Absolutely frustrated with this Mercruiser engine

jmauld said:
I would start by pulling the injectors out and making sure they are all the same part number. If so, send them to an injector cleaning service. It’s $20-30 per injector and should be considered 10 yr maintenance anyway. The injectors “should” outlive the engines.
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Didn't he say that was done and several were shorted and not flowing then he bought new?
 
PlayDate said:
Okay....even after having a couple of drinks....trying to sort out the OP wiring without actually seeing it leads me to think I'm wasting my time. This is the standard Mercruiser used to wire the engine harness:

Black Grounds, General
Black/Brown Pump Grounds
Black/Red Voltmeter Grounds
Black/Orange Isolated Accessory Grounds
Black/Yellow Ignition stop
Black/Green Water Level Sender Ground
Black/Blue Lighting Grounds
Black/Gray Nav Light Grounds
Black/White Battery Parallel Solenoid
Brown Pumps, General, Bilge or Sump (Manually Switched)(Also alternator starter to Ign.)
Brown/Red Pumps, Bilge or Sump
Brown/Orange Power feed to Auto Bilge Switches, Pumps, Fuel/Oil Tranfer or Priming
Brown/Yellow Baitwell or Aerator
Brown/Green Fresh Water Pump/Water Maker
Brown/Blue Head Pump
Brown/Violet Washdown Pump
Brown/White Trim pos sender
Red Battery Feeds Unprotected
Red/Violet Misc. Accy. Main Feed Protected (fused) from batt to trim panel.
Pink Fuel Sender
Orange/Black Audio System Feed
Orange/Brown Electric Head, Sanitation System
Orange/Red Wiper Port
Orange Accessories common feed, Dist Panel to Acc switch, Anode Electrode, Mercathode
Orange/Yellow Diesel Preheat
Orange/Green Wiper Stbd
Orange/Blue Communications Equipment
Orange/Violet Navigation Equipment
Orange/White Wiper Center
Yellow/Black Choke Neutral saftey trans mounted
Yellow/Red Start Solenoid (starting circut), Neutral Safety
Yellow/Orange Powered Ventilation, Fans
Yellow Bilge Blowers (also alternator DC output)
Yellow/White Rudder Angle Sender
Green/Red Stop Solenoid/Kill Switch
Green/Yellow AC Grounding
Green Bonding
Green/White Engine Trim in and or tilt down
Green/Orange Engine Independent Trim down
Blue/Black Cabin Lights
Blue/Brown Oil Temp Send
Blue/Red Cabin or Cockpit Lights Port
Blue/Orange Engine Independent Tilt Up
Blue/Yellow Lighting Circuits to Remote Send
Blue/Green Cabin or Cockpit Lights Stbd
Blue Instrument & General Lighting
Blue/Violet Courtesy, Boarding Lighting
Blue/White Engine Trim Outand/or Tilt Up
Light Blue Oil Pressure
Violet/Red Eng. or Generator B+ from Breaker
Violet/Yellow I/O Trim Up (ballast bypass)
Violet/Green I/O Trim Down
Violet 12v Ignition Generator or Engine
Violet/White Trim "Trailer" switch
Gray/Black Mast Light
Gray/Red Spotlight Remote
Gray/Orange Docking Lights
Gray/Green Strobe or Beacon
Gray/Blue Spreader/Flood Lights
Gray/Violet Windlass/Winch
Gray Navigation (running) Lights, Tach. Send
Gray/White Anchor Light
White/Brown Temp. Alarm or Indicator
White/Red Fuel Alarm or Indicator ((Ignition module to Dist.)Mercury Thunderbolt Ignition)
White/Orange Fire Alarm or Indicator
White/Yellow Air Flow Alarm or Indicator
White/Green Water Press/Flow Alarm or Indicator ((Ignition module to Dist.)Mercury Thunderbolt Ignition)
White/Blue Oil Press Alarm or Indicator
White/Violet Voltage Alarm or Indicator
White General Alarm Usage, Yamaha Kill Switch
Tan Water Temp sender
Tan/Blue Warning system sense wire (Audio warning)

As you can see the White with a Red stripe is used for a Fuel Alarm or Indicator on the Mercury Thunderbolt Ignition. IF the wire is original ......it doesn't show up on the EFI or Engine wiring harness diagrams for his engine.....but I have seen the wire before on Thunderbolt distributors.

