2001 4.3 liter mercruiser flame arrestor

[donnyskz1]

ARRESTOR


Need help in trying to figure out what would cause so much heat to burn the flame arrestor. We took the boat one day for about 3 hours and the boat ran perfect. We took the boat out the next day and after about 30 minutes the alarm came on. I opened the engine cover it was full of light gray smoke. When the smoke cleared I could see the flame arrestor was messed up. There was smoke coming through the arrestor. The gauges on the boat never showed the engine was not over heating. After I let the engine cool for about 30 minutes we were able to idle back to the dock. There is now a tapping not quite a knock coming from the left side of the engine. It sounds like it is coming from under the valve cover. I just had the manifolds and risers changed about 2 weeks ago. I don't that would cause the issue. I am trying to post of the video of the engine running with the smoke coming out of the arrestor but am not having

 

[Scott Danforth]

you overheated the carp out of your motor. to get that hot you may have even had a fire.

the tapping and knocking is because you probably burned up the pistons and you most likely melted the exhaust hoses and burned up the flappers.

when was the last time you changed the impeller?

 

[AShipShow]

Holy crap! I don't think I've ever seen that bad of an overheat. I agree with Scott, that almost seems like there was a fire.

 

[donnyskz1]

The impeller was changed about 2 months ago when I had the boat serviced. They changed the impellor, rebuilt the carb, replaced the bellows and changed the gear oil and a couple of other minor things done.

 

[bman440440]

to me that looks like he had a BIG back fire through the carb... that's the 1st thing that I thought we I looked at the pic

 

[Scott Danforth]

Hey Bondo , achris kenny nunez , muc , any of you see anything like this? if it was a backfire, it was a dooozzzy.

 

[harringtondav]

My pre-retirement employer gave me many hours of problem solving/root cause analysis training.

One of the first questions is "what changed". That rebuilt carb waves a big flag.

 

[donnyskz1]

I don't normally run the boat hard. I normally keep it about 30 to 35. When this happened I did go to WOT and was running like that about 4 or 5 minutes when the alarm came on. What ever has caused the problem fortunately the alarm sounded and I shut it down before the fire extinguisher could have gone off. The water temp on the boat showed the whole time between 130 and 150. So far I have only checked the oil in the motor and there is no water in the oil. I did notice a oil residue on the inside of the carb.

 

[achris]

.... That rebuilt carb waves a big flag.

That was also my first thought reading though the first reply post....

The 'ticking' could be an intake valve, pushing air/fuel back up through the carb and causing the 'fire'?

I'd be pulling the carb and checking all the settings.

Also, your mechanic did you no favours when he replaced manifolds and elbows. When replacing both at the same time, you ALWAYS upgrade to dry-joint!

Chris.......

 

[Bondo]

Hey Bondo , achris kenny nunez , muc , any of you see anything like this? if it was a backfire, it was a dooozzzy.

Nope,...... No doubt a doozy,....

 

[muc]

Don’t think there was a fire. The crankcase breather hoses don’t look melted.
I’ve seen flame arrestors that were damaged by backfire or heat and they didn’t look like this one.
Mystery to me.
Wonder what happened to the plastic cover that’s missing? Also looks like somebody has over tightened the nut.

 

[QBhoy]

Doesn’t look like it’s been extreme heat that’s done this. Other things would be toast too. Looks like a serious detonation from the carb, possibly aided by a flooded manifold ??

 

[Bt Doctur]

a backfire/detonation is my guess. takes a lot to blow one apart. Sometimes fuel in the oil will cause a crankcase explosion.
May have detonated a piston so its time for a compression test.
last one I heard about in a gm motor blew the valve covers off the motor

 

[donnyskz1]

Got a call from the shop this evening. They still cant figure out what caused the arrestor to come apart like that. They did compression check and said number 2 cylinder had 30 PSI. They removed the head and said the number 2 piston had small pieces missing and there is bad scaring in the cylinder wall. The motor is not repairable. I am going to see it tomorrow. It would be about 6800 for new motor and installation.

 

[donnyskz1]

They said about 3000 for the motor and the rest is labor. I did some searching and I can get a long block for about 2300. I have never swapped out a stern drive motor before. Not sure how complicated it would be. I have done lots of car engines and outboards before. I would think I could do the swap myself but not sure.

 

[muc]

They said about 3000 for the motor and the rest is labor. I did some searching and I can get a long block for about 2300. I have never swapped out a stern drive motor before. Not sure how complicated it would be. I have done lots of car engines and outboards before. I would think I could do the swap myself but not sure.

Easier than a car, harder than an outboard.

 

[harringtondav]

I fretted over my first engine pull before I did it. Not a bad job at all. Stating the obvious - get to the root of the likely fuel leak before you touch off your new engine. My first guess is a problem with the float/needle/seat allowing raw fuel to spill into the manifold.

 

[Scott Danforth]

They said about 3000 for the motor and the rest is labor. I did some searching and I can get a long block for about 2300. I have never swapped out a stern drive motor before. Not sure how complicated it would be. I have done lots of car engines and outboards before. I would think I could do the swap myself but not sure.

R&R'ing a motor is a 1 day job including stripping down the one motor and building up the next. an hour to get the old one out, 3 hours of swapping parts, eating sandwiches and drinking beer, an hour to get the new motor in, and a bunch of breaks with beer.

pull drive
disconnect exhaust hoses
disconnect fuel line
disconnect harness
disconnect battery cables
unbolt front mounts
unbolt rear mounts
lift motor out

 

[donnyskz1]

I went to check out the motor today. Definite bad scaring in number 2 cylinder. I will be changing the motor. I asked them if they good put everything back together so when I do the engine swap I can take pictures of how everything is supposed to look when I put it back together. While I was there it did not seem like it would be to difficult to get it out. I am guessing I will have to get a new outdrive gasket kit and new exhaust manifold gasket kit before it can be put back together. I know I will need an engine alignment tool as well. Since the bellows were changed would I have to change them again once the outdrive is out? Should I change the gimble bearing while the outdrive is out? Should I consider changing the flywheel while the motor is out? I know that is the only to change the flywheel while the motor is out.

 

[Scott Danforth]

they will charge you to put it back. boats are not that hard, and if you understand righty-tighty / lefty-loosy and you have worked on a car yourself without needing to go to youtube, then you will be fine.

you need to pull the drive every year for inspection. if the bellows were just changed, they will be good for a few years.

no need to change the flywheel unless you broke it. if the ring gear is bad, simply change the ring gear ($15 part). the cast iron wont wear out.....ever.... so why would you ever want to change it unless you have $80 in your wallet you want to spend.