First year with '97, prolly smart to do Water Pumps/manis/risers...on the v-drive 5.7s '97 300da

YeOldeStonecat

Active Member
Jun 10, 2018
332
Waterford, CT, boat in Deep River, CT
Boat Info
'97 300 DA "Me-Shell"
Engines
Twin 5.7 V-Drive
Re: the manifolds and risers.....thought I took more pics over the summer but below is all I found. From what I have learned of the boat, she has spent more of her life in river water...thus mostly fresh. Her first years in the Pawcatuck River RI (not sure how far up so likely 50/50)..and then most of her life in the CT river around Essex/Deep River (we bought her in Deep River). Likely many weekends out in salt water of course.

When we bought, prior owner stated risers replaced in 2012. Approx 650 hours on the engines.

I'm thinking I want to at least pull them all and inspect...replace if necessary, or clean up and put back with new gaskets if still appear in good condition. Looking around for informative sites to learn how to determine "how they look"..if still good, or not.

I'm sure pictures of the mounted/exterior can't tell much...since what counts is on the inside.

As for water pumps...I'm guessing they are a pain to replace on the backwards engine V-Drives? I have no idea when last replaced (if ever)..but figure they should be done. Thinking the whole unit...not just the rubber impeller. Gotta pull the exhaust (heat exchanger) out? Which I likely have to do anyways to replace the H2O heater in the back.

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Smart to do the exhaust.on a new to you boat.
Shop around for complete kits for the 5.7 that includes OEM manifolds, risers, gaskets, bolts. Should be able to find them for around $600 per engine.
Maybe take the opportunity to install a fresh set of plugs and some new ignition wires while you have the exhaust off.
Impellers are another good investment. Check for signs of leaking around the pumps like rust from what may be a drip or spray coming from a pump. If the pumps themselves aren’t leaking then they’re probably fine.
Making sure the antifreeze is fresh and the heat exchangers are in good shape are another worthwhile winter project on a new to you used boat is is taking the opportunity to inspect and replace any hoses or belts if needed.
 
Plugs and plug wires and distie rotors and caps were replaced soon as we bought her.
Picture was from early summer....I think the plug wires in the pic are the new ones. I've slowly been cleaning up the engines and engine bilge area since these pics were taken.

Question...are those black plastic rectangular intake covers necessary? Or most cosmetic? I know under them there is the typical round air intake with flame arrestor. Reason I ask..the starboard engine...the hole in the center where it mounts to the stud of the air intake flame arrestor...the plastic is all cracked around that and she just spins around loose. Suppose I could glue it or fabricate some backplate out of something..but I almost prefer just having the basic round air intake and intake manifold just be up top naked.

Assuming since I have a '97...before Merc converted over to Dry Joint around 2002 years....I can find a compatible dry joint system? I didn't know what it was but just read up on it and it sure makes sense to covert to dry if I can.

She is a closed water cooling system if that makes a diff (I don't think it does when it comes to manifolds and risers..but correct me if I'm wrong)
 
Tough to tell with those pics but looks like you have what is known as a half closed cooling system. After exiting the heat exchanger, the raw water enters the bottom of the manifolds and mixes with the exhaust while exiting the riser. In that event and at 6 years, it would be a good idea to just replace them for peace of mind. A full system has coolant circulated through the block and manifold which will most often extend their life to that of the engine. With the full system, the raw water is introduced into the riser and there will be a block off plates/gaskets between the manifolds and risers.
At 20 years old, if you have access with a mirror or phone below the engine, you should try to give the oil pans a good look for corrosion as well. Nice to catch them before they dump their guts while under way which can lead to a catastrophic failure.
 
It’s a very straightforward replacement, just heavy parts.

Search around here, many posts about DIY.

If you can change a tire, you can replace manifolds.

