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Help, 5.7 woes

wildfrahm said:
BT, thanks for #'s everytime I order it's a pain. Chief my fuel pump went out and I put a auto unit on,I plunged off the vent on carb. Have another brand new carb. Am going to switch out also before I go outt.
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You need to remove the auto pump from your engine and install the marine pump or an electric pump with an oil pressure cut off switch.
You have made your boat dangerous to operate by installing an automotive pump!
If the pump Diaphragm goes bad it will fill your bilge with gasoline. The plastic hose to the carb was put there for a reason.
 
"Have to take break. to summerize, I took out today with portable tank, ran worse, took right out brought home checked timing was well above TDC, readjusted to 8BTDC as spec. checked oil was quart low, performed compression check,
1-130, 3-140, 5-135, 7-133, 2,4,6,8 were all 130. Manifold vacume at idle (900 in neutral in driveway on muffs) was rock steady at 18. checked plugs 1,7,2,8, were all tan, 3,5,2,6 were all black but not fouled. Have clear fuel filter but not changed element, could not tell if gas was in filter was so full of fuel. not sure how normal that is."

If you are losing a quart of oil, and plugs 3 and 5 are rich and 2 and 6 ( was hoping to see plug 4 rich) then I would think intake manifold leak. Plugs 3,5,4 and 6 are next to the heat crossover port. Loose intake bolts or blown gasket will cause this. Also its an internal vacuum leak causing the carb to run poorly. WHat happens is oil is sucked up into the leak between the intake and heads. Even tho you got 18 inches of vacuum, you might be surprised to get higher. Also running on muffs is no back pressure so vacuum is higher. WHen you rev motor to 1k rpms does the vacuum rise higher?

Timing also has impact on vacuum, low timing will have lower vacuum readings. Since you changed out dist for an electronic one, initial timing is no longer valid as the timing advance has change. Use a timing light and rev up to 2000 rpms note advance amount, easier with a dial back light. Or temporaily disable mechanical advance and set timing to 28degrees. See if runs better.

I have just been down this path, new (less then 15hrs) twin engines, starboard wouldn't run past 3k under load. Tried new dist units, swap carbs, checked cam timing, finally pulled intake and the gaskets were oily. reassemble got 3 inches more vacuum (was idling at 14inches) and was able to find the minor carb issue(got another 2 inches). Motor idles 800 rpms 20 inches vacuum, initial timing sitting at 12 degrees.
 
don't think I lost oil. just did oil change few weeks ago.probably dum dum. am planning on working timing and coil today. went to manufactures website and found they say don't use the coil I am using.
Am also going to change out carb. My fuel looks like iced tea only darker, full of debree floting around. have changed and cleaned water seperator and changed fuel filter. But current carb was on boat before all of this. I have not cleaned tank, I am running on 6gal. above deck tank.
And I ordered a stock fuel pump for my motor this week end.
Also want to add that I run two of the oil socks in my bilge. they are clean. I had a oil leak that I fixed. I then cleaned bilges. You can sit in good clothes and work on motor and not worry. I belive that is where the oil that I lost went.
 
OOp's was looking at earlier post and on my plug condition I listed #2 twice, Should have read,
1,7,2,8 were all tan,
3,5,4,6, were ball black,
Or to say the four corners were tan and the 4 center were black.
Can I have a vacume leak with steady vacume reading?
The reason I put a auto fuel pump is was not sure which I was using. Marine pumps rum 100.00 and auto 30.00.
 
Wow, I think I figured it out. And it goes against everything I believe and try to pratic, patience. When I first started with this motor I was suffering from impatience and installed carb. But did not adjust choke. On this carb there is a stop that prevents the secondaries from opening until the primary is all the way open. Which cannot happen with choke running so rich that the primary only opened half way! Also found right hand bowl empty. Was clogged from debris, so I switching carb. And adjusting choke.
 
