Absolutely frustrated with this Mercruiser engine

Hoplite808 said:
@ttmott you keep saying there was severe water intrusion into the engine. I have found no evidence to suggest such a thing. I assume it's because of the one photo I had previously shared where I had spilled a small amount of sea water on the heads when I was removing the exhaust manifold and had the valve cover off already. The rust in that photo was from me failing to wipe it all up right away and was just surface rust. That was all cleaned off during the head job. I did not pull the cam out but I have a lifter tool and while the top end was apart I pulled each lifter out and inspected everything. I found no evidence of damage or excessive wear to any of the cam lobes or the lifters. I did have two bent push rods from the seized valves that I replaced. When the heads were off I inspected all eight cylinders and found no obvious damage to the pistons or cylinder walls. There are also no signs of any excessive blow by getting into the block either to support the idea that the cylinders are a problem. The crank turns free and easy and there did not appear to be any play or knocking to suggest that a con rod bearing or crank bearing are going bad. The oil is clean and free of metal shavings I had even cut the old oil filter apart to double check for shavings in the filter, and there were none. The oil also has never shown any signs of water contamination at all. If it were the timing chain I would expect the engine to run horribly throughout its RPM range. Instead it idles smoothly at the appropriate RPM and accelerated normally and feels normal until it gets to 2000 RPM's in gear then it just simply won't accelerate further. Which gives the boat a top speed of about 10 knots on smooth water. This project has beaten me and I'm just going to let it go for a song and the next owner can at worst case scenario repower it and still have a good deal. I've already found another boat that works and is powered by a pair of good reliable Perkins diesels to replace this with now anyways. As soon as I can sell this I can get back on the water.
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Quitter
 
Hoplite808 said:
Per J. D. Power the low retail blue book is $22,040 with the options I have installed and the suggested list price is $58,462. With the new bimini, outdrive, charger/inverter, and other electronics and a few other things do you all think it's unreasonable to ask for $22,000?
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Ask what ever you want. It is worth only what someone is willing to pay for it, regardless of what "Blue Books" say. Your ask is a stating point, as long as you are open to negotiation and how bad you want it gone.

Low blue book usually doesn't mean a basket case engine. If the right buyer comes along, OK. If not, then expect few, if any, takers. Especially the way you explained the lack of Mercruiser support infrastructure in HI.
 
I do not agree with the guys who cling on the 120psi compression .

Minimum acceptable by manufacturer for the 7.4 mpi is 100psi and not more than 10% difference between cylinders

https://www.manualslib.com/manual/1813938/Mercury-Mercruiser-Mcm-454-Mag-Mpi.html?page=289

When he has 120 on all 8 , digging in the compression numbers is surely not the answer for the mess here . Especially when you look at the video when he is not even close to plane out . Like mentioned before : even a bit tired 7.4 would push way more than what we see here.

Hoplite : when you went all the way with this engine i would try to test the last things to figure out if its firing on all cylinders under load before pulling the trigger and selling or sinking it as it is .

If it was me i would not throw any further money on it unless i know for sure what the problem is .
 
Hoplite808 said:
@ttmott you keep saying there was severe water intrusion into the engine. I have found no evidence to suggest such a thing. I assume it's because of the one photo I had previously shared where I had spilled a small amount of sea water on the heads when I was removing the exhaust manifold and had the valve cover off already. The rust in that photo was from me failing to wipe it all up right away and was just surface rust. That was all cleaned off during the head job.
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Sorry, I mentioned it once in a previous post; probably a mental carryover from someone else's plight.
 
Most of us will continue to second guess this for a long time. I am comfortable that the OP has done everything he can to make this engine work. Short of being there to actually go through everything again or replacing the engine.....I agree it is time to walk away.

Being in Hawaii just makes everything more expensive and time consuming. Someone buying the boat knowing that there is a 95% chance they have to replace the engine is a reasonable sale to the right buyer.

While I would like to know if the both injector banks continue to fire at 2,000 rpm and what a proper leakdown/compression test shows.......it is not my boat.

If I bought it knowing what has been attempted so far in this thread.......I would have planned to put an engine in it and not waste more time trying to figure it out. As to the engine.......that would depend on what I have access to. A quick review of Facebook Marketplace and on line sources in Hawaii reveals a lot of junk. That said.....someone who is in the repair business could easily buy it, replace the engine with a working truck engine and flip it.
 
