43l 190 hp Exhaust Manifolds

"I lost my first motor to exha

"I lost my first motor to exhaust manifolds failing. I repowered in 2001 with my 4.3l 190hp.
I had to replace my starter after the second season and in removing the exhaust to better access, I noticed the starboard side manifold begining to fail. I replaced both manifolds.
My question (since I am now 2 seasons on the replaced manifolds) - should I change every two seasons based on the original manifolds? What is a good life expectancy for manifolds on this engine with average to moderate use each season in salt water.
I just ordered a new set of manifolds and now wonder if I should try to stretch another season out of the ones on the boat (would be the third season). Any way to test other than to visually inspect for rust indications on the engine exhaust portion of the inside of the manifolds?
Manifolds, elbows, risers, etc. are expensive, but far short of what it cost to replace the motor.
Appreciate any thoughts or ideas!
Mike"

"Mike,

Are you sure the ori

"Mike,

Are you sure the original manifolds were bad, or were you just experiencing the result of a leaking gasket? Two years is a very short life, even in salt water.

I would remove the elbows and have a looksee. You should replace the gaskets by now anyway and this is a good oppurtunity to inspect manifolds from the inside. Make sure you remove the elbow drain plug first. You don't want your inspection results tainted by water from the removal of the elbow.

If at this point you feel they are in need of replacing, well, there you go.

Good luck
Rick"

"I'll bet they are Mercrui

"I'll bet they are Mercruiser manifolds, right?

Jeff

PS: Please answer--I have a bet going on this."

This is exactly why I like fil

This is exactly why I like filling the exhaust mainifolds and engine block with coolant at winter. It helps control the corrosion. Most folks don't want to pay a little extra to do this but its worth it and recomended by Merc.

"Really appreciate the convers

"Really appreciate the conversation...
Rick: I never really thought about just gaskets when I replaced the original manifolds, I just remember being 4 miles out to sea (off Kodiak Island, ALaska)in late October when I lost my engine to exhaust manifold failure - was a cold long ride home on my 15hp kicker. I will have to remove the starboard side to clean up my starter - really hard to get to in my 24' Bayliner Trophy Offshore. I'll inspect the inside of the manifold at that time - thanks for the suggestion. Are you saying I if I see indications of rust on the inside of the manifold, I should trace it to see if it is coming from the gasket? The riser gasket, or the manifold gasket?
Jeff: The original manifolds on the new motor were Mercruiser. If I could cancel what I ordered (Mercruiser), what would you replace with?
Harves: I love my boat and the things it let's my wife and I do. I ended up building a building sized heated shop to store the boat in during the off season (a boat garage). I flush the motor with fresh water and drain the manifolds before storing in the garage - would you still recomend running coolant through the manifolds when I keep it in a heated condition? I should mention I have a closed coolant system.
I'll be pulling the manifold soon to access the starter and will share what I see then.
What is the safe life expectancy for exhaust manifolds on my 4.3l running in salt water?
I really appreciate the conversation here."

"Mike,

The gasket that coul

"Mike,

The gasket that could cause this kind of problem would be the riser to manifold gasket. The raw water circulates through the manifold and exits through the riser. A leak in this gasket could allow that water to enter the manifold. A leak at the manifold to head gasket would only produce an exhaust leak since no water circulates through that area. Regarding life expectency, even neglected manifolds should last 4 years, probably longer. A set that is maintained properly should last 6-8 years, much longer in fresh water.

You might want to see if Mercruiser has a kit to convert your manifolds to FWC. Crusader has done this for years but Mercruiser got away from it some years back. This may be a simple plumbing job which would seriously extend your manifold life.

Good luck
Rick"

"I win! (Knew they were M

"I win! (Knew they were Mercrusier manifolds.) If you think you are the only one loosing exhaust manifolds and engines due to THEIR crummy products, read articles on engines in the below website. (Look for articles on engine failures--take the time to find them. It'll be worth it.)

http://www.yachtsurvey.com/articleslist.htm


Jeff

PS: Anything but Mercruiser is going to be better!"

"Interesting thoughts. I have

"Interesting thoughts. I have a 4.3l and have replaced both of the exhaust manifolds, with rust thru. I used Osco parts. Are these better or worse than Merc?

Jeff good article on risers. Mine are Fresh water only. They looked good when I replaced the last manifold 5 months ago. but the engine and risers are 14 years old, all fresh water only use. Should I change out the risers on time only??/ risks sound bad.
BEAR"

"Alright guys,
I pulled the p

"Alright guys,
I pulled the port side riser to take a look.
I took a photo to post here, but cannot get the file size low enough to post.
In the exhaust portion of the manifold, there are some beaded rust spots, but they don't "appear" to look like leakage, but more like condensation spots. Think I should just clean, install new gaskets and take a look mid season?
I can e-mail the photo's to anyone if they would want to take a look.
Thanks for all the help."

"Pressure test the manifold wh

"Pressure test the manifold while the riser is off. You don't have to remove a exhaust manifold to test it. Make a clean flat plate with the four holes of the riser to block off the water passages. Mine is 1/2 aluminum. Spot the holes off the riser. You can cut a large opening in the middle so you can see/hear a potential leak. Use a new gasket and perfect seal and bolt down the plate. The perfect seal does not harden or cure so you can use the gasket when you are finished. Use the end of the water hose that comes off the bottom of the manifold to install a plug with a nipple you can charge the manifold with compressed air. It should hold and not leak. Make sure the metal around the cooling passages are not rounded over or the surface integrity is bad, you may need to take the manifold and riser to a engine machine shop and have them flaten/surface that area. Most engine machine shops have horizontal belt sanders for flatening all kinds of castings. Yes Im with Rick with the Fresh water cooling of the exhaust. If not I believe that during storage, filling the manifolds until antifreeze trickles out the riser vent is the way to go. I know you flush them but they are rotting sitting, the antifreeze will give you corrosion control during that time. I don't believe that the OEM parts are junk, I do like the stainless riser idea though. Forward pics: [email protected]"

"Anything is better than Mercr

"Anything is better than Mercruiser, though some might disagree.

I too have very old risers that need to at least be looked at. The manifolds (at least on Chryslers) seem to go long before the risers, but---

Jeff"

"Mike,
Most likely what you s

"Mike,
Most likely what you see is indeed condensation. With RWC manifolds the manifolds cool much faster upon shutdown than do FWC ones. This cooler manifold creates an environment where moisture in the exhaust system condenses on the cooler metal of the manifold. This condition is especially noticable in systems with riser extentions installed. This is the reason many manufacturers now include the manifolds as part of the closed cooling system. Crusader's 6.0 engines have FWC risers as well and partially due to this reason, Crusader no longer offers raw water cooled engines and have not for several years now. The coolant in the 6.0 circulates through the riser. There is a discharge port which expels the raw water and helps cool the exhaust. They have also started to use collector plates or "turbulators" as Mercruiser calles them. These plates are simply a SS plate similar to a block-off plate, but the inside hole is smaller than the exhaust passage in the manifold. This extra metal is formed in the shape of a gutter. The purpose of this is to collect condensation and keep it from running down and into an open cylinder. It doesn't hold much water, but then again, it doesn't take much water to damage your engine.

You should consider installing these turbulators in your system when you reassemble it. They aren't very expensive and could eliminate much of your problem.

Good luck.
Rick"