I'm thinking you may not be firing on all 8 cyls. start by either doing a compression test cyl by cyl or by pulling one plug wire at a time, if you pull 1, 2 or more then don't seem to make any difference when she is running, you have head / cyl problems. I have the 5.7 and this is where I am at this time, pulling my cyl head now in fact. Raw water ingestion via exhaust system, seems to be a common problem on these 5.7 Mercruisers. I've read hundreds of post with same or similar conditions. I had less then 20 hours on a rebuild and I am not a happy boater at the moment. Wondering how Mercruiser has managed to get by with these issues with their engines for all these years? New, rebuilt and re manufactured engine failures, just doesn't sit well with me at all. Anyway, do the compression check before you spend another dollar or minute doing anything, also don't trust your dip stick to show if you have water in your engine, it will not always show water / white in oil from dip stick. You'll have to drop your oil to be sure, period there is no other way to know for sure other then seeing water on your plugs ( cyl ). Let us know what yo find. Good luck! I feel your pain!
 
I'm chiming in very late on this one, so forgive any redundancy.

Your first post suggests that you can't get above 2k rpm.
When all else has been eliminated..... good spark, good fuel delivery, correct prop pitch, clean hull, correct gear ratio, etc......, check the ignition advance... not BASE, but check the progressive advance that occurs in addition to BASE advance.
It's just too dang important to NOT check!
Without the correct progressive advance, our engines will not produce the power that we expect.
Normally, I do this in reverse order (making this first on my list), but many DYR's will leave ignition advance until last.
And many times will find this to be the culprit when older worn mechanical ignition advancing systems are used.


Regarding your Hall Effect conversion kit:
I'd ditch that Hall Effect triggering system, and install a good new electronic ignition system, such as Mallory's YLM series that uses VR triggering. Anything but a Hall Effect conversion kit!
The conversion kit does ZERO for an older distributor that may not be offering the correct Marine advance curve and limit.
As noted...... this is very important!


I understand what member Paw2000 is saying re; timing.
However, and very important here..... DO NOT allow too much advance at these lower RPM.
See your OEM specs and DO NOT deviate.
Set BASE, but realize that BASE is BASE, and that's all.
We fire on BASE, and we idle on BASE.... we don't run on BASE.
We operate on the correct progressive advance.

You should see your Full-In advance being spec'd at/around 3.2k rpm, and no lower.
You should also concern yourself with the correct advance "curve" as per OEM.

Full-In advance at anything near/at 2k rpm is a recipe for Detonation Damage :mad: :mad: :mad: .... 28* @ 2k rpm for example! :mad:
Again, see your OEM curve.

Also, and not very popular among the Digitally Advancing timing light owners, try to mark off your harmonic balancer up to 35*, and strobe this with a Std Timing light, and/or a digital timing light that is in Std Mode.
This allows us to view the advance in Real Time/Real Degrees.
One user error, or one mis-calibration and/or error in/of the equipment........, and you could be off by several degrees.
Not worth the risk, IMO.
If it wasn't so dang important, I'd be OK with the digitally advancing type lights for this!


Also, and not wanting to beat a dead horse here.... but know your engine build.
If the full dished pistons are used, we cannot throw as much TA (total advance) at this type engine build.
Conversely, if the Quench Effect style pistons are used, we can throw a tad bit more TA to this type build engine, offering us better performance.
This pertains to the SBC, or an engine that incorporates a wedge within the combustion chamber.
It may not apply to other types of combustion chambers.


Just an FYI on your spark plug readings.
The SBC Marine Cruiser Engine version will almost always require a dual plane intake manifold.
This splits the cylinders up with regard to what/how the carburetor delivers fuel/air to all 8 cylinders.
Upper plane supplies cylinder #'s 3, 2, 5 & 8.... lower plane supplies #'s 1, 4, 7 & 6.

You said that #'s 2, 3, 5 & 6 spark plugs were black compared to #'s 1, 4, 7 & 8.
So something may not be jiving with your readings, if these readings are a result of carburetor fuel delivery in the normal sense of things.
Perhaps you have an issue right in the cylinder itself, rather than fuel/air delivery!

.
 
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just a suggg. my buds boat ran fine at the dock. underway could not get above 2500 rpm. the problem was in the exhaust! it had deteriorated & had plugged up the transomcasting where the exhaust went to the prop. replaced the risers (they were rotted). IT RUNS FINE! CHECK THE RISERS!
 
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