Needing a little help here......

[Bigdave196]

Ok, Im a NEWB here and I am calling out for some help before I have to shell out more greenbacks to get this minor problem fixed.
I have a 1995 Bluewater Open bow ski boat with a 5.7 going to an Alpha1 outdrive with a Steel Quicksilver 19-pitch 3 blade prop. Last year we had the brilliant idea to run out 2 year old gas instead of pumping it out and leaned out the #4 cyl. Well $2000 later we had the motor rebuild by a very reputible shop and bumped it from 220hp to 300hp. I am running a factory distributer with Accell 8mm wires and a MSD Blaster coil for 50K volts of spark to AC Delco Iriduim plugs. Factory Elelbroc Carb (4bbl) unknown size for CFM. With the last motor I could easily turn 4900-5500 RPMS and get around 60MPH with this setup. Timing was factory.
New motor now has almost 80HP increase, and Timing is at 15 degrees BTC. I have awesome hole power now (compared to when the #4 Cyl was shot) and the engine runs so smooth, but now it wont pull over 4000rpm. I am maybe getting 35MPH out of the boat so far. I have played with the air/fuel screws to get it to this RPM, but I cant get any further. I do not want to lean it out again and I am at a loss for what to do. The builder of the motor said that to hear this boat "sing" I need a Demon 800 Marine carb. Thats $800 that I really dont want to spend unless I have to. So my questions are,
1. Do I have a CFM issue with the old Carb because I went up 80 HP?
2. Do I just need to re-jet my carb?
3. Is my Edelbroc carb just insufficient to handle 300HP?

Any other ideas on where to look or what to look for??

This boat has given us almost 1000 hours of enjoyment and we keep in in really good shape, and now I am frusterated.
Thank You in advance.
Dave

 

[Bondo]

Re: Needing a little help here......

Ayuh,...

#1,.. Nope,... Shouldn't be...
#2,.. Possibly...
#3,.. Again, Nope, it should run just Fine, even at 300hp....

Go to Edlebrocks website,+ search for their Tech Manuals....
Somewhere there, they have an Awsome Manual for the performer carbs...

 

[Maclin]

Re: Needing a little help here......

My personal opinion is that any late model Marine Edelbrock 4bbl should be able to hang with those mods and not limit an engine like that, meaning an arbitrary rpm. This is of course barring any fuel delivery issues.

My second thought is that the valve lash is not quite right and as the lifters pump up the valves can't close all the way against the compression above a certain rpm.

Fuel delivery issues usually manifest themselves in other ways like surging, backfiring, etc.

I would want to put double checking the valve lash as the first thing to look into.

The a/f screws should only affect the idle and "transition" to the mains as rpm's climb above 1500. The jet and metering rod "mains" combo is what determines the a/f ratio with the throttle open.

You should be checking the spark plugs to make sure they are the dark tan and have no deposits. Checking them is the simplest way to check for a lean detonating condition.

 

[Bigdave196]

Re: Needing a little help here......

Also, this was brought to my attention. Could my Secondaries on the carb not be opening, or opening all the way???

 

[Maclin]

Re: Needing a little help here......

The Edelbrocks use a weighted air door on top and manually opened butterfly plates so unless the linkage is messed up the top air door almost has to fall open if the engine needs it and the throttle is far enough open

You can see what I mean by manually tapping the secondary air door, looks like a choke plate except it is on the secondaries. The air door can be pushed open easily. Hold that foor open, then push the throttle open, the secondary butterfly plates will start to open part way thru the throttle travel and will be fully open at WOT, that's all there is to it. In operation as the secondary butterfly plates open and the engine can draw more fuel mix then the air door will be drawn open by the flow and Voila, more cfm.

If you have an automotive carb, some of those had a choke lockout, so while the choke is closed the secondary linkage is locked out. That would be rare but I had to mention it because I cannot look your carb over in person. QJ's and TQ's and some Carter AFB's had that. Not sure about Eddies but they are rebadged AFB's so I had to bring it up.

 

[Maclin]

Re: Needing a little help here......

Sorry meant to mention that YES check your throttle travel , make sure the carb is at WOT when the helm throttle lever is at WOT.

 

[Bigdave196]

Re: Needing a little help here......

Thank you all for the replies so far. I also spent 20 min with the Edelbroc tech and he said that it may also be a fuel delivery issue (PSI). Because I did change cams and such, the mechanical fuel pump might not be getting used to its full potential. Is this possible? That in RPM's the mechanical pump can sustain enough fuel pressure but that the fuel pump isn't moving enough fuel to run the motor at 4000+ rpm? Could a change in cam hinder the pump performance?

 

[Maclin]

Re: Needing a little help here......

I suppose the wrong eccentric on the cam could make a difference but the engine builder should have had that under control. The eccentric is either there or it isn't, later model EFI's did not need the pump eccentric.