No need to pay them $6k
 
Looking for some general tips/pointers on the manifolds/risers.
What are some common "surprises/gotchas" I might run into?
I did some searching of these forums...but the search gods weren't nice to me with much for results. If someone knows of a good "play by play" long thread with pictures and lots of advice..I'd be obliged!

Going back to my yards mechanics note that my #6 cylinder spark plug on starboard engine had signs of rust on the tip..so he suspected a little water and recommended the manifold/riser replacement. Engine did run fine for rest of the summer and oil was just black..not milky..when I changed it just before haulout last fall.

I'm hoping to tackle this in a month or so...before she gets put in the water. Or should I wait until it does get put in the water..and then run the engines to warm them up? I read warming them up can help with those bolts coming free. (less chance of snapping a bolt in the block!)

Wish I had better pics of the engine bay. My year/model..it's tight in there!
 
Looking for some general tips/pointers on the manifolds/risers.
What are some common "surprises/gotchas" I might run into?
I did some searching of these forums...but the search gods weren't nice to me with much for results. If someone knows of a good "play by play" long thread with pictures and lots of advice..I'd be obliged!

Going back to my yards mechanics note that my #6 cylinder spark plug on starboard engine had signs of rust on the tip..so he suspected a little water and recommended the manifold/riser replacement. Engine did run fine for rest of the summer and oil was just black..not milky..when I changed it just before haulout last fall.

I'm hoping to tackle this in a month or so...before she gets put in the water. Or should I wait until it does get put in the water..and then run the engines to warm them up? I read warming them up can help with those bolts coming free. (less chance of snapping a bolt in the block!)

Wish I had better pics of the engine bay. My year/model..it's tight in there!

Look around locally and on the internet for the best deal on OEM Mercruiser E coated kits that include the gaskets and new bolts.
The manifold bolts are pretty beefy and rarely snap on you.
Great time to replace the spark plugs. Plug wires too if they need replacement.
Pretty easy job if you plan it out right. Do one complete engine before moving to the next in case you forget how something attaches.
Take parts off, and put it back together the same way it came apart.
Drain the manifolds.
I found it easier on my old boat to remove the risers/elbows first from the manifold, loosen the clamp for the exhaust, and twist them out of the exhaust hose.
They’ll be more than one style gasket for in between the manifold and riser/elbow in the new gasket box. They include styles for wet and dry joint exhausts to cover all bases. Just make sure you use the exact same style new one as was on there before.
Tip to make installing the new (heavy) manifold easier:
Either cut the head off one of the old manifold bolts, or get a piece of threaded rod. Loosely thread the bolt with the cut off head (or threaded rod) in the hole on one end just a few turns. Preferable the end that will give you enough room. Don’t thread it in all the way or you won’t be able to back it out when the time comes!
Hang the gasket and new manifold on that loosely installed bolt or rod and use it to support the heavy manifold while you line up the gasket and manifold and start a new bolt on the other end. Get the other bolts started, then remove the headless bolt or threaded rod and replace it with a new bolt.
 
"E Coat"...specifically what is that?

Do people have recommendations for sources for me to purchase the whole kit? (I'm in CT).
I'm looking for a total kit...gaskets, bolts, whatever is needed...to replace both manifolds and risers.

There seems to be what I'd call a "spacer block" between the riser and the manifold also.

How much cooling fluid is in there? Guessing they're drained from that hose on the bottom of each manifold? Wondering how much I should expect to drain out, so I'm prepared....I'd rather avoid having a few gallons of antifreeze pour into the bilge. And I probably don't have much room for a bucket under there either.
 
Hard to say how much coolant will come out. Probably easier to just put a bucket on the ground under the garboard drain.

If you don’t have much room between the motors, it may be easier to do both inboard facing manifolds at the same time. Once one is removed, there will be plenty of room to do the other. That way, you only have one to reinstall with the tight confines.

1. Remove port inboard manifold
2. Remove starboard inboard manifold
3. Install starboard inboard manifold
4. Install port inboard manifold
 

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