Hoplite808 said:
It's not that I won't it’s that I can't. I'm by myself mostly and the issue is that I can't steer the boat while also being in the engine bay.
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You need to be a little more creative.

Buy a 30’ length of vacuum hose and run it right to the helm. You can spray the carb cleaner in while you drive.
 
It’s hard to imagine you couldn’t pay some kid to operate the boat while you inspect the engine.
 
aerobat77 said:
I do not agree with the guys who cling on the 120psi compression .
Minimum acceptable by manufacturer for the 7.4 mpi is 100psi and not more than 10% difference between cylinders
https://www.manualslib.com/manual/1813938/Mercury-Mercruiser-Mcm-454-Mag-Mpi.html?page=289

When he has 120 on all 8 , digging in the compression numbers is surely not the answer for the mess here . Especially when you look at the video when he is not even close to plane out . Like mentioned before : even a bit tired 7.4 would push way more than what we see here.

Hoplite : when you went all the way with this engine i would try to test the last things to figure out if its firing on all cylinders under load before pulling the trigger and selling or sinking it as it is .

If it was me i would not throw any further money on it unless i know for sure what the problem is .
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You'd think it wouldn't be that hard to rig 3 or 4 wires from the harness to the helm so you could test the injector firing issue (either injector bank) without leaving the helm.

'course, there are still issues/questions about the fuel supply pressure, which would be a really easy test, but that's not been done either.

And I hope that anybody that considers the boat gets a sea trial before they plunk down any amount of cash.
 
km1125 said:
You'd think it wouldn't be that hard to rig 3 or 4 wires from the harness to the helm so you could test the injector firing issue (either injector bank) without leaving the helm.
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Yes , of course you are right . In no case this is an insult for hoplite but sometimes he appears a bit helpless for an easy and free of costs test. He apoears to lack creativity and the focus how to find a solution to reach a result .
When the simplest things are a non solvable problem this will go to nowhere since there is no treatment without a proper diagnosis . At least we are down to half injectors shutting down under load or a mechanical engine issue . We will stay here until this question is aswered.
 
aerobat77 said:
Yes , of course you are right . In no case this is an insult for hoplite but sometimes he appears a bit helpless for an easy and free of costs test. He apoears to lack creativity and the focus how to find a solution to reach a result .
When the simplest things are a non solvable problem this will go to nowhere since there is no treatment without a proper diagnosis . At least we are down to half injectors shutting down under load or a mechanical engine issue . We will stay here until this question is aswered.
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Spell check is your friend.;)
 
half the injectors turning off under load? That's a new one on me, please explain.

Rebuilt injectors with a different ecm powering them.
 
scoflaw said:
half the injectors turning off under load? That's a new one on me, please explain.

Rebuilt injectors with a different ecm powering them.
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It's not really "under load", it's the issue that's been discussed MANY times prior in this thread. That the ECU is sensing something wrong and going into a "protection mode" that cuts power to one of the two banks of injectors. If the inputs into the ECU are what's causing that issue, then swapping ECUs would (should) give you the exact same results. We know there's loose unconnected wires in the harness, and none of those have been verified to have nothing to do with the ECU.

This is largely based on the observations that the problem occurs around 2,000 RPM. Now, there's a bit of disagreement on whether that's the issue limiting the RPM to 2,000, or if it's just the lack of power and the load on the boat that seem to match at 2,000 RPM. There are some that say that the engine scan shows the engine is NOT in this protection mode, but there are others that say this particular vintage of ECU doesn't even have that feature (which is disputed by a member who was actually involved in the software development of said ECU). Now you'd also have to consider that the PID being scanned for the ECU for a "protection mode" might even be different for this vintage of ECU, so we REALLY don't know if that reading on the scan tool is valid. ** One way to FOR SURE either validate or eliminate the issue is for the OP to run a test on the two circuits in question while the engine is having issues. He says he can't do that because the harness is in the engine compartment and he needs to be at the helm to run the test.

However, rethinking this, I'm wondering if he just can't do this test at the dock. That possibility seemed to be eliminated because he says he can rev full past 3,000 RPM at the dock. But can't any four cylinder do that without a load?? If his V-8 is running in (effectively) "four cylinder" mode because of some faulted condition, wouldn't it still be able to run up to 3,000 RPM with absolutely no load on it?

** EDIT - and there is a way to test if that PID reading is accurate or not by forcing a fault on the ECU and seeing if the scan tool accurately displays that the ECU is in a "protection mode", but that test too has been ignored.
 
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