Does it surge at WOT? Or just act like it is out of breath? If the pump cannot keep up then it usually starts to die as the RPM's drop when the bowl is empty then surges again when more fuel hits the bowl. This action may or may not be pronounced but you should be able to feel and hear it in my opinion.

Throttle travel.
Valve lash.
Hut Hut ...... (get busy!)

 

[mylesm260]

Re: Needing a little help here......

Carbs have a reserve built into them, the float bowl.

If your pump was unable to keep up, I would wager your scenario would be more like this:

20% throttle engine runs fine
50% throttle engine runs fine
80-100% throttle, engine runs great, pulls hard for a few seconds, then starts backfiring through the intake (popping)

As someone else suggested.... go out on the water with a spark plug wrench, run the motor where you're experiencing the problem, then quickly shut it down, and pull the plugs and read them. Plugs will tell you your A/F situation (rich or lean).

The back page of any automotive haynes manual will tell you how to read them.

If they read normal (light tan, I believe) than you know your a/f ratio is good. Then I would look into spark curve and carb linkage.

The fact that you've got lots of bottom end does lean towards the spark advance or carb secondaries failing to open theory.


When you check the timing, are you following the proper procedure? (disconnect vacuum line, or if electronic, crossing a connector perhaps)

Do you understand how your advance system works on your boat (centrifugal, vacuum, or electronic?)

 

[Bigdave196]

Re: Needing a little help here......

Motor pulls like a "Bat out of Hell" from an idle in gear to 3800 or so RPM. Major hole power increase from the previous motor of 220HP. Then about the 3500 to 3800 or so it just peaks the same way it would when your just out of throttle. Responds almost the same as it used to at around 5500rpm. No hesitation, surges, sputtering, or anything.

 

[mylesm260]

Re: Needing a little help here......

check your throttle and carb linkage, make sure your secondaries are setup properly.

Check your timing properly, and verify that your timing does change with load/rpms as intended.

I can say with 95% confidence it is NOT A fuel delivery problem. There's another post a couple down from yours right now with someone experiencing fuel shortage on a 3.0L. That's what fuel starvation is like.

 

[Bigdave196]

Re: Needing a little help here......

The fact that you've got lots of bottom end does lean towards the spark advance or carb secondaries failing to open theory.


When you check the timing, are you following the proper procedure? (disconnect vacuum line, or if electronic, crossing a connector perhaps)

Do you understand how your advance system works on your boat (centrifugal, vacuum, or electronic?)[/QUOTE]

With everything in place ( and no i didnt know to pull a vaccume line) at idle the timing is at 15 degrees and when the motor is reved in netural it goes strait to the 12'o-clock position with the timing light. Didnt know there was a proper procedure to check timing. But I did set the timing while on the water while my wife ran the throttle and I was in the engine compartment.

 

[mylesm260]

Re: Needing a little help here......

That might be the right way to set the timing, and it might not. You need a manual that corresponds to your ignition system. Figure out what year and model of engine your current distributor is from, and use the manual for that engine.

I have very very little experience with older marine setups, so I honestly don't know for sure. I would wager there's something you have to do to set the timing.

The fact that your timing changes with throttle is good. It means your advance system is likely working properly.

I just did some quick google research.
(keep in mind this is likely not your exact model, but just an example)

http://www.perfprotech.com/store/articles/mercruiser-engine-timing.aspx

V6 and V8 Carbureted Models (Thunderbolt V Ignition)

1. Connect timing light (91-99379 or similar) to No. 1 spark plug wire. Connect power supply leads, if applicable, on light to 12 volt battery. Refer to Specifications ? ?Engine Rotation and Firing Order? for cylinder numbering and location.
2. Connect a shop tachometer to engine.
3. Using a jumper wire, connect the ignition system timing lead (PUR/WHT wire) to a good engine ground (-). This locks the ignition module into the ?Base Timing Mode?.

NOTE: Before starting engine make sure the timing tab and marks on damper are clean. Chalk or white paint on timing marks may help visibility.

4. Start engine and run at normal idle speed. Allow engine to reach normal operating temperature.
5. Aim timing light at timing tab, located on the timing gear cover and crankshaft torsional damper.
6. If adjustment is required, adjust timing by loosening distributor clamp and rotating distributor body as required until timing mark on damper or pulley lines up with the mark on tab specified in ?Specifications?. Tighten clamp and recheck location of timing mark.
7. Make sure that the distributor has been tightened. Remove the jumper wire from the timing terminal.
8. Remove jumper wire between the timing lead (PUR/WHT wire) and ground (-).

IMPORTANT: Be sure to disconnect the jumper wire from between the ignition system timing lead and ground (-) before attempting to resume normal operations. If the jumper wire is left in place, the ignition module will operate in the ?Base Timing Mode?. This means that the additional timing advance features would not function.

