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After Engine Rebuild - Lack of power/Acceleration through entire range

Rick I'm assuming it has to do with gearing in transom
Not sure maybe changing prop pitch will change gearing that has been suggested by other shops and prop vendors as well as rebuild manufacturers
And Chris what is the answer then I for one really want to know because engine seems fine
 
MandMcustomperformance said:
Rick I'm assuming it has to do with gearing in transom.
Has someone changed the gearing while the old engine was being removed and while the replacement engine was being installed?


Not sure maybe changing prop pitch will change gearing
Absolutely NOT!

that has been suggested by other shops and prop vendors as well as rebuild manufacturers
They know not which they speak!

And Chris what is the answer then I for one really want to know because engine seems fine
Click to expand...

Once again....... the old engine was removed due to a catastrophic failure...... correct?
A like engine with MORE Horse Power and torque was installed........ correct?

If that is correct, why on earth would an engine with MORE horse power and torque require propping down?
 
MandMcustomperformance said:
Rick I'm assuming it has to do with gearing in transom
Not sure maybe changing prop pitch will change gearing that has been suggested by other shops and prop vendors as well as rebuild manufacturers
And Chris what is the answer then I for one really want to know because engine seems fine
Click to expand...

If it ran WOT before the build and now will not do it after.......there is something wrong in the build..... The Cam is what I am thinking. I know it pulled WOT on the dyno.......
The one thing that will limit RPM on a good engine is bad engine alignment......
 
Kind of reaching, but, what kind of boat is this ? Could it have become water logded while engine was out, or something happen to the drive or? or ?
 
Chris it does go wot the throttle lever hits the stop engine screaming like running at 6000+rpm
But tach reading 4000
And as I stated earlier same exact build was used on 3 other boats no issues
 
Docksidemarineservices said:
If it ran WOT before the build and now will not do it after.......there is something wrong in the build..... The Cam is what I am thinking. I know it pulled WOT on the dyno.......

The one thing that will limit RPM on a good engine is bad engine alignment......
Click to expand...

Outdrive is DPS-A 195, of which is a gimbal system drive and does require engine coupler alignment.


If I understood him correctly, he was and is running F5 props.

The previous engine was a 320HP 5.7GXIC-P engine.
The newly re-manufactured engine making 343HP at 5,000 RPM with 362 Ft/Lbs torque per dyno.

No one yet has mentioned how the hydraulic cam followers were adjusted.
 
What color are the spark plugs after a hard run on the water in forward gear? What is the fuel pressure? Revving the engine up without a load tells us absolutely nothing. Are the plugs burning a nice toasty brown?
 
MandMcustomperformance said:
Can't be alignment mounts are pre located and engine sits level
Click to expand...

Rent or borrow an alignment tool, and then look up the OEM engine drive coupler alignment procedure!

While I do not think that this is the performance issue, you certainly DO NOT want to be pulling this engine out for a drive coupler replacement in the near future!


Next questions:

1.... how were the hydraulic cam followers adjusted? I.E., what procedure was used.... static 2 or 3 stop, or the more accurate 8 stop?

2..... where is the spark lead at 3,500 RPM? I.E., how much ignition advance is each cylinder seeing at 3,500 RPM?

3..... would you consider using a crankshaft mounted degree wheel (along with the camshaft specs) and verifying the phasing up the camshaft?





.
 
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Rick I've done this enough times to know not to use bolts to seat transom

Kim after 10 hour break-in plugs were clean after dyno plugs were clean

Rick the boat is not here and can't give you advance on each Cylendar

Curious why we keep going back to the build
I pushed it hard for 10 hours straight if there was any failure it would have been noticed cam is ever so slightly over stock
I've been building engines for at least 10+years industrial, automotive, marine, agricultural
Some are over 1000hp I have had failures but few and far between but I can recognize when there is an issue in my engines.
 
Well... HP = torque x rpms /5250 ... (for ft-lbs and RPM)... If increased HP is achieved by increasing RPM, and a boat needs more and more torque to spin a prop as RPMs increase, you could have a situation where the dyno HP increases, but there is not enough torque @ WOT to spin a given prop. Additionally, gas engines have a torque peak RPM and output torque actually decreases as you rev above that speed, i.e. @ WOT... As stated above, the prop needs (eats!) TORQUE. Which leads me to... Chris's and Richardo's previous posts about the cam.

Also... re: "throttle lever hits the stop engine screaming like running at 6000+rpm. But tach reading 4000"

Anyone check the tach on the boat????
 
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Look, I'm on your side. I want to help the OP here as much as you do.

MandMcustomperformance said:
Rick I've done this enough times to know not to use bolts to seat transom
I have no idea as to what you mean "seat transom"!
The "transom" is a structural component of the boat's stern section.
The housing that connects to the transom is a Transom Shield.
The Volvo Penta stern drive connects to the Transom Shield via a gimbal bell.

Rick the boat is not here and can't give you advance on each Cylendar
Even while the ignition system is EST, and most mechanics will set BASE only....... I would still want to see what it is doing throughout the RPM range...... or what we refer to as the "Progressive" advance up to the "Full-In" RPM.

Curious why we keep going back to the build
Then let's put that to bed by answering my questions:

1.... how were the hydraulic cam followers adjusted?
I.E., what procedure was used.... static 2 or 3 stop, or the more accurate 8 stop?

2..... where is the spark lead at 3,500 RPM and/or above?
I.E., how much ignition advance is each cylinder seeing at 3,500 RPM up to the Full-In?

