OT430752 03 xb , when I bought the boat I was turning 5800-5900 Tournament loaded with 2 people running 76.8.It has gradually slowed down over a year and a half to 4900 rpms, regardless of what prop I run. I’ve replaced the staor, ignition ecm, flowed and cleaned injectors , new carbon fiber reeds, new pulse fuel pump kit,new bleed lines, cleaned screen in fuel pressure regulator, new electric fuel pump, fuel filter, cleaned vst out, new fuel lines from engine to tank. I’m lost, any ideas?
Compression test is needed.
I would recommend that also. Might be turned sleeve if over time it slowed down.
Also, don't forget to inspect the EXHAUST TUNER (see FAQ Section).
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
I checked the compression recently, if I remember correctly, it’s was like 125 on all 6. If a sleeve turned , would that show up on the compression test? I also replaced and set the tps according to the manual. I haven’t looked at the exhaust tuner, but I definitely will.
Have you verified full throttle yetOriginally Posted by Skintback69
No it would not, need to inspect the cylinders with a bore scope or camera. Check that exhaust system and get fuel pressure readings while problem is occurring
Thank You Leon Pugh
I have a camera, I’ll definitely check that! I also checked the fuel pressure, it was right on the specs in the manual. I have verified WOT also. It will start spinning up with the smaller prop, hits 5100, kinda jumps and drops right back to 4900.
Other item I would recommend is to install two (2) 10ga redundant grounds on the Electrical plate. One to the top right (where ground wires for CDM's are), and one to the lower ECU's Ground Cable bolt.
Carry them to the STB side of the engine and put them on the same bolt the BATTERY CABLE (Ground) attaches to.
Cheap to do... and have seen several that this resolved "phantom" problems.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
I’m having the exact same issue on mine, exactly what mine is doing. Gets to 5100 rpm and drops off 100-150 rpm and that’s the limit. 02 mercury pro xb on mine as well, I’ve went through fuel system on mine and replaced all filters, plugs, checked coils. Let me know if anyone figures this out, thanks.
Already ran the grounds to the plate also. Got the vst and injector plate off now checking everything over again. Gonna replace all the cup lines on the engine . Looked at each cylinder with my camera ,no turned sleeves . I guess I’ll send my fuel Ecm to Simonds next and get it tested .
Last edited by Skintback69; 08-07-2019 at 02:55 PM.
Agreed,I have found silly corroded engine mounted,and even pinched kill switch ground wires,and grounding bolts,caked in white powder, that a quick wire wheel clean up, made the ground contacts to the coil plate work again. All these little "free" fixes, would intermittently cause power issues.
Any luck with it? Mines still doing the same thing as well.
Did you check all the throttle blades are parallel at WOT. I know I have had to go back and double check and adjust mine when I first got it used. The secondary butterflys were not opening all the way
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