342 6.2L Running Rich

CrewLounge

Al, 
I have an 02 342 with twin 6.2 engines. This past summer I noticed the engines were continuing to run rich after they warmed up.  Mostly because of the rich smoke.  My mechanic has been working to fix it this winter and has replaced every sensor associated with the ECM, had the injectors checked and cleaned, fuel pressure is 25 psi at the rail, and it is still running rich. Have you had this issue with 6.2's?  My mechanic is in contact with Mercruiser and they are leaning toward an intake gasket leak or internal vacuum leak?  Any ideas?

Handymans342

Whats the vacuum reading?

Michael T

Mercury may well be correct but before I started an engine tear - down I would also look at the fuel pump pressure,  do a compression test of the cylinders, check the spark plug heat range and condition of the spark plugs and wires. BTW are you getting the correct spark? Trying to think of everything LOL. 

Michael T

I assume the "smoke" is fuel related not oil related as a result of worn oil control rings that a compression test would catch.  Your technician can quickly check to see of your intake manifold gasket is the culprit! 

212rowboat

What's your operating temperature?  Swapped 'stats too?  

Intake leak is easy to find with ether.. small blasts around marrying surface and listen to engine for change in rpm... Doubtful this is your issue... I wager its stat related if you've changed everything else and to no avail, or, even easier- your air filter/spark arrestor is clogged.  

Michael T

I agree with Al.  If my memory is correct you should be showing about 45 psi? Even so,  I think there may be a second factor involved  here. 

CrewLounge

Yea, I misspoke. The pressure is 45 psi, compression checks normal, new correct plugs, good vacuum, new ignition pick up and coil, etc.  They run like a champ. Good power and such.  Just started making oil and starting hard hot all of a sudden. 

212rowboat

making oil?  yeah... you've blown your intake gaskets and have a water passage leaking... or blown head gaskets... but you say it runs strong otherwise? sounds like intake to head water passage. 

CrewLounge

No, not any water in the oil. It's running so rich that not all of the fuel is burning

CrewLounge

And, engines run at 160 all day long

CrewLounge

Thanks Al.  I'll advise

MarkB

I don't think 160 is a problem. It's still in the norm. My engines run about there. I don't "make oil."  So is your oil thinning out? What are you doing to address that? Fuel in oil is obviously not good.

CrewLounge

Al,
they did. Said they had 45 on the front end and 23 on the back end. They pulled the heads and found both cracked around the intake valve stem jurnals leading.  They suspect it got hot sometime. May have been previous owner. I've had hard start issues since I've owned it. Thanks for you help

Michael T

I am very sorry to hear that. Did you purchase it from a dealer or Individual?  Maybe you have some form of financial recourse? Would it be worth the expense to turn your 377 into a 383 and at least get some fun for your grief? I hope this does not cause you too much upset,  at least the resolution should be auch better running engine.  All that hard starting had to be a PITA. Best of luck. Please let us know how things work out for You! 

CrewLounge

No need for strokers. The 342 is fun enough with the 6.2s. It only money. Isn't that what boat stands for??!!

Michael T

Actually you already have a stroker because  in reality a 377 is a stroked 350. If I had cooked heads I'd be looking at building a 383......it is only money and IMO a 342 with a set of 383s would be an awesome ride! 

Handymans342

Everything is better with diesels

raybo3

No way Handy......... No way...

Michael T

Steve,  just ask, VW if very thing is better with diesels. LOL

BellevilleMXZ

Alswagg said:

  With 1.6 ratio rockers these really come to life. 

I thought about a set of these for my 5.7 Gi......I know the GXi comes with them. An ECM flash needed with that swap?

Michael T

I normally agree with you Al and yes you would be boring out a 377a bit to create a 383 and yes you could go the rocker route (with some additional changes) but I disagree completely that doing so is in any way detrimental to the 350 block. My friends and I have had a number of 383s. Properly done a set of 383s in a 342 will  make a significant difference over 377s particularly in torque response. The first 350 I had stroked was set on the dyno at about, 380HP. We could have gotten more but at the expense of manageability and maybe longevity,  so we dialed it in at about 380. That was 15 years ago and it's still going strong. It's tongue is another story altogether as it ran a straight and awesome tongue curve all the way to 5200 RPM which no 377  could come close to in it's wildest dreams. 377, a nice engine,  388 another beast altogether. 

Michael T

No argument about that as you are correct (as usual),  just saying having owned a 383 and knowing their capabilities I'd be tempted to put a pair in a 342 and go embarrass some sea rays.  I think Mercury offers remanufactured 383s with a nice warranty but again that's $$$$$. But it is boating and it costs to have fun? 

Handymans342

Emissions  geeeeezzzzzz!

212rowboat

any fuel trim issues on a 383 can be addressed 'going with what you know', and is done on land all the time... given that on land most engines sniff o2 and have ability to adjust accordingly, but point is it's within the hardware's capacity to do so. 

you know the pressure at the rail... you know the delivery rate of the injectors... so, you choose an injector that passes more fuel without changing the spray characteristics of the injector.  We're not talking a huge range- we're talking likely 20cc's difference in delivery at an hourly rate.  If you're running 25# injectors which are delivering somewhere in the neighborhood of 265cc/hr, a #26 will spray somewhere in the neighborhood of 280cc... 

i'd wager that the difference in lift/duration by installing 1.6:1 rockers on a 377 is similar to running 1.5:1 rockers on a 383.  

give Bruce at FiveOMotorsports a call, and he'll set you on track... or, if you're feeling industrious:  here...