***UPDATE***Check Your Kitty Cats***UPDATE***

[Clutch-n-Throttle]

Last week I posted my high rpm engine fault thread. It went like this...

I have a 2007 VTX 340 Monsoon with 884 hours. I was motoring back to the hotel. I was cruising at 40-41 MPH at about 5000 rpms. I was WOT to maintain that speed. I was cruising along when the engine lost power and I got an "engine fault" on the display. I put it in neutral and the engine felt and sound like a major misfire. There was a small amount of steam coming from the exhaust. The engine temp was 190degs. I turned off the engine and let it sit for a few minutes. Tried to fire up the engine. I took about 3 seconds of cranking until the engine started. There was a clacking noise coming from the #5 or #7 cylinder and the engine ran very rough. I tried to give it some throttle and it would not go over 1000 rpms or 5 MPH. Then I hear and felt a clacking and vibration from the engine. I just turned it off. I checked the fault codes. I got an inactive code of 66014 - Voltage Short or Below Normal Range. I checked the spark plug wires and got good spark to each plug. Check all electrical connections. Nothing. After about 30 minutes, I fired up the motor. It still ran rough with a clacking noise coming from the starboard side cylinders.

Here is an update.

Took my boat to my mechanic on Friday. Started the motor and it was still making a lot of bad noises. We started the diagnosis process. Checked the compression on the cylinders. Zero compression on cylinder #6 and #8. Checked the plug on #8 and this is what I found.


Pulled off the exhaust boots on both exhaust manifolds and found this...


The catalytic converters were missing! I pulled the exhaust/silencer and found a big chunk of cat inside. The majority had blown out the exhaust when my engine died.

My mechanic put me to work and I tore down the interior and engine.


Continuing with the tear down, I removed the even numbered head(port side). This is what I found.

The left cylinder is the #8 and right is #6

#6 cylinder



The heads looked decent and can be rebuilt.

Final analysis.

The cats overheated and blew out. The cats plugged up my exhaust and created instant back pressure on the motor. The #6 and #8 pistons basically melted. I was running on only 6 cylinders which explained the loud clacking noise, vibrations, and what I experience as a heavy misfire.

If you are pushing moderate to high hours on your motor, please check you cats. Inspection of the remaining cylinders showed that the motor was perfectly fine and looked very strong.

Time to find a new motor.

Edited July 20, 2013 by Clutch-n-Throttle

[Pistol Pete]

Man,

That sucks.

[WakingMeHappy]

With >900 hours that stinks. Will your insurance cover it?

Edited July 1, 2013 by WakingMeHappy

[Bawshogg]

I have heard there were issues with the early cats .MAN THAT BLOWS, literally.

[Lance B. Johnson]

Bummer. Looks like a spendy one cause not only do you have to replace short block, you've got the cats as well.

Edited July 1, 2013 by Ruffdog

[WakeGirl]

Is there any reason that he couldn't go sans cats? If it were me, I'd seriously be contemplating that question.

[Bradley Thornton]

Just buy new block and pistons. Great time to learn how to rebuild. You may can even use that block.

[Nitrousbird]

Is there any reason that he couldn't go sans cats? If it were me, I'd seriously be contemplating that question.

Other than perhaps a tuning issue or the need for a few different parts - no. I would be doing the !CATS mod ASAP. And if that meant a reprogram, I'd do an upgraded motor in the process (something Hamerhead-ish as that would be a more direct swap).

[Clutch-n-Throttle]

With >900 hours that stinks. Will your insurance cover it?

Nope. Checked my policy. Does not cover mechanical failures.

Bummer. Looks like a spendy one cause not only do you have to replace short block, you've got the cats as well.

Yep. Might as well.

Is there any reason that he couldn't go sans cats? If it were me, I'd seriously be contemplating that question.

I've thought about that. Don't know about surfing behind a stinky exhaust filled area behind the boat.

Just buy new block and pistons. Great time to learn how to rebuild. You may can even use that block.

That's my intention. I ve a lead on a block with pistons. I can reuse my cam and rebiuld the heads. As for the block, might as well be my back up anchor.

[Clutch-n-Throttle]

Other than perhaps a tuning issue or the need for a few different parts - no. I would be doing the !CATS mod ASAP. And if that meant a reprogram, I'd do an upgraded motor in the process (something Hamerhead-ish as that would be a more direct swap).

What is the "!CATS" mod? The block I'm looking at is 340 Monsoon bored out to about 380. Not quite the Hammerhead but close.

[Lance B. Johnson]

The block you have is just a 5.7 Chevy truck block.

What I would do if it were me: buy a short block. If you tear that thing down to do a rebuild your going to have to wait for machine shop and parts and assembly etc. do this and you could be back on the water in a week or two depending on shipping. Plus hate to say it but you increasing the probability of another failure due to assembly or machine shop error. I'm experienced in engine building and I'd still do it this way. It's faster, simpler, and probably less risky.

If you do buy a short block that isn't directly from indmar I would do some research and see if you need to swap cams. I'd probably just do it.

WG's suggestion- If it were mine, I wouldn't replace the cats But that's me. I doubt a tune would be necessary, but you'd know pretty quick if it did.

I'd skip the hp stuff unless you really need to (footing lots of weight) sounds like a headache to me.