9. Stop engine and remove timing light.

 

[Maclin]

Re: Needing a little help here......

I am not sure what the "factory distributor" in your description means there Big D. If it is a "factory mercrusier" then it is part of a larger system and there is a definite way to set the timing. Because of how you described the initial timing setting it sounds like it is not a Merc T-bolt or other from-Merc setup.

But I would want to know the total advance as well, that is best done with a dial-back timing light. If it is not a Merc setup then I would want to see the dwell also just to make sure something inside is not out of phase or set incorrectly. I have seen improper dwell in an electronic ignition deliver killer bottom end then flatten out dramatically.

If there is 22 degress or more advance built into the distributor then at 15 degrees initial you have 37 degrees total and that is close to the top of what it may be able to take. Hotrod engines are usually at 38-40 and that is with good fuel, lower gears, etc.

 

[mylesm260]

Re: Needing a little help here......

Yes, that's also a very very good point.

You mentioned an aftermarket coil (MSD blaster)

for argument's sake, have you tried going back to the stock coil to test the problem?

Often times, when your running a bigger coil, your current and dwell settings go all to hell. For example, OEM's often put dropping resisters in series with their coils to lower RF interference. If you put a bigger coil in place with a lower impedance, then the balance between this resistor and the coil can be way off, and your left with less spark than when you started.

But be careful, removing this resistor may overheat your driver (ignition module).

If this was an automotive application, I would suggest removing your resistor, and using a good aftermarket GM style 4 pin HEI module on a great big heat sink. My experience is they work very very well with larger aftermarket coils. They take care of the current and dwell problems. Be warned though, they get very very hot with big coils, if you don't bolt them properly to a heat sink, they will fail.


Honestly, bigger aftermarket ignitions coils is more of an issue on forced induction motors. If you find going back to the stock coil solves your problem, you might be better off just to scrap the MSD idea all together.

 

[Bigdave196]

Re: Needing a little help here......

Ok, The MSD Coil is a "Blaster 2" and the wires were ACCELL 8mm wires that were "Cut to fit" for your application. These were installed 2 years ago and ran perfectly for the season. Then the boat was put into storage from '06 to Thanksgiving '08. Thats when we leaned out the #4Cyl. I wouldn't think that it would make a difference now, or would it? I was actually getting ready to replace the coil and wires really soon. I already did the plugs and cap&rotor with the rebuild. Would have done all of it, but they were out of stock.

 

[mylesm260]

Re: Needing a little help here......

Okay, we need more information.

What has been done to the boat since it was running good.

You mentioned engine work, what was reused and what is new?

Did your mechanic rebuild your long block, and you reinstalled your old carb, and ignition system, and now it's not running as well as before, even though your internals have been upgraded?

 

[Bigdave196]

Re: Needing a little help here......

Ok, All internals were brand new from the rebuild. New crank, cam, rods, pistons, bearings, timing chain is double roller, valves, and valve springs ect...ect...
I reused the same Edelbroc carb (600cfm) and Edelbroc assured me that since I am not breaking 6000rpm that the card is perfact for the application. We have resued the factory "Mercruiser" Distributer and replaced the Cap and Rotor. We reused the Accell 8mm wires and replaced all the Spark plugs with Iridium AC Delco's.

The motor was a 215 HP Mercruiser Chevy 5.7 and now its a 300 HP chevy 5.7 bored out .020".

The last thing we did to the boat before it leaned out the #4 Cyl was a tune up 2 years prior that involved the new plugs, wires and coil along with a new cap and rotor. The boat ran flawlessly all season then it went into storage for almost 2 years.

The engine builder installed the carb and intake manifold, and the distributer once he put the motor in TDC. Then using his winch to lower the motor into the boat.
I then went home, reinstalled the Powerstering pump and alternator to the motor, water pump, all 10 or so wires to the dist, temp sensors, and such, exaust manifolds and things of that nature. Everything went back into place like a glove since it was in that shape for 13 years. The wires literally laid down into place to within an inch or two of each connector. All guages work, and all sensors are reading properly. I bolted on the Throttle linkages that mount to the two back bolts of the carberator/intake bolts, and the transmission linkage to the exaust manifolds.
Last weekend (Easter Sunday) we took the boat out and Timed it to 15 degrees and its everything you would expect out of a 300 hp motor until you just run out of rpms at 3800 to 4000 ish.

Other than that what else would you like to know?

 

[krisnowicki]

Re: Needing a little help here......

15 btdc is a little far have to tried moving to 10 or so ....

 

[Maclin]

Re: Needing a little help here......

I am thinking like krisnowicki, I think you have too much initial advance and the TBolt control unit is adding advance way past what the engine can stand at the upper rpm's. That is why I was asking about what dizzy you had in there earlier.

Gotta get the TBolt into base mode first I think before setting the initial.

You could just try retarding the dizzy just a bit, although following proper TBolt timing procedure is best.