383 stroker problems

[MFZ1969]

anyone out there re-powered with merc 383? Ive had nothing but problems, 1st engine leaned out #8 cylinder within 12 hrs, warranty replaced the longblock, 2nd engine did the same at about 60 hrs, what is going on? proped correctly, not abused, put in a 98 fourwinns 225, with a new sx cobra outdrive 1.5..... anyone else having trouble with this motor?

 

[JustJason]

Re: 383 stroker problems

1st engine leaned out #8 cylinder within 12 hrs, warranty replaced the longblock, 2nd engine did the same at about 60 hrs,

with a new sx cobra outdrive 1.5.....

So you have a Merc engine and a Volvo drive????

Either way... you answered your own question... If it leaned out, I'm assuming you melted a piston. Leaning out has nothing to do with the mechanicals of the engine, and i'm surprised it was warranteed for you. You need to go through your engine fuel system. Making sure the boat side fuel supply is good, fuel pump output is good, and the carb your using is good enough for a 383 and properly jetted for one. You also need to make sure you have no air leaks on the intake manifold or carb base. If you just took a carb of a 350 and stuck it on a 383 (more displacement means more fuel needed) without re-jetting it, i'm not surprised your having problems.

Funny thing about running engines lean... They run pissa right up till when they blow themselves up.

 

[z284u2try]

Re: 383 stroker problems

fuel injected or carbed?
What plugs are you running?
Do you look at the plugs after running it?
# 8 cyl. Is very famouse for killing itself on many different size engine but I mostly see it in high compression n/a engines or forced induction/n20 applications.

 

[dr_bowtie]

Re: 383 stroker problems

as stated you have a fuel issue not an engine issue...

the rear of the block runs hotter than the front and thats why you see rear cylinders going away first...

after it was initially run the plugs should have been checked and looked at...

proof would be 2 engines died of the same cause...not likely to happen if the fuel was right...

 

[John_S]

Re: 383 stroker problems

Didn't these all come as MPI's and as complete packages? I know the 377 only came in MPI, but not 100% sure about the Merc 383 engine replacements.

 

[TilliamWe]

Re: 383 stroker problems

Didn't these all come as MPI's and as complete packages? I know the 377 only came in MPI, but not 100% sure about the Merc 383 engine replacements.

The only one from mercruiser is called 383MAG MPI.

 

[z284u2try]

Re: 383 stroker problems

Well if its mpi I would check that injector. Could be clogged or not spraying enough fuel. Injector harness wire problems. I would flow test all 8 injectors and the highest flow rated one would now reside over #8. Sounds like a fuel delivery problem.

The plugs you are running could be too hot of a heat range not helping the problem.
I would read the plugs on your next build with partial throttle and wide open throttle readings.

 

[Fun Times]

Re: 383 stroker problems

anyone out there re-powered with merc 383? Ive had nothing but problems, 1st engine leaned out #8 cylinder within 12 hrs, warranty replaced the longblock, 2nd engine did the same at about 60 hrs, what is going on? proped correctly, not abused, put in a 98 fourwinns 225, with a new sx cobra outdrive 1.5..... anyone else having trouble with this motor?

Did a new intake manifold come with the new long block? Could have a problem some place with it as well if it is the same one from new.http://www.mercruiserparts.com/Show...0&bnbr=90&bdesc=Intake+Manifold+and+Fuel+Rail.
But start with the fuel system & spark plugs first, Ect, Like every one eles was talking about above. I wish you good luck with it.

 

[Apollo75]

Re: 383 stroker problems

anyone out there re-powered with merc 383? Ive had nothing but problems, 1st engine leaned out #8 cylinder within 12 hrs, warranty replaced the longblock, 2nd engine did the same at about 60 hrs, what is going on? proped correctly, not abused, put in a 98 fourwinns 225, with a new sx cobra outdrive 1.5..... anyone else having trouble with this motor?

I agree with the previous posts ---- sounds lean --- need to check your rail pressure first.

To make the most torque with an engine under load --- air fuel ratio needs to be around 12.5 to 13.5 to 1. I cannot say what the stock AFR is ---- this has to be measured on each cylinder and on a dyno of some sort. I would assume mercruiser has checked this and if it is a 383-setup with the correct pound injectors then it should not be running lean.

Here is a link ---- dated but it makes no difference carburetted or fuel injected.

http://www.the-crankshaft.info/2009/09/air-fuel-requirement-in-si-engines.html


Best of luck

OFM

 

[bruceb58]

Re: 383 stroker problems

There are a few things here that do not make any sense so we need to wait for the OP to get back. Last OMC Cobra was in 1996 so not sure how thiis ended up in a 98 boat. We also have no idea what fuel system he has.

 

[Apollo75]

Re: 383 stroker problems

There are a few things here that do not make any sense so we need to wait for the OP to get back. Last OMC Cobra was in 1996 so not sure how thiis ended up in a 98 boat. We also have no idea what fuel system he has.

Excellent point

Aye aye Admiral

OFM

 

[Richie086]

Re: 383 stroker problems

I'm watching this thread carefully.

My 1992 Doral 255 MC is being repowered with a factory fresh Mercruiser 383 bravo stroker MPI 350 hp engine as we speak. It's supposed to be an excellent replacement engine for my carbureted Mercruiser 7.4L 300 hp.

 

[bruceb58]

Re: 383 stroker problems

Since the OP posted on October 1st with his 1st and only post, you are going to be waiting awhile.

 

[Liberator86]

I’m having a problem with a383 stroker just rebuilt. Won’t go above 3800rpm

 

[jbcurt00]

I’m having a problem with a383 stroker just rebuilt. Won’t go above 3800rpm

Start a topic about your 383 and ask about your motor there

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