anyone ever change an exhaust maifold?

[CATCH AND EAT]

Bayliner Trophy 23', 4.3 L Mercruiser. Looks like I have a bad manifold. It's burning spark plug wires because the manifold is getting to hot from a possible obstruction from within. Does not look like a huge job but I am not necessarily a mechanic. Anyone ever have to do this on their boat?

[Captn]

C&E, I know exactly what the matter is as does John (Pilar) and Krystalflash. There is a baffle inside that acts to keep the manifold from cooling too fast. That baffle has broken loose and is obstructing your outflow. You must remove the motor and put a new exhaust manifold on with the new and improved baffles. If you know what you are doing it will take about 2 days, It took me 5 weeks. Now ours motor is a 350 ci Chevy, the 4.3 is a six cyl, and perhaps it can be repaired without removing the motor (I think that is wishful thinking). I am refering to the exhaust bull horns, not the manifold it self, sorry about the confusion.

If you run with the baffle loose, then you may have the same problem that we had. The baffle rattled until it broke a hole in the exhaust bullhorn, and then we had sea water squirting into the boat, at kind of a bad time though, as we were 32 mile out at the chicken ranch. Got a chance to find out how professional and helpful the Coast Guard was as we were towed back to Newport.

What year is your Trophy? I think ours is an '88 and the same size as yours.

[ 07-09-2003, 06:33 AM: Message edited by: captn ]

[Miss B Haven]

C&E - I've done it a few times (on a 350 chev). Not difficult unless the bolts are rusted in place.
Kinda weird that the manifold is getting hot but the engine is not overheating. Do you have raw or freshwater cooling on that thing? If the cooling ports in hte manifold are all crudded up it would overheat the manifolds, but the engine should be running hot as well. :whazzup:

[Miss B Haven]

captn - remove the motor to replace a manifold? I've pulled them on my old boat (Bayliner 24) with a 350. The only reason to pull the motor would be if you couldn't get to the bolts and if you can't get to them you probably couldn't change a spark plug either. :whazzup: :depressed:

[Pilar]

Not on that motor. Call Sea-way marine in Seattle and obtain the parts before you mess with it. You can get them at a local marina but Seaway will have the best prices and they offer Barr, an aftermarket unit that wil bolt up just like the originals for less money. I installed a Barr manifold on 'Pilar' and had to pitch my prop up one notch because of the increase in engine power. That old manifold had been acid flushed 3 otr 4 times and was done. Also make sure you have a good water pump impeller and no other issues before you jump.

Get the parts before you tear it down! Otherwise you may be waiting for parts with the engine in pieces. I would change both sides at the same time for additional peace of mind.

This is also a good time to go to stainless bolts and hardware. The only issue you might ave in this otherwise simple repair is stuck bolts. Stainless hardware with antiseize compound will eliminate the stuck bolt problem. Any bolt that will not turn just heat them with a propane torch till they smoke and try again. Breaking a bolt off means pulling the motor in many cases, so be careful.

Once you get the manifolds off check the water passages for loose scale and blockage. If it is not too bad you can clean the manifolds with muriatic acid. The acid can be purchased at a pool supply store or Home Depot. Use a metal rod (brass brazing stock works great) to ream the holes and passages in the manifold you can get to and tap the manifold with a hammer to loosen rust and scale. Make sure you shake anything you knock loose out on the ground.

Then block all the water passages except the ones where the risers bolt on. Plywood and silicone sealer work good for this tempaorary blockage. Cut covers out of plywood and glue them on and bolt them over the water holes using the mounting bolts and some plain nuts. Pour in Muriatic acid until full and allow to sit 1 hour. Wear heavy rubber gloves and a face shield when handling the acid.

Dump out the acid and flush hard with water for at least 1/2 hour. While flushing, beat on the manifold with a hammer, ream with the brass rod and shake the rust loose again.

Most castings are thick enough to endure this procedure at least once. Who knows it might save you the $500 for a pair of new ones. If the acid eats a hole in the manifold you have lost nothing because you were going to buy new anyway.

One last note. Pressure test the system and check for leaks once you get it back together. 10 lbs pressure should cause no leaks, anywhere.

Good Luck

[CATCH AND EAT]

It is a 4.3l mercruiser. No need it appears to remove the motor. Just got to take the boat out of the water. :grin: Block temp remains at 190 degress and no rattles in the manifold at all. Just a hot manifold.