In any case if the engine starts and runs.....even poorly....my money is still on the fuel system.

Speaking of money......the OP is quite clear that he doesn't want to spend $1,000+ on injectors just because CSR says it is the most reasonable solution.

I get it......I'm guessing he bought the boat for almost nothing after the original owner couldn't make it work and doesn't want to keep throwing money at it.
Click to expand...
Thank you for posting this. Mods, this should be a sticky if it's not already.
 
So .....the white/red wire matches the amplifier wire on a Thunderbolt IV distributor. On that distributor....the amplifier is external to the distributor so the sensing wires are: white/red and white/green.

images


Thunderbolt V had a few early versions with external amplifiers but later models integrated the amplifier with the distributor (your wiring diagram does not show this wire). Why it was spliced or repurposed is a mystery. It won't start if it is a IV without the amplifier. If it is a V that wire should be dead in the harness unless someone used it for another purpose.
 
Hmmm... interesting find, John... and great detective work! :) That's not something I would have picked up on.

If the engine is truly a '96 it should definitely be a Gen V or maybe even a Gen VI.

Possibly there's a previous retrofit going on here? Hop, can you post a pic of your distributor?

Can you verify if the engine EVER ran properly? Or was this a "project" when you bought it?
 
Lazy Daze said:
Hmmm... interesting find, John... and great detective work! :) That's not something I would have picked up on.

If the engine is truly a '96 it should definitely be a Gen V or maybe even a Gen VI.

Possibly there's a previous retrofit going on here? Hop, can you post a pic of your distributor?

Can you verify if the engine EVER ran properly? Or was this a "project" when you bought it?
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I believe he got the boat as a project and attacked the heads/manifolds first which makes sense but a look at the wiring photos indicates that we are dropping into this story many chapters after it started.

The engine number is right but I'm not sure about the rest. Nobody splices wires like that unless they are trying to do something and having trouble.

In regards to the white/red wire. I have that engine harness on my boat (Thunderbolt IV) so I just needed to see if they used it on the V (which they did on some very early versions). It comes with bullet connectors at the distributor that are male and female and can be installed only one way to the harness. A photo of the distributor and the nearby harness may give us a clue as to what they were trying to do. The OP should be able to locate the white/red and white/green wires in the harness next to the distributor with their bullet connector ends. If it is a V.....they won't be hooked up to the distributor.

Still my money is on the fuel system since it starts and runs. My concern is that something else with the fuel system could also be wrong.....bad fuel or fuel contamination.....toss in a new set of injectors and the problem doesn't change.

Before I bought the injectors I would definitely pull some fuel from the fuel rail and make sure it is okay. I don't recall the OP addressed the gas issue (the boat has not been working for years).....if there was old fuel in that tank......unless you drain and flush it.....new injectors won't matter.....the new fuel will be on top of the old fuel/condensation in the tank and will not mix to fix it.
 
scoflaw said:
Post one says he flushed the gas tank and filled with new along with the laundry list of everything he replaced
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Yes....perhaps you can explain to us how he did it. For example did he drain it from the pickup tube. In that case how did he get all the old gas out? Did he do it from the filler .....again....how did he get all the old gas out? I'm curious and stopped taking people at their word a long time ago if they can't explain how they did it.
 
If the boat started with the old injectors and does not start with the new ones it must be the oil . Make sure you use 25w-40 quicksilver . Any other brand is a no start condition after replacing injectors .

Don,t believe it has something to do with fuel delivery . It must be the oil .
 
