repair shop. He is also in to boats and always has a couple of them around the shop. He's been playing around with buying and selling boats for about 30 years.

He usually gets them like this:
A customer stops in and asks "are you in to boats? I see you have a couple here.
reply: Sure!
Customer: I have this boat sitting in my driveway with a bad motor. Will you take it off my hands, or make me an offer for it?
reply: Maybe! I have to take a look at it first.
Every boat he bought in the last 30 years that needed a motor he got because the previous owner didn't change the manifolds or risers, or tried to get away with changing just the risers.

The funny part is that once he opens up the hydrolocked motor to take a look inside, they aren't in as bad shape as you might think.
The motor is shot because of the damage caused by the water getting in to the cylinder through the exhaust port in the head(s), but other than damage related to that ,the bearings and everything else are usually in surprisingly good shape.

He buys them, changes the motor, then usually uses them until someone buys the boat. Then he moves on to the next one.

Last years score was a 24' Searay. Bought fixed, used, and sold. This year he is finishing up a Four Winns, and he has another one already lined up for when this one sells.

He's the only guy I know who always makes money on his boats.

Bottom line: Keep an eye on manifolds and risers on a boat used in salt water. They are easy enough to change, and a whole lot cheaper than a new motor.
 
My friends 92' 3.0 original mani new riser 5 years ago flushed after every use raw water cooled.

Mine already posted.

Another friend 7.4 l crown line raw water cooled flushed after every use.

New risers about 3 years ago 90 vintage original mani's.

List goes on and on.

I can understand if someone doesn't flush or keeps the boat in saltwatwer then maybe needs mani's.

I and friends boat in Raritan bay can't be any more dirty and salty then that.

The list is longer personal friends that have boats. Risers go not mani's

Original poster should line the bottom of his boat with garbage bags.

Catch the drips and what gets in the bilge wash out with water, with the bilge plug out and the bow tilted up.
 
Thanks everyone,

The 6.2 is a closed fresh water system. I will check the manifolds after I take the risers off. Thanks for the tricks for manifold replacementm it will help if they ever need to be done. I will follow you tips to keep the bilge clean and have the shop vac handy.

Thanks again,

Billy K.
 
The install went okay I guess, but I don't see any water coming out with the exhaust. Do I need to run them a little longer. Do they need to be bled, I see there is what looks like a bleeder screw on the top of the riser.

Thanks

Billy K.
 
Did you reopen the main engines' intake seacocks?
 
The holes on the gaskets lined up. This is the raw water side I'm not getting, which is really weird unless there is something I'm missing.

Billy K.
 
I'd check to see if the RW pump is pumping if it is go back to the risers a passage is most likely blocked, are the manifolds RW or FW cooled there's a difference in gaskets to the risers to manifold. Do a search I think someone had the the same trouble last on the site.
 
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