[Miss B Haven]

C&E- On my 2452 CD you could do it in the water (and I did once). Kinda scary but the flapper in the exhaust (just below the elbow that you will probably need to pull to get the riser off) is about 2 inches above the water line then the pipes another 2 inches high. I had 4 inches to spare before the boat woulda filled with water. :shocked:

[finclipped]

I have replaced the manifolds on a GM 327. As long as the bolts come out and the clamps come off, its not a difficult process. New manifolds don't need any "rust" cleaning, but I would recommend removing them every so often and doing what Pilar said about "acid washing" or go to a machine shop and have them glass-beaded. I did it to mine, and it does a great job of removing rust and unclogging passages. Glass beading is similar to sand blasting, except they use small glass beads instead of sand. It really cleans things up.

Since it is GM V6, I would assume you have an exhaust manifold on each side.

What I have noticed, is that when a manifold overheats, it is because a passage is blocked by large flakes of rust (or something else). Remove the blockage and the water will flow again and cool the exhaust manifold. The water has different paths it can travel, so its possible to have the motor operate at normal temperature (190), even though one part of the manifold is heating up. The water will find an alternative path until all passages are blocked by rust flakes. Its a tough environment and eventually the manifold is too rusted to work any longer.

[KrystalFlash]

I believe that you need to remove the manifolds and check them to see if there is blockage in them. This is most likely the case. You can take them to someone to have them dipped in Muriatic acid or sand blasted or both. It depends on the state that they are in, salvageable or not. I don't think that you need to remove the engine in this case. the manifiolds should be easily removed by using a socket wrench and extension with possibly a breaker bar. Be careful not to break any of the bolts off as this will cause you extra work if you are going to do it yourself. As my good friend Pilar has shown me, it is relatively easy to remove rusted bolts with a torch by heating them to remove them. My suggestion is USE the UTMOST CARE while you are working on this as it can become a huge problem and a lot of work REALLY fast. As Pilar has stated Seaway marine is a great resource for parts. Be sure to contact them if you need any. You will need gaskets and I would even think about changing all of the bolts while you have them off. I would also remove both of them if you are going to do this as the problem will most likely surface with the other manifold soon. Best of luck to you and feel free to contact me if you have any questions.


KF
I'd Rather be Lucky than Good

[Fishplay]

C&E where's the boat at? Your talking pretty simple stuff here. Your engine is basicaly the same thing my sled has except mine is volvo.

If it were the off season you'd have offers of help coming from all directions. But it's TUNA TIME.

If you bring it to me I can start on it Monday and have it done for you Friday night.

I would pull it and check it out first. If it just needs hot tanked I can have it done locally and back together in a couple days.

If it needs replaced I can order new from Sea Way or Doc Freemans. I have an account at Doc's and shipping only takes a couple days so it should be back together by Friday.

Provided I don't run into issues with stuck bolts I'm gussing 2hrs tear down and another 2 reassembling.

fishplay@juno.com

[CATCH AND EAT]

Right now the boat is in Ilwaco Wa port. I am going to have to pull it out of the moorage possibly this weekend and bring her back home. I did talk with Jeff at Chinook Marine in Chinook but he is 2 weeks out right now.

My other issue is my trailer has a few issues to deal with too. I had a couple of brake lines rust in half and did'nt know it until I inspected them after unloading the boat. [img]graemlins/dork.gif[/img] Sure felt stupid when I saw them. Truck stops the big boat just fine but I like the added necessary safety of the trailer breaks. So I guess I will need to improvise for a week or two until I get the trailer fixed and then I'll do the boat. Looking like I'll need to stock up on penitrating oil to break those bolts loose.

Hate this kind of stuff. I spent 2 weeks of evenings going over this boat and I still have major issues. At least it is still early and I should get her going. Certainly a continued learning experience.

Fishplay, thanks for the offer bro. Looks like you are a ways away from me though. Grand Rhonde?

[ 07-09-2003, 07:52 AM: Message edited by: CATCH AND EAT ]

[Bait O' Eggs]

Bernie - Run the boat down to Fishplay and while your in Grande Ronde you can put $100 on black 13 and have enough winings to pay for the repair.

Fishplay might even be able to tell you which machine to stuff full of dollars.

[CATCH AND EAT]

Gee thanks Roy, that was about as much help as a porcupine in a ballon factory. Just what I need to do is throw money at the natives. Money would be better spent on a nice steak dinner with the wife. I never win anyways. Been there done that finished with an empty wallet. Lesson learned. I'd rather be addicted to fishing. Costs about the same though come to think about it. :shocked: