Absolutely frustrated with this Mercruiser engine

Would an incorrectly installed flapper not let the engine breath
 
Bill Curtis said:
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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Good point. You can also do the same by pulling the outdrive. For my boat's config with the Alpha Gen 2's, that's the easier route. Those elbows can be a real bugger...
 
Cars that have clogged cats don't rev up. Is it possible to put butter flys in upsidedown, I have never done them
 
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.
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I appreciate the detailed response.

I don't want to see you throw a $1,000 at it unless it fixes the problem. If you are convinced you have clean fuel, pressure and the injectors are firing.....then you are left with the injectors themselves. Yes, an electrical gremlin like a cracked distributor cap, cracked rotor or bad pickup could look like the same problem BUT when you installed the inexpensive fuel injectors......the engine would not start. Reinstalling the old injectors got it back to starting and running.

That keeps the spotlight on the injectors. I believe its time to make a choice: 1) get the injectors cleaned/repaired/replaced 2) Junk the EFI and put a carb on it.

In the end it is your money. I appreciate how frustrating this has been.
 
I'd be looking hard at option 2 at this point.

Carbs can have their bugs, but they're controllable as well as understandable. If my car still had a carb, that would suck but it's my preference for boats.
 
Scott215 said:
Scofflaw has a good point. Why start over . Many more advantages to fuel injection than carburation, period
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That's why I laid out two options. I would lean towards a carb if I was on an island where I couldn't get anyone to work on my engine because it was an ancient EFI system and I couldn't get the parts tested or fixed.

Look at how frustrating it has been for him to get anything done. At some point you have to simplify for not just this instance but for the future as well.
 
I feel the pain of the op but this thread will go to nowhere i guess.

Money and parts were thrown on this engine by shooting in the dark - in an amount that you easily would get a certified mechanic paid , including travel or hauling in the boat to diagnose and fix the real problem .

Now money is spent for nothing and we hear 'amazing' new options to convert an mpi to a carb . Sweet .

Of course nobody here can say what the correct main and idle jets would be , how an mpi designed head / combustion chamber would react to a carb , what cfm carb .... and much much more . How can we ?

Dump another fortune to find out it still does not run since the idea is as smart as trying to convert an evinrude e-tech outboard to carbs .

If ( and how should it be possible by a forum ) you do not verify if :

-the head change was correctly done
-the timing is fully correct
-the ecu is ok
-the injectors are the correct type
-the injectors are verified ok
-the harness of the injectors is ok and installed correctly

There are so many variables what or what combination of different things could be wrong that you can happily entertain the forum but you will go to nowhere.

I,m scratching my head what sane person changes e.g the heads at all if the engine starts and idles fine , compression is even and tolerable ... ?????

You need to go logical step for step or pay the mechanic before your boat is a total loss...
 
aerobat77 said:
I feel the pain of the op but this thread will go to nowhere i guess.

Money and parts were thrown on this engine by shooting in the dark - in an amount that you easily would get a certified mechanic paid , including travel or hauling in the boat to diagnose and fix the real problem .

Now money is spent for nothing and we hear 'amazing' new options to convert an mpi to a carb . Sweet .

Of course nobody here can say what the correct main and idle jets would be , how an mpi designed head / combustion chamber would react to a carb , what cfm carb .... and much much more . How can we ?

Dump another fortune to find out it still does not run since the idea is as smart as trying to convert an evinrude e-tech outboard to carbs .

If ( and how should it be possible by a forum ) you do not verify if :

-the head change was correctly done
-the timing is fully correct
-the ecu is ok
-the injectors are the correct type
-the injectors are verified ok
-the harness of the injectors is ok and installed correctly

There are so many variables what or what combination of different things could be wrong that you can happily entertain the forum but you will go to nowhere.

I,m scratching my head what sane person changes e.g the heads at all if the engine starts and idles fine , compression is even and tolerable ... ?????

You need to go logical step for step or pay the mechanic before your boat is a total loss...
Click to expand...