3..... would you consider using a crankshaft mounted degree wheel (along with the camshaft specs) and verifying the phasing up the camshaft?
I.E., verify that the #1 intake valve cam follower begins to lift at XXX* crankshaft angle...... and that it closes at XXX* crankshaft angle as intended by the camshaft manufacture.

Also..... which piston profile was used? Was a Quench Effect built into the combustion chamber? If so, what is the quench dimension?


I pushed it hard for 10 hours straight if there was any failure it would have been noticed cam is ever so slightly over stock
Please post the camshaft specs, and include the degree specs per crankshaft angle!

I've been building engines for at least 10+years industrial, automotive, marine, agricultural
I've been involved with the SBC since the mid 60's..... both in HP Auto and later in the Marine versions.
I am no stranger to this engine.

And by the way, I have NEVER built a SBC using that stupid silly GM Full Dished piston. It is totally incorrect for Marine use!

The SBC cylinder head incorporates a wedge style combustion chamber.
This SBC cylinder head has a rather substantial quench surface above the main chamber.
The Marine version SBC needs a quench style combustion chamber in order to eliminate the Detonation potential.
This cannot be achieved with the GM F/D piston! :mad:

Sadly, GM has continued to use their Full Dished piston in the 5.7s, the 6.2s and in the 6.3s. (5.7 = 350 cu in, 6.2 = 377 cu in and 6.3 = 383 cu in)
Click to expand...

My unsolicited advise:
Everyone involved with “hands-on“ needs to get on board with the P of E (process of elimination) procedure!
This involves checking/testing/verifying one item and one item ONLY at a time.
Move on to the next suspect item ONLY when the previous item has been found to be OK, or has been found to be faulty and has been corrected.
This is the only way that you guys are going to solve or rectify the issue!
Anything else will be nothing more than guess work and will be very time consuming!

Roll up your sleeves and get dirty!


And again..... I'm on your side. I want to help the OP here as much as you do.


.

 
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Dang..... I am not able to edit my last post.

OK..... a few more questions:

1... has anything to the stern drive been changed or altered while the engine was being replaced? Any chance that a different drive ratio was accidentally installed?

2... are these the exact same duo props that were used with the previous engine? Were they sent out for tuning, etc?

3... has the hull been sitting in the water during the engine R&R? Any chance of excessive marine growth on the hull? (this can make a huge difference)

4... any chance that the rubber hubbed drive coupler has become damaged?



I believe that the guys here, including myself, all want to help where we can.
However, we need as much good, solid and accurate information as we can get from you.

I know for a fact that we can be of more help if our questions are answered accurately and fully. Until then, our hands are somewhat tied behind our backs.


.
 
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.................
MandMcustomperformance said:
No it was on trailer
OK, then that will eliminate the concern for any marine growth!

Transom was removed and stored in dry building
OK, since we are discussing a Marine engine on a Marine forum, I need to call you to task.
A "Transom" is a structural component of the boat's hull.
A "Transom Shield" is the Volvo Penta unit that is bolted to the structural transom.
The stern drive attaches to the transom shield.
The transom shield itself does NOT need to be removed for engine R&R.
However, the stern drive DOES need to be removed for engine R&R due to the propeller shaft's penetration and engagement into the rubber hubbed drive coupler.
(many know this by the term "input shaft".... technically this is a propeller shaft)

No gears were not touched
OK

No checked all rubbers
Including the coupler?

Yes same props were only wiped down and polished by hand
OK
Click to expand...

Now on to the questions that have not been addressed:

1.... how were the hydraulic cam followers adjusted?
I.E., what procedure was used.... static 2 or 3 stop, or the more accurate 8 stop?

2..... where is the spark lead at 3,500 RPM and/or above?
I.E., how much ignition advance is each cylinder seeing at 3,500 RPM up to the Full-In?

3..... would you consider using a crankshaft mounted degree wheel (along with the camshaft specs) and verifying the phasing up the camshaft?
I.E., verify that the #1 intake valve cam follower begins to lift at XXX* crankshaft angle...... and that it closes at XXX* crankshaft angle as intended by the camshaft manufacture.

Also..... which piston profile was used?
Was a Quench Effect built into the combustion chamber?
If so, what is the quench dimension?



I'm trying my best to help here...... but this has been similar to pulling teeth without Novocain. :)

 

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MandMcustomperformance said:
Even if bad why would it effect the wot hole shot?
Boat stands up but no forward launch
Click to expand...

Did I miss this earlier? Lets start over.
You put the throttle down and the boat stands up on the transom? How long before the bow comes down and you are on plane? Is the drive able to tuck all the way in? Maybe you should take a picture.


The reason I go back to the build is.....
When you change the air flow through the engine with a non-stock rebuild on a MPI comp controlled system, it changes the VE. Being an MPI engine the cam profile and compression ratio are critical to performance. If these are changed the Ecm has to be remapped.

With your dyno pulls and the hours already put on the engine, there is nothing wrong with your assembly, including the rocker arm adjustments.
 
Ecm re-mapping was not done
This could very well be issue
I would take pics but boat not on my property anymore
Jay is in possession of the boat
I am guessing here but I would say it takes roughly 10-15 seconds to get on plane once trimming has started
 
Are the plugs toasty brown? Did you increase displacement? If the plugs are a powdery white it is running too lean and it will cook the valves in short order. Can you flash the ecm and increase the injector pulse width (chip) or put in larger injectors? Just throwing stuff out there the plugs will tell you if it is running too lean.
 
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