Mercruiser silent choice question
 

I'm having a problem with the flappers not holding vacuum to direct exhaust out the exhaust tips. I checked all compression fittings. Hooked a vaccum tester to each of the 4 actuators and all seem to be holding vacuum.

I dont know what to do to help your system, but I have heard it a lot. When I built mine, I used Bimba double acting cylinders ($25), a manual air switch and a $14 compressor from Farm Fleet (mounted under helm). I also used an over center spring set up so you only have to run the compressor to position the diverter, the spring holds it there, not air pressure. Just an idea.

another view

Nice set up! You made the entire system?

Not quite following your question.
Are you stating that you can activate you exhaust to go thru the thrull hull, but it slowly changes and goes thru the outdrive?
If so, mine did the same thing. I found the relief valve on the pump to be dirty and not sealing 100%. A simple remove, clean and reinstall fixed it.
Jerry

Try soap and water and look for bubbles.

yea, winter project in 1990, total around $100. many hrs making the oval drop leg pipe and cutting the oval hole. Still in use.

Yea, what us1fountain said is the fix for your problem, I remember reading it now.

I have a question related to the subject. If you use the silent choice in salt water, will the salt be cleaned out when you flush the engine? My silent choice only works on the starboard engine when flushing (running one engine at a time) so I do not know how to get the fresh water to run through the port side.

It wont run through the drive or the thru hulls?