no revs in a Mercruiser 5.7 carb.

[Alvaroe46]

Originally Posted by jrsick

ICM and distributor picture may tell a lot. I'm interested to see if the wires from the ICM to distributor have been spliced with new connectors. May be wrong ICM.

Could you also get a picture of the distributor rotor and the metal ring attached to the underneath of the rotor?

Hi all,

I hope you're all right. Around here in Spain - Andalucia - Malaga (state) there are very few infected so we are fine. Although here we can't work or go outside.

These pictures are from today . Here you can see the ignition module and the distributor.

This is the TB IV


The distributor:

The engine;


The coil ignition;
And you can see just on the left one connector (black and orange) unplugged... I suspect it's TB V

Many thanks

Alvaro


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[Alvaroe46]

Originally Posted by mmwjr

Can you post pictures of the module and distributor?

Hi!

I hope you're okay there.

Just in the previous post I left photos.

This is the black and orange connector that I suspect is from the tb v.




Thank you and take care

Alvaro


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[mmwjr]

Definitely TB IV, from what I recall there was 3 different generations of this system and this is the earlier design. I had a 1993 with TB IV and the module was a small triangle shape. This system doesn’t have a knock sensor.

Is the entire engine painted red? Mercruiser uses black paint.

[jrsick]

I think what's happened here is that the original Thunderbolt V ICM was replaced with a Thunderbolt IV ICM. That may not be what is causing the problem, but it is causing some confusion.
Mike makes good point about knock sensor. The TB V has a knock sensor input which affects timing, the TB IV (what you have) does not.
My recommendation is to download manual #24 and follow troubleshooting steps on page 1C-9. Pay particular attention to step where you "unplug WHT/RED bullet connector from distributor. Check for 12v on lead coming from module". No 12V reading means bad ICM.
Your problem sounds like it could be timing, and a bad ICM would be likely cause.

[mmwjr]

They also installed the TB IV distributor to work with the module. The TB V distributor have its module mounted on the side next to the knock module. Lots of unknowns here. Since it’s new to you and has this issue from the start I would perform a compression test and maybe a leak down test to get the health of the cylinders.

Limited rpm could be wrong gear ratio drive, a bad cylinder, not achieving full timing advance,...

[donald]

Mike
For your FYI my 95 5.7 TB IV has the module mounted on the distributor and that caused me a lot of confusion when I got the boat, it does not have a knock module or the wire that has to be disconnected to set the timing.
That is an older version of a TB IV.
Don

[mmwjr]

Originally Posted by donald

Mike
For your FYI my 95 5.7 TB IV has the module mounted on the distributor and that caused me a lot of confusion when I got the boat, it does not have a knock module or the wire that has to be disconnected to set the timing.
That is an older version of a TB IV.
Don

Yes Don as I said there was 3 generations, the OP has the oldest and yours is the newest. In between was a triangular shaped module mounted were the OPs is. None had a knock sensor. The TB V does electronic timing advance which is why there is a need to install the jumper to set base timing. The TB IV uses mechanical advance so no jumper required when setting timing.

[donald]

Agreed.
Do not know if you knew.
Don

[Alvaroe46]

Hi

Thank you very much for all the answers.
So my problem comes from there. Because it says on the engine cover that it's thunderbolt V. Or...the cover is for the other engine...

I think somebody painted the engine in red.


Is there a technical service where I give the chassis number of the boat and they tell me how it came from the factory?

Thanks

Alvaro


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[Alvaroe46]

And this connector? It's behind the distributor.

Thanksssss


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[mmwjr]

Originally Posted by donald

Agreed.
Do not know if you knew.
Don

Thanks

[mmwjr]

Originally Posted by Alvaroe46

Hi

Thank you very much for all the answers.
So my problem comes from there. Because it says on the engine cover that it's thunderbolt V. Or...the cover is for the other engine...

I think somebody painted the engine in red.


Is there a technical service where I give the chassis number of the boat and they tell me how it came from the factory?

Thanks

Alvaro


Enviado desde mi iPhone utilizando Tapatalk

Is it just the top of the engine that’s painted red or the entire thing? I believe you engine was original with a TB V but it was replaced with TB IV because the PO got it cheap after the other one died. I wonder if the entire engine was replaced after the old one died. How the boat came from the factory doesn’t matter as that is not the way it is now.

[mmwjr]

Originally Posted by Alvaroe46

And this connector? It's behind the distributor.

Thanksssss


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From the TB V setup.

[Alvaroe46]

Originally Posted by mmwjr

Is it just the top of the engine that’s painted red or the entire thing? I believe you engine was original with a TB V but it was replaced with TB IV because the PO got it cheap after the other one died. I wonder if the entire engine was replaced after the old one died. How the boat came from the factory doesn’t matter as that is not the way it is now.

Only the top part is painted red.
The two rocker covers and the intake manifold.

[Alvaroe46]

Hi everybody!!

We were talking about this a long time ago and I finally decided to take the engine out.
The result was horrible:
-a large number of bent valves.
-2 broken pistons.
-a cylinder head with a pore.

With all that the engine was running (badly) and the boat was sailing about 25 knots... incredible.

The engine is now assembled, rebuilt and running.

Thank you very much for all the coments and help.

[mmwjr]

Not surprised, glad you got it fixed.