Performance of my 383 stroker!

[joewithaboat]

Re: Performance of my 383 stroker!

Unless the c/r, heads, intake, cam, injector size, fuel pump etc... are all the same as the Mercruiser 383 that tune is not optimal and is probably why it is not performing well.

If both engines, your old 350 & new 383, were exactly the same except for the stroke. The 383 would need a little less timing, a little more fuel, have quite a bit more average torque (because it would come on sooner), make a little more hp.

You need to be able to compare exact specs of the merc 383 and your new 383. You will probably need a custom tune.

 

[QC]

Re: Performance of my 383 stroker!

Ayuh,... I wish I could help ya, But there's 'bout 1 Million ways to build, prep, 'n tune a Chevy stroker motor.....

Especially, when yer talkin' 'bout a reflashed 'puter....

The more I think about this, the more I believe this is the only answer. Stinks that it is not a very good one, but there you go. Speed is all about Horsepower. Horsepower is all about fuel. Fuel is all about air. When you built the new engine, the way they built it to get more power changed how much air and when. There is not a flash file matched to that. There used to be a 377 Scorpion. And it was rated at 377 bhp at the prop. Your 410 if it is a true 410 at the crankshaft would be rated at around 380 at the prop by Merc. Maybe that flash file would match "better". But it may not be an exact match. And what I don't know is if you take any of these flash files, what happens if there is more air available? What if you put a 260 (prop) 5.0 MPI file on a 502? Flip, I don’t know. You need to find someone who actually knows, and it can’t be someone who just thinks he knows, and therein lies the problem. The only guy that knows is a guy who has tested a bunch of combinations: different iron, with different electronic fuel and air maps. I don’t think that guy exists here. Maybe he does at Merc, and maybe some garage guy does too, but anybody else is speculating.

Edit: Joe was making the same point with fewer words

 

[FReade]

Re: Performance of my 383 stroker!

I just took it out with a 21pitch prop I borrowed on it place of the 19. The rpm was still at 5000 and speed about 51. I'm looking for a 23 pitch now.
It has to be the computer! Waiting for a reply from Simon Motorsports that OBD told me about. I'm thinking it may be best to buy the software (if its not to high) and find someone local that knows how to tune.
Or should I just take it out and send it off (with the specs)?

 

[rschap1]

Re: Performance of my 383 stroker!

Still an awful lot of variables here.
Yep, for sure the computer needs to be mapped to match the motor you got in there.
BUT, even with a perfect tune, you may not be able to realize everything you could or should.
CAM is a biggie. If it's power range doesn't match the rest of your motor and everything isn't suited for a marine application, you could be wasting your time and money trying to tune for the cam, heads, intake, and exhaust you are running. Stock cast iron exhaust manifolds and risers? That 410 hp rating may not have been reached with MErc manifolds and risers...I am guessing that best method would actually be installing an air/fuel ratio monitor and having a "tuner" ride along and create the maps needed if the other parts are correct and work well together as a combo.
Good luck!

 

[FReade]

Re: Performance of my 383 stroker!

http://www.usengine.us/marine.html

383 Stroker 410 h.p 1996 - 2011 8 or 12 Bolt Intake Manifold

$3,295



383 stroker is made from two engines, the Chevy 350 and Chevy 400 engine. From the 400 Chevy we use the crankshaft however our 400 crankshafts are new. The 400 crankshaft is fitted into the Chevy 350 making a longer stroke



350 rods are used with special designed pistons. The cylinder heads, camshafts, timing gears and valves are all from the Chevy 350 engine. The Chevy 383 stroker makes more horse power but what most do not know the 383 stroker has much more torque.

Torque is what you need to move heavy loads like boats. Think of torque and horsepower this way. Big diesel trucks have 300 to 400 horsepower, but what moves them down the highway is their torgue 1,200 or more.

We have installed Chevy 383 strokers in customers boats and gained 15 miles per hour however you must change your prop to gain 15 MPH or you can have massive torque power up to 5,200 RPMS. Not changing your prop makes your boat great for pulling skiers and tubers. If you have 383 stroker marine questions just call we will be pleased to help
350 boat engine

__________________________________________________________________________________________________________________

Yes you need a tune that is not a merc engine and if you go there you will need to get the cam card actually all of the major details... so obd can tune the engine..They cannot guess

Id bet your in a pickle here... that is no one to custom tune a merc 555 system. You can still do this though... replace the 555 with a mefi 4b harness and ecm about 700.> your mech owes you one for having a new block flashed for a merc engine they are not even close. Opps and obd can tune that 383 with a mefi ecm

US Engine won't give me any response! I gave them the date they charged me the $4661.78 on my credit card (not $3295) and they can't find the info on it. The service person said they needed the engine #, and I've been trying to get it but havn't heard anything! When I first took the motor to the installer, he called me and wanted me to return it because it wouldn't turn turn over (still on the pallet) a bolt was hitting the camshaft lobe or something. US Engine's response was have them grind it down. They did but I was expecting a quality marine engine that had at least been checked since I was told it was balanced and blueprinted!! I bought from them because they stated a 7 year warrenty. Then that happened before even installing. They originally told me they would have it picked up but then later I recieved an email from a Mr. Silvers stating he was the boss and they would not be picking it up! Thats why I'd rather find someone else help me.

 

[rschap1]

Re: Performance of my 383 stroker!

Sounds like you are getting screwed a bunch of ways.
Why would you allow an extra $1800 on your cc??
The bolt hitting a cam lobe....???
LOTS of strange stuff here.

 

[joewithaboat]

Re: Performance of my 383 stroker!

Call your credit card company! They will give you all kinds of attention then, because they will get a charge back.....

 

[QC]

Re: Performance of my 383 stroker!

I don't think the OP is saying he was overcharged. Reread everything. He did not get that deal. Maybe he ordered some options? Manifolds? Etc.

 

[FReade]

Re: Performance of my 383 stroker!

I don't think the OP is saying he was overcharged. Reread everything. He did not get that deal. Maybe he ordered some options? Manifolds? Etc.

No options but balance (if they charged extra for that) I paid the mechanic for the manifolds!

 

[joewithaboat]

Re: Performance of my 383 stroker!

No options but balance (if they charged extra for that) I paid the mechanic for the manifolds!

Balancing, depending on application, could range from about 100.00 to 400.00 tops... Unless heavy metal is needed (not likely). It can get crazy from there depending on how much heavy metal you need.
Any shop that doesn't encourage balancing as SOP should be avoided, IMHO.
I used to do this...