Spark plug change 290 AJ

[James Lee]

Hello, this is my 1st season with my 2005 290 Amberjack. I’m getting what I think is horrible fuel economy. So I’m going to change the fuel filters, spark plugs, cap and rotor as my initial “tune up”. I have twin 5.0s Mpi merceuisers. Anyone have any advice for changing the plugs. The engine room In The AJ is nice but the motors are very close together. I can barely even see the plugs at all. Any advice much appreciated thanks !

 

[scoflaw]

What do you call horrible? 1 to 1 1/2 miles per gallon sounds right for that boat. If the engines are running smooth and make 4800 to 5000 rpm I wouldn't mess with it.

 

[James Lee]

Thanks for reply scoflaw, I guess I’m just saying the boat is new to me. Not sure when it was last serviced etc. had survey done engine all good running great. Etc. my previous boat was a 215 sundowner single engine, 350 mag. So I’m new to the twin motor ownership. Just looking for tips on engine tune up as I want to do them now and start on a clean slate. I’m noticing the the spark plugs look really hard to get to. So just curious if anyone, preferably Other AJ owners have any tips. As far as the fuel economy. I fill up, and I go 2-3 days of normal cruising and some trolling and I’m at half tank according to my gauges. I don’t think I’ve ever gotten 4800-5000k rpm’s however. Wide open I’m getting around 4400 -4600 and up to 38-40 mph

 

[Stee6043]

I don't believe you'll be able to measurably impact fuel economy (of a big boat) with plugs, wires, caps & rotors unless your boat is running really, really horribly right now.

Swap out those fuel filters every year for sure.

Based on your comment above (4600rpm WOT) it sounds like she's running just fine?

 

[scoflaw]

His engines are 260 hp mpi's 48-5k rpm