Broken exhaust flapper just locked up new 5.7

[BajabossJD]

Hey guys,

A few weeks ago you all were helpful with a question on had while working on a friends boat. I installed a new 5.7 carb motor in place of a low compression 5.0 he had. I completed the job, installed all new exhaust with 3" spacers (dry joint). Boat ran great on the Sea Trial. Fast forward a week and customer takes it out.. Calls me saying its running rough and wouldn't restart after he got fuel. He said it cranked and cranked but wouldn't start.

I get it back in the shop and the dreaded spinning of the starter happened. I pulled started and plugs and tried to turn the engine over with studs on the balancer. Wouldn't move. I pulled the exhaust and saw a mess of Salt water in one manifold. I moved further down and saw this pic of the broken flapper.

I pulled the head and saw water in the cylinders. Removed the water, poured atf / acetone in each cylinder. Its been a day so far and the engine is still locked.

It was exactly one week since he said it wouldn't start ( I was out of town over the 4th).

At this point, I'm better off trying to hone the block and install new bearings and rings. Maybe the block will free up with another day or two of soaking?

This was a remanned long block by a reputable builder in Florida. Not his fault at all. Since I'm on the hook for this job... am I better off buying another long block or rebuilding the current unit that has maybe 3 hours on it? Hone block, clean up the head, install new Rings and bearings.. I have a few new completed gasket kits in stock.

Here's the pics. Bad luck for sure and this job continues to occupy my shop. My fault for not checking flappers. I was told all that stuff was new. I'll take ownership of it but I'd like to know if rebuilding the fresh block is smarter than dropping another $2k on a long block. These pics are 1 week after the failure, Salt water and 100 degree Florida temps... Ole' Iron doesn't like it.

I've rebuilt a few four strokes before ( mostly BRP and Yamaha Ski motors ) but never a hydro locked one.

Thanks,
Joe

 

[Rick Stephens]

I'd pull it down and rebuild it.... in fact, I did just that. Had to rebore and replace brand new pistons and rings. Was able to reuse original bearings even.

 

[achris]

With 3" risers in the exhaust the only way water will have gotten into the cylinders is if the customer pulled a 'hard stop' (was on the plane and just pulled it back to idle and shut it down.) I'd be quizzing the customer a lot harder. I ran my old 165 with the shutter missing for the entire 8 years I owned it. Never once got water in the manifold... But then I also never pulled hard stops...

Being a new engine, doing that constitutes abuse...

Chris..

 

[poconojoe]

I can see how you may feel obligated, but I agree with Chris. That had to be an abusive move, no doubt. A hard stop... that's just something you should never do, exhaust shutters or not.

Hey, maybe the hard stop caused the shutter to break. But, you're caught in the middle. Maybe you can explain to the owner exactly what he/she did was just plain wrong. Maybe share the cost, but it's really not your fault. Tough one indeed...

 

[Scott Danforth]

or the boat was overloaded.... what is the distance between the elbows and the SWL?

 

[tank1949]

It's water over damn now, but I have known people who were able to fill motors with diesel oil until they could work on them. Salt water and Iron don't play well together. Unfortunately, you are the one that customer paid for job. In his mind, if you don't make him happy, he may and will spread it all over FB or WWW. I don't see how you could have assembled and installed a 350, including manifolds and risers and bellows w/o noticing damaged or missing flappers. However, I wasn't there. You may try to narrow him down for more details and perhaps agree to split expenses after you show him flapper that he said was new. It doesn't appear to be new.

 

[Searay205]

A boat owner cannot rapidly pull the throttle from wide open to neutral? I have never seen that in any owners manual maybe I missed it. Glad i read this post I will quit doing it. If the engine is running wouldn't exhaust pressure keep water from back flowing. What about when backing up? Why wouldn't water back up in that situation. I am confused as to how water can back up with engine running.

 

[achris]

You missed 2 words 'and shutdown'. See plenty of idiots doing it locally... Mostly to pick up skiers. They run you to them, and shut the key off as they pull it into neutral. :facepalm:

 

[Searay205]

Who could be that stupid and be able to put a boat on trailer....

 

[tank1949]

A boat owner cannot rapidly pull the throttle from wide open to neutral? I have never seen that in any owners manual maybe I missed it. Glad i read this post I will quit doing it. If the engine is running wouldn't exhaust pressure keep water from back flowing. What about when backing up? Why wouldn't water back up in that situation. I am confused as to how water can back up with engine running.

UR not confused. Good questions. I have back down hard fighting a blue marlin but I never shut off motor. I never sucked sea water either and I don't recall having shutters installed on Alphas at the time. I do now! I did experience hydro lock after head cancered and sucked in sea water.

 

[Lou C]

The problem with doing this is not just the throttle position, its the force of the water pushing against the transom as the boat drops off plane. That can exert enough pressure to push water up the Y pipe where hopefully it gets stopped by the flappers.
Which leads me to a question especially in view of Volvo's recommendation to remove flappers from the Y pipes of their I/Os back in the late '90s:
would it not be better to use an inboard style flapper over the exhaust opening in the gimble housing in place of the exhaust bellows or tube, since this could stop water from getting pushed up the Y pipe in the first place? Since this probably would have been cheaper than a pair of flappers in the Y pipe, my guess is Mercruiser would have done that if it was as good or better. Unless not having the bellows would lead to too much noise.

