1999 Mercury XR6 150 HELP??

[walker07]

Hey guys, looking for some advice on a new to me 99 Mercury XR6 150. Motor ran fine on 2 separate test trips, but not very good water pressure. Had the lower unit serviced, change impeller, changed plugs from Autolite to Ngk, and removed the Oiler system with the block off kit. Also changed the water separator filter and added fuel filter to the carbs. Now the problem, motor idles fine and smooth. Boat planes off strong, but starts losing power after boat is planed off(sometimes quickly, or within 30-60 seconds) and comes back down to idles speed. The boat will plane off again, but has the same symptoms. Choking the motor while losing power does not help at all, and still loses power? Thanks for any advice on where to start looking?

serial: OG841068

[xcoach]

Sounds fuel related, check your hose for ethanol deteration, primer bulb, and fuel pump diaphragm. That motor has 2 thermostats that open up depending on motor temp, may take a few minutes before you get a strong stream of water. Even at 5000 rpms mine is not that great and I replace my water pump every 100 hours.

[JOE54]

check out FAQ on fuel system problems

[walker07]

Update: all the electrical checks out fine, compression is good. When the boats starts missing and losing power, you can pump the bulb and the motor surges as if it wants to run. Looks to be fuel pump, primer bulb, or fuel line after water separator.(or all of the above...) will keep you posted.

[EuropeanAM]

Address EVERY item listed in the below link EXACTLY as described.

Don't skip, piece-meal, or substitute... if you do, you may be chasing the problem for a LONG time:

FUEL LINES AND PERFORMANCE PROBLEMS