Nah.....its just an engine. The OP has enough mechanical skill to solve it and has done a lot of the updating necessary for a 25+ year old engine. The parts he has put on the engine certainly would have been necessary at some point in the near future.

I don't have an opinion on the heads.....if the boat sat for a long time.....that is one of the areas problems show up.

I'm also not worried if he throws the ancient EFI system into the trash. He has the skills to put a carb on it. I'll give him the jet sizes (Holley) for the primary and secondary and he will be good to go.

I think he is close.......but it will require $1,000 either way. Not having another working engine to pull the injectors out of to test ...... is one of the reasons I like two engine boats.

I just wish I had a set of working injectors to send him.
 
I'd like to reply to two things. First, I like to think I am smarter than your average bear when it comes to things mechanical. I have tools, training, and years of experience to competently perform basic maintenance and repair, as well as some complicated repair as well. I can cite all my experience if needed but it is quite a bit and I'd prefer not to. I simply don't work as an automotive mechanic anymore because I wasn't making enough money and enjoy things like eating, not being homeless, and occasionally being able to get on a boat and enjoy some time on the water. I also have the correct SELOC repair manual for my engine and posses the ability to read. I am not haphazardly taking shots in the dark and replacing random expensive parts. I perform the diagnostics prior and determine a fault in the part and then replace it but as of yet the main problem with the engine still won't remedy and all the diagnostics I perform currently tell me nothing should be wrong, but it very obviously does have something wrong. For the sake of brevity I try not to type every step of everything I've done. Its far easier and less time consuming for me to list simply what I did so its not suggested repeatedly that doing what was already done as a solution. Secondly, The carburetor modification. This would only be an option if I were to just give up and build a whole new engine. To just do a conversion of the existing block it would cost me approximately $3000.00 in parts to get everything it would need. The problem then is I would have a Frankenboat that no manual could ever help me to repair. If I'm going to redesign the wheel I'd much rather repower the thing with a diesel engine. I know a few guys where I could get a decent one for about the same price as building a whole new merc motor. I just don't want to do that, I'd rather keep it original.
 
Hoplite808 said:
I'd lik I am not haphazardly taking shots in the dark and replacing random expensive parts.
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Thats a good approach and i do not want to argue but let me again quote your own initial posting :


Hoplite808 said:
So far I’ve replaced the cylinder heads, exhaust manifolds, the spark plugs, spark plug wires, cap, rotor, distributor, ignition coil, ignition module, air temp sensor, MAP sensor, IAC, throttle position sensor, mechanical fuel pump, the electric pump in the vapor separator tank, the alternator, raw water impeller and housing , the heat exchangers, thermostat and housing, engine temp sender, oil pressure sender, the entire outdrive, and repaired or replaced wiring.
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Assuming you have basic tools like a 10$ volt meter and a compression tester changing heads , the alternator and the IAC for an engine that idles but just struggles to rev above 2000 in gear is about as useful s changing the toilet seat for your issue.

With a bit more diagnostic ( assuming you can verify its not overheating , not in limp mode ) changing tstat housing , impeller and housing is about the same.

Hard to comment you changed the entire outdrive just for this ... amazing.

I,m asking just to learn what the hell are you doing ??

I,m afraid you already have a frankenstein setup since IT IS a senseless shooting in the dark up to know .

If you want to go boating i would recommend to diagnose usefully and in future aim before taking a shot or we can go back to the carb conversion on an MPI ( since you ordered 8 injectors i guess its indeed a multiport injection , not a singleport EFI )
 
Let me throw this out (and it might be a bit mazzo to do this and if it is, someone speak up!)

Pull the plug wires one at a time and run the engine for a short period . If there is little or no change as to how the engine runs, would that not point to the injector or associated wiring or possibly something far more sinister (lifters?) associated with that cylinder ?
 
