8.1 L MerCruiser popping at 3000 rpm.. help!

Jims380DA

Member
Mar 5, 2007
286
CT
Boat Info
2000 Sea Ray 380DA, Kohler Gen
Engines
8.1L 496 MerCruiser
Hoping someone can help. Stb engine popping / stuttering at around 3000-3400 rpm. Checked fuel pressure, filters, cool fuel, etc... idles fine does not stall just can't get over that rpm range. Anyone with similar issue can point me in right direction? Thanks
 
First generation 8.1 had crank sensor issues Might be worth a check. Plug wires also
 
I had the exact same issue 2 summers ago and it turned out to be due to a failure in the coatings used in the Coolfuel fuel pumps starting to delaminate and then clog your fuel injectors. This is a known MC 8.1L failure point. Mercury will supply the replacement parts but you'll be responsible for the labor.

I would certainly start with new quality plugs AND wires as this is the cheap easy route but just be aware of the above if that doesn't solve your problem.
 
Went through this issue on an 8.1. Ended up being the injectors. Exact same symptoms.
 
Jim, If they are AC's, I had one fail at 15 hours after installation. The center electrode was gone. Popping at 3000-3500 RPM was the symptom...

Cheap fix - didn't use AC's again...

Maybe you guys are right. I'll start first with plugs. Thought they were newer, 7 years! Only 165 hours though.

Have another question. We checked fuel pressure and both engines were at around 36 lbs.... is that considered normal for the 8.1 with the newer cool fuel system? He thought in the 40s Curious
 
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Jim - has your 2000 been re-engined? My 2005 340 with 8.1's did not have CF3 which is the problematic one. I had CF2 which gave no problems...
 
Jim - has your 2000 been re-engined? My 2005 340 with 8.1's did not have CF3 which is the problematic one. I had CF2 which gave no problems...

Yes, after years of 7.4L Horizon water intrusion issues, SR and Merc Marine replaced with the 8.1L Horizons. Tech looked for paint chips that's usually issue with cool fuel. He said mine were perfect and paint not flaking off.
 
Hoping someone can help. Stb engine popping / stuttering at around 3000-3400 rpm. Checked fuel pressure, filters, cool fuel, etc... idles fine does not stall just can't get over that rpm range. Anyone with similar issue can point me in right direction? Thanks
Hoping someone can help. Stb engine popping / stuttering at around 3000-3400 rpm. Checked fuel pressure, filters, cool fuel, etc... idles fine does not stall just can't get over that rpm range. Anyone with similar issue can point me in right direction? Thanks

jim.. I’m having this same problem. What ended up being the problem. I can’t figure it out? Thanks
 

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