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I just had a fresh powerhead put on my 2001 low time OX 66…

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I just had a fresh...
I just had a fresh powerhead put on my 2001 low time OX 66 250. Starboard motor has 720 hrs. port had same. Now new powerhead wont spin up with similar authority as the older starboard. In fact though over propped both motors ran at 5200 trimmed and max throttle prior to new powerhead. new head only spins up to 47 unless I firewall the starboard throttle which then drags it up slowly to 4900 or 5100 if I trim it too high. bstarboard motor still goes to 5300 with little concern. fuel system checked, all settings on throttle body checked and reset. it just dogs up to 4700 unless I drag it up to 5000 with the starboard motor. thoughts. compression? mechanic trying to convince me its a new motor. It has the 10 hour break in done with proper oiling. New motor should run better and faster than old one! in my humble opinion. Help appreciated.
Submitted: 3 years ago.Category: Boat
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Answered in 17 minutes by:
6/25/2015
Marine Mechanic: Joe, Marine Mechanic replied 3 years ago
Joe
Joe, Marine Mechanic
Category: Boat
Satisfied Customers: 7,580
Experience: ASE, electronics, Marine mechanical and electronics, pwc, wiring, all around repair tech,
Verified
Hello,
Thank you for allowing me to assist you, my name is ***** ***** I will be happy to assist you with your concern today.
The fact that the motor will spin up higher but takes feathering usually says the problem is fuel or ignition, other related vs actual mechanical failure of the engine, however with that said your saying it still will not achieve full rpms which the very first thing I would do is check engine compression. Preform a leak down test and then if those are good move on to checking ignition system correct timing, no misfires, receiving correct voltage, then moving on to checking fuel, pressure, checking throttle position of tps, things like that. Also know that an engine once proper broke in will develop more and more power as it breaks in more.
It also depends on how break is was preformed, but again the tech should be able to check that via diagnosis of the problem.
Another thing to do is test via a portable fuel tank to eliminate external fuel source problems.
Thank you!
- Joe
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