I have a 2000 32 fountain fever, when I trim my drives out my port side starts to very slowly move back in and I have to keep adjusting it back. This just started happening out of the blue, can some give me an idea why.

The valve in the trim pump is most likely getting bad.

any way to test it or just check entire system for external leaks then replace and see what happens if no leaks are present?

If no obvious external leaks, then its an internal valve leaking.

Merc made a test rig to test trim pumps we have also found trim rams that were bypassing .

1 st no matter what else you move on to is check your trim fluid level with the drive completely full up position. It should be about half way full in the reservoir. If it is way low it will cause air in your system and the drive will bleed down. If your res is low there might be a possible leak and leaks can put air in the system as well even if the reservoir has a decent amount of fluid level.

Also make sure you reservoir cap vent hole is not block if you have the older cap installed. The newer caps have a better vent built into the cap. Anyways the easy stuff first to check.

Mercruser has a dual pressure testing gauge and diagnostic procedures to pin point the problem to test the valve body if it is bad. .

thank you to all, will check some things this weekend

When mine did this it was the reservoirs, they were both cracked allowing air into the system.

Here is a Bravo Service manual from 1998. Maybe it can help.

http://www.boatfix.com/merc/Servmanl/11/11covr5x.pdf