Edited July 2, 2013 by Ruffdog

[Falko]

If you plan to keep the boat, get a ZZ4 short block and go from there.

If you are going to the adventurous route and rebuilding, I have a crank, rods and pistons from a Mercruiser that was in my last boat when I got it, the block had frozen and I replaced it with the ZZ4 short block. Those components I have are simple cast, nothing exotic, but I believe that to be true for the Monsoon engines as well. All low hours, sub 100. You are welcome to those components, just pay shipping. I'll get you info if you are interested.

[jk13]

If the system only has O2 sensors before the cats there would be little to no tuning issues because there is nothing telling the computer of the change to cat less. OBD1 cars are this way.

If there are four sensors (tow pre-cat and two post-cat) you could use O2 simulators in place of the downstreams to get around the tuning issue if you did cat delete. Been used in OBD2 cars for years.

[MalibuKarl]

Anyone know how we would go about checking status of Cats? (short of opening up?). I know in the auto world you can measure temperature with an infrared thermometer. And Clutch - sorry to hear that happened to you with the season beginning. Keep us posted.

[Michigan boarder]

That stinks. Naughty kitty. And not in a good way.

[racer808]

How does one go about seeing if their cats are bad or what?

[Falko]

Unless someone retro fitted them, your 2002 shouldn't have them.

[wakesetter8796]

Cats started on 2007+ monsoons, started on hammerheads in 2008 I believe, and all other engines in 2011

[oceanbu]

Just replaced the ETX/CAT manifolds last year. Up here in Canada they are $1200 a piece! After reading this thread I am thinking of going with HiTek Stainless or Stainless marine and get them to put a recepticle for the O2 sensors on them next time. I run in Saltwater so that is why stainless steel is preferred.

Dude what happened to your motor just makes me sick!

[built2rev]

Damn, man that sucks!!!! Get that thing fixed asap the season is here and it is time to use that thing!!!! Good luck on the engine replacement it is kinda a pia but well worth it when it is all done..

[Molarbu]

I'd keep the CATS if I were you.

[Woodski]

The marine cam is specific, so if you drop in a non marine short block you won't have the same cam as previous. The ZZ4 option is a good one, and I swapped my cam to the ZZ4 cam and really like it, but I basically slalom and barefoot so the power gains at the upper end are a benefit. The ZZ4 cam will give up a slight amount down low so if that is a concern, think carefully on your options. The ZZ4 cam with free breathing intake/exhaust really gets with the program from 1500-4500 rpm. and really shines 2000+.

Can you tell if it took out the head gasket before the pistons went?

[Nitrousbird]

What is the "!CATS" mod? The block I'm looking at is 340 Monsoon bored out to about 380. Not quite the Hammerhead but close.

!CATS = removing the cats.

I sure as hell hope they aren't boring it out to 380ci!!!

Your motor stock is a 4.000" bore and a 3.48" stroke. Your standard rebuild overbore is .030 (so 4.030"), which is a 355ci motor.

To get 380ci on just a bore, you would have to have a .170 overbore! I doubt there is enough material in the cylinder wall of the block to do it without putting a hole in the wall...and if there was enough it would be paper thin and break very shortly.

On that block, the realistic way to get to those cubes would be with a 3.75" crank and .030 overbore (your standard 383ci configuration), or if the block is good enough, a .020 overbore for 381ci, another common configuration. You WILL need a retune going with a longer stroke crank.

Also, if going to a longer stroke crank, I would bypass the 3.75" crank and go straight to the 3.875" crank with the .030 overbore (396ci configuration). The block will already be getting machine work and the additional machine shop work is minimal to clearance the extra stroke, yet you gain 13 extra cubes in the process.

[Clutch-n-Throttle]

Can you tell if it took out the head gasket before the pistons went?

The head gasket was fine.

!CATS = removing the cats.

I sure as hell hope they aren't boring it out to 380ci!!!

Your motor stock is a 4.000" bore and a 3.48" stroke. Your standard rebuild overbore is .030 (so 4.030"), which is a 355ci motor.

To get 380ci on just a bore, you would have to have a .170 overbore! I doubt there is enough material in the cylinder wall of the block to do it without putting a hole in the wall...and if there was enough it would be paper thin and break very shortly.

On that block, the realistic way to get to those cubes would be with a 3.75" crank and .030 overbore (your standard 383ci configuration), or if the block is good enough, a .020 overbore for 381ci, another common configuration. You WILL need a retune going with a longer stroke crank.

Also, if going to a longer stroke crank, I would bypass the 3.75" crank and go straight to the 3.875" crank with the .030 overbore (396ci configuration). The block will already be getting machine work and the additional machine shop work is minimal to clearance the extra stroke, yet you gain 13 extra cubes in the process.

Thanks for the info. I plan on replacing the exhaust manifolds with new CATS. Don't want to surf behind stinky, gassy boat

[Nitrousbird]

The head gasket was fine.

Thanks for the info. I plan on replacing the exhaust manifolds with new CATS. Don't want to surf behind stinky, gassy boat

You will have FAR fewer fumes with an FAE + !CATS than CATS alone. I'm willing to bet the fumes with !CATS + STE tips are similar to CATS and standard flappers. I surf with the STE and don't really notice much in the fumes department.