PlayDate said:
Yes....perhaps you can explain to us how he did it. For example did he drain it from the pickup tube. In that case how did he get all the old gas out? Did he do it from the filler .....again....how did he get all the old gas out? I'm curious and stopped taking people at their word a long time ago if they can't explain how they did it.
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I drained the gas by disconnecting the fuel line at the mechanical pump from the tank and attaching the hand vacuum pump I use for oil changes and spent the better part of a day pumping and pouring into red cans until the boats tank was empty. Put the fuel in my truck to dispose of it. Truck runs fine on it so fuel quality doesn’t seem to be an issue. The fuel I added a month or so ago was fresh from the station and non-ethanol. Fuel filter/water separator was then changed. Fuel pressure is holding at 37 psi at the rail even under load when it’s acting up. The new fuel injectors I got were from eBay and I paid $300 to have them and the old ones tested. Obviously the guy who tested them didn’t do it right. The SELOC manual said ohm test the injectors and if they are good they will show 12 ohms +/- .4. The old injectors all tested exactly at 12 and the new ones tested anything but. I tested both banks wiring with a test light and both banks appear to be functioning properly.
 
For those saying to get the $800 rinda tool all it would do is tell me what code the engine is throwing. The MEFI 1 computer in it from what I’ve read will offer very little diagnostic information beyond just the codes and I can already read for codes with my continuity tester. It is not currently throwing a code.
 
Hoplite808 said:
I drained the gas by disconnecting the fuel line at the mechanical pump from the tank and attaching the hand vacuum pump I use for oil changes and spent the better part of a day pumping and pouring into red cans until the boats tank was empty. Put the fuel in my truck to dispose of it. Truck runs fine on it so fuel quality doesn’t seem to be an issue. The fuel I added a month or so ago was fresh from the station and non-ethanol. Fuel filter/water separator was then changed. Fuel pressure is holding at 37 psi at the rail even under load when it’s acting up. The new fuel injectors I got were from eBay and I paid $300 to have them and the old ones tested. Obviously the guy who tested them didn’t do it right. The SELOC manual said ohm test the injectors and if they are good they will show 12 ohms +/- .4. The old injectors all tested exactly at 12 and the new ones tested anything but. I tested both banks wiring with a test light and both banks appear to be functioning properly.
Click to expand...
A little about fuel injectors -
  • All the resistance measurement on a fuel injector validates is the coil that creates the magnetic field to open and close the pintel (valve) and allow fuel to spray into the intake tract. Nothing else.
  • There are two types of coils - saturated and peak and hold.
  • Yours are saturated (based upon what you state from the manual) which should be typically between 14 and 16 ohms. These are called "high impedance" injectors.
  • Peak and hold injectors are typically between 0.4 and 6 ohms. These are called "low impedance" injectors.
  • Installing a Peak and Hold injector with an ECM for Saturated injectors will damage the ECM.
  • Because you get a proper resistance measurement on the coil doesn't mean the unit is opening and closing.
  • Typically in marine applications that sit dormant, internal corrosion will lead to injectors not functioning properly or even functioning at all.
  • There is a very fine screen filter at the inlet of the injector that will get gummed and varnished up from fuel that sits dormant for any length of time and will inhibit fuel delivery.
  • The injector spray pattern is super critical to a properly running engine. An injector that dribbles fuel into the intake manifold will foul the cylinder.

You can take it or leave it from a fellow that buys dozens of injectors a year - you need to either get your existing injectors (if they are correct for the application) into a qualified injection shop for cleaning and rebuilding like RC Injection or get new - that is NEW Mercury injectors.
 
Curious to the exhaust set up on this boat. I have had three engines in different vehicles, not boats mind you, exhibit the same symptoms: starts and runs, idle all day long and run well until put under heavy load at which point fall flat on their face and not build any more rpm's. All three had restrictions in the exhaust, no computer codes or any other issue except not having the ability to rev out.
 
Scott215 said:
God I want to figure this out and see what was wrong. It runs good to 2000 rpm then stops, something simple I hope
Click to expand...
aerobat77 said:
If the boat started with the old injectors and does not start with the new ones it must be the oil . Make sure you use 25w-40 quicksilver . Any other brand is a no start condition after replacing injectors .