Hoplite808 said:
I'd like to reply to two things. First, I like to think I am smarter than your average bear when it comes to things mechanical. I have tools, training, and years of experience to competently perform basic maintenance and repair, as well as some complicated repair as well. I can cite all my experience if needed but it is quite a bit and I'd prefer not to. I simply don't work as an automotive mechanic anymore because I wasn't making enough money and enjoy things like eating, not being homeless, and occasionally being able to get on a boat and enjoy some time on the water. I also have the correct SELOC repair manual for my engine and posses the ability to read. I am not haphazardly taking shots in the dark and replacing random expensive parts. I perform the diagnostics prior and determine a fault in the part and then replace it but as of yet the main problem with the engine still won't remedy and all the diagnostics I perform currently tell me nothing should be wrong, but it very obviously does have something wrong. For the sake of brevity I try not to type every step of everything I've done. Its far easier and less time consuming for me to list simply what I did so its not suggested repeatedly that doing what was already done as a solution. Secondly, The carburetor modification. This would only be an option if I were to just give up and build a whole new engine. To just do a conversion of the existing block it would cost me approximately $3000.00 in parts to get everything it would need. The problem then is I would have a Frankenboat that no manual could ever help me to repair. If I'm going to redesign the wheel I'd much rather repower the thing with a diesel engine. I know a few guys where I could get a decent one for about the same price as building a whole new merc motor. I just don't want to do that, I'd rather keep it original.
Click to expand...


Then you have answered your own question. Time to send the injectors off and hope for the best.

I’m at about 90% that they are your issue but I still have some reservations specifically with the wiring and the ECM. In regards to “original”…..that boat sailed a long time ago based on the wiring and head issues.

Also, relying on a first generation EFI that is 25 years old….is asking for more financial pain. Eventually the ECM has internal issues or the wiring harness and you are back to spending really big money on it to keep it “original”.

We can respectfully disagree on a carb conversion costs. Based on what you have spent so far and what remains to be spent…….you would have been far ahead of the game financially with a carb.
 
Out of pure theory to have some fun : what parts would be needed to really convert back a mpi to a carb ?

- carb/gaskets
-Manifold/gaskets
-flame arrestor
-ignition distributor ( tb?)
-ignition module
-linkage set for carb
-flame arrestor for carb
-electrical choke module / wiring
-fuel pump
-fuel lines

What did i forgot ?

New heads , cams to match the manifold setup for a carb ?

I love carbs and i guess when you are a real pro in jetting them for optimum setups you can get a decent performance out of it , especially when nascar style fuel injection is banned !
 
Nascar went fuel injection in 2012....so. He's bought way too many fuel injected parts now to go back to Fred Flinstone era. I like my carbed old school cars and they run perfect but so do my last 5 fuel injected boats.
 
scoflaw said:
Nascar went fuel injection in 2012....so. He's bought way too many fuel injected parts now to go back to Fred Flinstone era. I like my carbed old school cars and they run perfect but so do my last 5 fuel injected boats.
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Oh , i was not aware of nascar going fuel injection , my bad .

Of course you are right in a real world , i asked the carb conversion just of theory like said .

When his list is true and he beyonds heads , manifolds, alternator and much more even replaced the entire outdrive he in fact is close to getting a slightly used 7.4 mpi in perfect running condition ...
 
It sounds so suspect that the compression is only 120 psi. Let's not forget the adjustable rockers. When you did the lash did you put each rocker on the base circle and tighten it till you have no play then a half to three quarters of a turn. Just curious it is a hydrolic roller cam correct
 
I suppose we can entertain ourselves for the next few weeks as the injectors are being serviced.

In regards to the heads and a cam.....nope. 120 psi compression won't care if it is a carb or EFI. It is an old and tired engine that hasn't run right for some time. We sit back in the contiguous 48 States and it is easy to get parts, diagnostic equipment and help. Some places that just is not true. Most people simplify when they don't have access to those things.....not double down but he owns the boat.


At least Fred Flinstone's car worked. ;)
 
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