Hello my 89' 7.4l merc ( 4 barrel) in my formula 242 sounds good at idle and over 3000 rpm. But sounds like its missing at lower rpms. However idles and starts fine . Its not at an alarming level ATM but needs to be fixed. Any ideas ? Thanks

What plugs are you running?

Don't know, I just picked up this boat. I went through a similar issue with my previous boat, but it was much worse than this one. A wire was toast. I imagine its an ignition part or fuel part. I was hoping the oddness of it only showing up in mid-range rpms someone could figure a likely culprit. I really dont want to again buy every ignition or fuel part until the problem disappears.

So, maintenance is out of the question ?

Not even going to look at the plugs for some insight ? And date codes on wires if Mercruiser wires ? Inside cap ?

I wouldn’t buy parts and toss at it I’d start diagnosing the issue and eliminating possible culprits. I’d start on the ignition side.

Maintenance is not out of the question. I just dont want to buy a ton of parts and hope for the best. The wires are mercruiser red, 2096. No idea of when they were installed. I would surely do plugs and wires. The coil looks brand new. Since the issue is only mid range rpm. I am suspicious of the fuel/carb side since that is variable depending on engine temp and demand. The ignition side I would think would show the problem regardless of rpm

your issue can definitely be a result of Ign or fuel delivery...but you have to do due diligence and inspect the obvious (resistance check the wires, inspect cap and plugs etc)

I have seen a few issues where the carb needed a heavy cleaning/rebuild as there was issue with fuel quantity as the secondaries transitioned