Don,t believe it has something to do with fuel delivery . It must be the oil .
Click to expand...
 
ttmott said:
A little about fuel injectors -
  • All the resistance measurement on a fuel injector validates is the coil that creates the magnetic field to open and close the pintel (valve) and allow fuel to spray into the intake tract. Nothing else.
  • There are two types of coils - saturated and peak and hold.
  • Yours are saturated (based upon what you state from the manual) which should be typically between 14 and 16 ohms. These are called "high impedance" injectors.
  • Peak and hold injectors are typically between 0.4 and 6 ohms. These are called "low impedance" injectors.
  • Installing a Peak and Hold injector with an ECM for Saturated injectors will damage the ECM.
  • Because you get a proper resistance measurement on the coil doesn't mean the unit is opening and closing.
  • Typically in marine applications that sit dormant, internal corrosion will lead to injectors not functioning properly or even functioning at all.
  • There is a very fine screen filter at the inlet of the injector that will get gummed and varnished up from fuel that sits dormant for any length of time and will inhibit fuel delivery.
  • The injector spray pattern is super critical to a properly running engine. An injector that dribbles fuel into the intake manifold will foul the cylinder.

"You can take it or leave it from a fellow that buys dozens of injectors a year - you need to either get your existing injectors (if they are correct for the application) into a qualified injection shop for cleaning and rebuilding like RC Injection or get new - that is NEW Mercury injectors.
Click to expand...

Crazy thread, as are the other associated threads. That pic of the chocolate milk coated cylinder heads after the valve covers were removed was a sad sight to say the least.

May be the "Rocket man" has a suggested an extremely important check as the best first step moving forward.

You can take it or leave it from a fellow that buys dozens of injectors a year - you need to either get your existing injectors (if they are correct for the application) into a qualified injection shop for cleaning and rebuilding like RC Injection or get new - that is NEW Mercury injectors.[/QUOTE]
 
Overvolted said:
Curious to the exhaust set up on this boat. I have had three engines in different vehicles, not boats mind you, exhibit the same symptoms: starts and runs, idle all day long and run well until put under heavy load at which point fall flat on their face and not build any more rpm's. All three had restrictions in the exhaust, no computer codes or any other issue except not having the ability to rev out.
Click to expand...

I replaced both exhaust manifolds and it is otherwise stock sterndrive setup. I also changed both flapper valves in the exhaust and the outdrive also was replaced entirely with a rebuilt one. There is no indication that I can tell that the current setup has any blockage.
 
techmitch said:
Crazy thread, as are the other associated threads. That pic of the chocolate milk coated cylinder heads after the valve covers were removed was a sad sight to say the least.

May be the "Rocket man" has a suggested an extremely important check as the best first step moving forward.

You can take it or leave it from a fellow that buys dozens of injectors a year - you need to either get your existing injectors (if they are correct for the application) into a qualified injection shop for cleaning and rebuilding like RC Injection or get new - that is NEW Mercury injectors.
Click to expand...
[/QUOTE]

I replied before that the miniscule amount of oil with water you saw in that photo was due to some residual water spilling out of the exhaust manifold as I removed it. There was no water mixed with the oil inside the engine. Everything else that was brown there was a bit of surface rust which should be expected on a 23 year old marine engine. Lastly, that photo was taken before I removed the head and had it redone at a machine shop.
 
Hoplite808 said:
I replaced both exhaust manifolds and it is otherwise stock sterndrive setup. I also changed both flapper valves in the exhaust and the outdrive also was replaced entirely with a rebuilt one. There is no indication that I can tell that the current setup has any blockage.
Click to expand...

One thing that CAN happen in the exhaust that isn't readily visible, is there could possibly be an old flapper that fell apart (usually from an overheat or from a while ago) and fell into the exhaust "Y". They can be in there a long time before being noticed. This I have seen more than once on other boats. An old flapper down there can / will block the exhaust and cause problems, including possibly eating a hole through the aluminum "Y" pipe and causing a water leak. Easy to check, Take off the riser and the pipe elbow after it and look down there with a cheap borescope.
 
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