I wondered about this when people with Volvos have asked about following that TSB to remove the flappers (and later production Y pipes were not even drilled for the pins to install them even if you wanted to...
thoughts?

 

[Searay205]

I had exhaust flappers in my last boat, they rattled for 15 years at idle. I assume they are in my current boat. I know if I slow down fast not only does a wave of water come over the swim deck it crawls up the back of the boat and sometimes dumps into the engine compartment ventilation openings. Why they didn't put the vents on the side of the haul like my last boat is beyond me. Its actually forced me to slow down slow so I don't drench my trip pump with saltwater. Already replaced trim bracket with stainless as the carbon steel was rotting away.

I have no doubt if i was on plane and rammed in neutral and shut engine off water would hammer back towards engine hopefully shutters are installed...

 

[havoc_squad]

Here's the pics. Bad luck for sure and this job continues to occupy my shop. My fault for not checking flappers. I was told all that stuff was new.

That's why many of the local shops around my area that actually do engine/powerhead work won't do any work without written quote approved in writing of agreeing to replace/verify all wear parts part of the drive system that could result in pre-mature engine failure.

New engine block water pump, sea/raw water pump rebuild, exhaust flappers, etc.

If a customer doesn't want to accept those terms, the shops have every right to respectfully tell that customer go somewhere else or buy a new engine where the labor is warrantied by the manufacturer in case it fails because of product defect and not abuse.

There are too many bad apples now that run their stuff hard and abuse it badly, then come back and demand you fix their screwups for free.

 

[JustJason]

The flappers, or lack there of, had nothing to due with the water getting into the engine. If this was a Volvo 5.7 instead of a Mercruiser 5.7, there wouldn't even be flappers. You could have a static water line issue, as Chris mentioned. Or you could have had a gasket issue, mating surfaces not being flat, incorrect assembly or a couple of other things happen, but it wasn't caused by any sort of flapper issue.

 

[tank1949]

The flappers, or lack there of, had nothing to due with the water getting into the engine. If this was a Volvo 5.7 instead of a Mercruiser 5.7, there wouldn't even be flappers. You could have a static water line issue, as Chris mentioned. Or you could have had a gasket issue, mating surfaces not being flat, incorrect assembly or a couple of other things happen, but it wasn't caused by any sort of flapper issue.

Then why have them in the first place if they don't help and can break off and cause overheating? Which gasket could fail to cause this? I prefer external transom mounted flappers but they are LOUD and retrofitting may also be a pain on a MC.THX

 

[BajabossJD]

Thanks for all the input. The dry joint manifolds, risers and spacers were brand new. Long block was assembled by engine builder and spotless. I dressed the engine, installed it back in boat and out everything back together. Is it common for dry joint manifolds to leak internally as the old wet joint units do? It’s interesting to see the different opinion on the flappers. I just received them and I’ll be installing them before I reinstall this engine again.

I also appreciate the tip on what the other shops do in regards to wearable items. There has to be some stop point when working on someone else’s boat.. slippery slope on what they can / want to blame me for. I’ll try to turn engine over tomorrow to see if it’s free. If not, I’ll pull it out on Tuesday and start tearing it down.

Any other ideas on mechanical failures / incorrectly installed components that could have caused failure this so fast? I’d like to learn from any mistakes.

 

[achris]

Never seen a dry joint manifold gasket failure. I have however, seen a crack manifold. I also noted on the diagnotics that the engine had at one point been hot (code set in the ECU), and on further questioning the owner admitted they'd pick up a lot of weed and the alarm did go off. He said they just trimmed the motor up, cleared the weed and restarted the motor. I suspect, and the owner was ok with it, that the manifold had gotten very hot, all the water had boiled away, and once new cold water came in, the thermal shock is what cracked the manifold.

The thing you'll notice about the dry joint gaskets is they are 'turbulators'. That lip around the edge of the exhaust passage gets red hot in the presence of exhaust gas, and any water that does get past the shutters, usually is boiled off immediately. For the volume of water that was need to do the damage you appear to have, looking more and more like abuse to me....

Chris........

 

[kccoe]

Not your fault several things could had gone wrong on the water ...I had a impeller pump failed while getting up on plane ...my first mistake was not paying attention to temp gauge as we idle out . Second mistake Right as I got plane overheat alarm sounded and I came off plane too fast but I did not stop engine . 3rd mistake I Noticed a slight louder header type exhaust sound . I was now as idle and cooling down and I noticed my wife hand reach for the key switch as the alarm was screaming ...I shouted don’t kill the engine * She turned the engine off just as I was screaming don’t ....flapper failure Over heat melted all the rubber off , found pieces in the out drive exhaust boot .5.7 MerCruiser efi bravo 3 Hydro lock in all cyclinders who knows what the rods look like pull plugs and drain water Out of cylinders and spray wd40 drain that ..have not tried to restart myself . Take it in to compression test cylinders and hope for the best but doubt I got lucky