496 Poppin through exhaust
 

I recently had a new 375 horse 496 installed in my Velocity, it has about 16 hours on it, I'm getting a popping out of the port side exhaust, predominately over 1500 rpm. It sounds like a misfire of some sort, any idea where to start looking?
Thanks in advance!!

Compression test. stuck valve?

Are you getting any alarms? I'd start by getting it scanned.

Is it under warranty?

Firing order? Might not throw an alarm.Crank sensor maybe how does it run when its not doing it if it runs good doubt its internal but it needs to go on a scanner ASAP the laptop program is better.

Fixx
 

could be a broken rocker arm or a bent push rod..

Simple things first, make sure the plug wires are on the correct cylinders on that side. If plug wiring is right check under the valve cover for as someone else said a bent pushrod or rocker arm issue. If that does not do it , check the compression of the cylinders on that side and see if ones way down, indicating a stuck or bent exhaust valve.
Hope its something simple.

Best Regards,
Ray @ Raylar

Bad plugs, Carbs set wrong or dirty. Or even bad gas from sitting

Cracked spark plug. Replace the plugs, see if it goes away. Went through the same thing on my dads 496.

Thanks guys!!
To answer some questions I haven't gotten any alarms. It seems to run okay at higher rpms but not perfect. There is no warranty on the engine, and the shop that did it is about an hour and a half away and honestly left a bad taste in my mouth so rather bring it elsewhere or fix myself. Learned alotta lessons on this engine replacement.

oh and what is the order the plug wires should be in? Thanks again!!

Easy to determine as the coil packs mount on the valve covers.

Okay after some of me messin wit it and finally bringing it to a mechanic, we eliminated the possibility of it being an ignition problem.... he believes it to be a mal-adjusted valve, as the rockers were replaced when the engine was done.... Thanks for the input and i'll let you know if that is the final conclusion...

valves/rockers are not adjustable on a 496,I believe they get torque to 25lbs.

it does have 2 different length push rods for exhaust and intake,maybe you got those mixed.

1,8,4,3,6,5,7,2

496 Is 1-8-7-2-6-5-4-3,,,1357 IS PORT,,,2468 STARBORD

Joe, what did you find?

If you need anything feel free to reach out to me.

Crazy suggestion but check for a valve cover oil leak.. I've seen oil leak on ignition wires and cause either a pop in the exhaust or thru the intake. Another thing, is broke/weak valve springs can cause a pop... Broken plug will do it, so will a fouled spark plug...especially if an injector is leaking...or a valve hanging up..or even a hammered exhaust seat.

Is the engine turning up the proper RPMS?

In situations like this I've always found you need two people on the boat.. One person to drive, the other to check for symptoms.

Frank

For an update we ruled out ignition and anything with the rockers being installed incorrectly... Also did a compression test and that was fine, A friend is suggesting valve springs, or a bad lifter... The spring seems to make sense so that will be my next attempt

Frank, I may give you a call later in the week, Thanks!!

Do yourself a favor and install new spark plugs first and try it before you go digging into the engine, Also run the engine at dark and look for a light show, Even under the coils.

Good luck with it.

my 496,s where doing the same thing one spark plug was bad and the iac motor took a **** .

It was a fuel injector!!! Found it on this post!
http://www.offshoreonly.com/forums/d...ers-fyi-2.html

What a relief!!!

:cheer:

Install new plugs, add methel hydrate to the fuel to get any water out of the system.

And change your water fuel separator filter.

These have saved me in the past.

http://www.offshoreonly.com/forums/g...ome-ideas.html

definetley plugs dont put cheap one in it though. had this prblem in my old baja h2x single 496 mag, and just recently in my 36 outlaw twin ho's just put new plugs in it and it went away

So this started up all over again on the port side, swapped out the same injector that was the culprit last time and all the plugs and fuel filters, and had no improvement, actually the starboard side started doing the same thing, checked spark on all cylinders, did a compression check again, to see if I broke anything, then had it plugged in to a laptop, the program says I'm at 100% power, HA!!! So I sent all the injectors, 8 and 2 "spares" out to be tested and apparently cleaned. While shipping I realized that at $150 a piece, that was a $1500 box :angry-smiley-038: I sure hope this works.
Had to vent and if anyone else is having this type of problem I figured I would keep you posted on my progress.

Wow thats a a lot of $$ for a test ,how much are they new for a set of 8 ? keep us posted on the outcome , i read all the 496 probs/and fixes and try and store as much imfo as i can on thes motors just in case it happens to me , i want to be ready , some very clever and helpfull people on this site ,its great .

000joe:

I assume you are still discussing that your 496 engine is popping out the exhaust, or is it just a bad misfire that is something you are hearing out the exhaust when a particular cylinder does not fire like the others.
Usually injectors don't cause popping out the exhaust and a cylinder that dropping out does not make a popping noise as no cylinder pressure has built in that cylinder unless it fires.

Late injector timing could cause exhaust popping but that's pretty unlikely in this engine with its controls.

Is the engine performing with a power loss? Or is it just a noise?

You mentioned that some mechanical mods or redo's were done to the engine, could you describe those in detail as there may be issues with that work?

Best Regards,
Ray @ Raylar

Sounds like a bad plug, causing a misfire. I would change those first before anything.

I apologize, their about $150 each new, the box was worth $1500, it's $25 a piece to flow test and service them

it is a back fire, I believe, through the exhaust, it started on the port side and then on the starboard side. the engine was replaced last year and I had the same problem on the port side, replaced the last injector on that side and it ran perfect. The engine is stock. I checked spark on all cylinders, as did a mechanic and he used a lap top to check whatever. the motor has an extreme loss of power, and would only reach 3800 rpm. the only work that was done after the initial replacement was by me, oil changes, an injector, and traditional diagnostic, pulling plug wires, disconnected coils, to try to isolate the problem. I actually spoke to you when I was buying my engine Ray, your always a great source of info on these motors, thank you!!

changed all the plugs


thanks for all the responses guys!! :drink:

Did you try wires?

The wires look perfect and when checking spark, I checked at the plug.....

Figured I would update incase anyone has :drink:a similar problem. Sent the injectors, and two old ones to marren fuel injection, in Ct, had them back within a week, found 4 were performing terrible all were dirty, serviced and sent back, I reinstalled last night and changed BOTH (thought there was only one) filters, and went out tonight for a quick blast, boat ran perfect cruised at 46mph at 3500 and touched 64 w.o.t. without staying in it.