Absolutely frustrated with this Mercruiser engine

Stee6043 said:
I think we're all starting to get a complex from you continuing to refer to our 90's boats as antiques...:)
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That's funny I just spent 8 hours on the water yesterday thinking the same thing. I believe that's why most of us continually upgrade our electronics since they go wonky and stop working. Long ago I had Navman displays. When the displays got wonky, they went out of business. I have a Standard Horizon CP1000 Navigation display which has started to reverse the image from time to time and of course they have gone out of business. Same thing with Floscan.

I believe that expecting anything electronic to last 25 years is a big ask. No question that some products are better than others but even my Raymarine displays gave out along the way with the Norcold refrigerator and the microwave.

Part of owning a "classic" (I will adjust my vocabulary). :)
 
PlayDate said:
That's funny I just spent 8 hours on the water yesterday thinking the same thing. I believe that's why most of us continually upgrade our electronics since they go wonky and stop working. Long ago I had Navman displays. When the displays got wonky, they went out of business. I have a Standard Horizon CP1000 Navigation display which has started to reverse the image from time to time and of course they have gone out of business. Same thing with Floscan.

I believe that expecting anything electronic to last 25 years is a big ask. No question that some products are better than others but even my Raymarine displays gave out along the way with the Norcold refrigerator and the microwave.

Part of owning a "classic" (I will adjust my vocabulary). :)
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that's hilarious. I too had the Navman 3100, and the CP1000 (mine would go upside down and backwards). I actually fixed that one a couple of times before giving up, and putting in an A95. But, my RL80CRC and radar actually still work.
 
Got the new used ECM installed today and it made no difference in the performance of the engine. Also tried running it in maintenance mode with a jumper. It ran a little worse is all.
IMG_5705.jpeg


Engine Idling:
IMG_5706.jpeg


1st engine run at full throttle:

IMG_5707.jpeg

Second engine run at full throttle:
IMG_5708.jpeg

Third engine run but stopped pushing throttle forward once 2000 RPMS were met:
IMG_5709.jpeg
 
Wow......
Two things is all I can think of
Do a complete leakdown test on the engine then a compression test. Reaching but is there still a valve issue??
Put a scope on the injectors and verify the data is actual on the injector.
 
Is it kind of suspicious that the manifold absolute pressure and the barometric pressure are so close in the video it sounds like something mechanical is holding the boat back very interesting. . Maybe a possible vacuum leak when the intake was put on just trying to throw out ideas
 
Really had my money on the ECM. I'm still thinking something electronic. Many years ago I had a friend with a fuel injected 454 Merc. It had a similar performance problem where it seemed to run fine, but was down on power. All of the obvious and a ton of not so obvious stuff was eliminated. A very wise and experienced marine mechanic said, "Unplug the tach and run it again. Sometimes a bad tach causes problems with the ECM." Nobody took the suggestion seriously, but eventually tried it because it was so easy to do. Well, guess what? That was the problem.

I would also try running with a way smaller prop. If it is mechanical, there should be at least some increase in WOT RPM.
 
Scott215 said:
Is it kind of suspicious that the manifold absolute pressure and the barometric pressure are so close in the video it sounds like something mechanical is holding the boat back very interesting. . Maybe a possible vacuum leak when the intake was put on just trying to throw out ideas
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When I first changed the ECM it showed a Code 33 for a faulty MAP sensor. I cleared that as I thought it might be something from its prior life. The code did not show again during the test runs.
 
Scott215 said:
Is it kind of suspicious that the manifold absolute pressure and the barometric pressure are so close in the video it sounds like something mechanical is holding the boat back very interesting. . Maybe a possible vacuum leak when the intake was put on just trying to throw out ideas
Click to expand...

When I first changed the ECM it showed a Code 33 for a faulty MAP sensor. I cleared that as I thought it might be something from its prior life. The code did not show again during the test runs and I had recently replaced the MAP sensor.
 
Hopefully these are intact, or you have been replacing them when re-installing the plenum.
plenum gaskets.jpeg
 
This is getting more interesting by the day
 
Map should be around 10 psi at an idle with good vacuum from what I've read and been told
 
Is the spark advance normal? 17deg at idle seems like a lot - as if the base timing is off.
 
Manifold absolute pressure
 
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