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2005 Mercury 75hp 2 stoke, only getting 3000rpm Max Rev at Full throttle

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FredTollenaere204

New member
Hello everyone, I took my boat out for the first time this weekend. Boat started great with no issues, after doing a lap around the lake i accelerated to full throttle. The tach maxed out at 3000rpm, normally i hit 5000rpm full throttle. Boat has fresh gas and oil. I removed the carbs to clean and inspect, all carbs are clean, i also cleaned out the fuel filter. I noticed that the top cylinder spark plug was very clean, the lower 2 plugs were oily/dirty. Has anyone ran into this issue? Thanks!!
 
I have the exact same issue I have a 2006 150 Optimax. Won't go above 4300 rpm. Starts idles perfect. Runs normal other than lacking power. Seems like its only at 3/4 throttle. Had looked at by local shop and they checked compression was good. They found fuel line issue and replaced the fuel line and fuel water separator. Replaced spark plugs. Verified throttle is opening 100% WOT. Just has trouble getting out of the hole and running at top speed. Other than that runs perfect. Very frustrating!!!
 
Thanks for the reply! Ive checked all the fuel lines for leaks, i have not found any at this point. Also i don't think my motor has a water/fuel separator. I'm gonna replace the spark plugs this weekend to see if there is any change. The spark plugs were replaced last year..
 
How to Diagnose Injector or Coil Fault on a Mercury Optimax 150 HP Outboard Engine
You tube this might be your issue. I'm going to check tonight!! Keeping my fingers crossed!!
 
I check my engine tonight and found a dead coil. Just by unplugging coil and listening. All other cylinder dropped when unplugged but this one did not!! Sounds like you may have the same issue but I suspect you have two dead cylinders. Your engine should run 5600-5700 all day long. Please do yourself a favor and don't stop if you find one. You may have two!! Let me know what you find
 
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