I have recovered a submerged bass boat with a 75hp mercury outboard.
I have it running good above idle.
The problem is it won't idle very good at all.
I can adjust timing and mixture screws to get it to idle but it affects midrange to full throttle.
When I adjust for full throttle, I lose idle rpm.
The carbs looked clean inside other than the mixture screws looked a little worn.
Could the power pack be a suspect?

The serial number is 6503215 if this helps any. It is a 4 cyl. with a wrap around cowl.

I am a auto mechanic but have little knowledge of outboard engines.
Thanks

My reply

Click here for the first steps to follow if your boat or motor sank .

Hi, your motor is a 1984 Mercury.
If you're an auto mechanic then you know how hard it is to try to troubleshoot over the phone or web but here's a start.

Use your inductive timing light and check (while running slow and fast) EACH cylinder's spark for consistency, clamp it on each wire and point timing light at YOU and observe while running.
If spark looks consistent and regular: 9 out of 10 times switch-box, stator, and trigger are okay.

After that you need specialized meters etc. to check ignition components properly but there's a few multi-meter checks right here.

If motor went overboard [ not running] in fresh water they might be okay.
Salt water's another deal.

Timing is completely different from autos so read that section of your manual carefully and be sure you understand it before proceeding;

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