175 hp merc loss of power

"This is an older 18 ft. range

"This is an older 18 ft. ranger boat with a black max 175 hp merc(s/n4588041).The boat starts and runs great with the muffs on.In neutral the rpms will top out about 3500to 4000.In forward gear it will rev. 6000 to 7000 rpm no problem.It sounds great and full of power.When I put the boat in the water it idles ok but when I try to go faster it boughs down,maybe 2000 to 3000 rpms max.A few times it sputtered and then took off but only breifly.Then it boughs down.The boat was parked 5 years before I bought it.I think it was parked because of this power problem.I have been working on it for two summers now.I've gotten alot of good tips from reading other discussion on this forum. I have seen hints of what this engine can do but only breifly.Here are some of the things I have done.
Spliced new wire going to the trigger.
Replaced one bad coil.
New plugs.
Changed vacume lines that run from carbs to cyl.
Cleaned out both gas tanks.
New diphram in fuel pump.
New bulb for gas.
Removed and cleaned carbs.
New poppet valve.
Compression is good.
Also looking for somthing showing where the vacume lines go.Year of this motor? How to link and sink carbs.
Sorry for the book. Any thoughts or suggestions would be appreciated.Thanks Randy"

I sure hope you are not reving

I sure hope you are not reving that motor up to max out of the water. You are inviting a major disaster. I highly recommend you get a manual (factory manual is the best). This will show you where the vacum lines go and also give you the procedure for doing a link & sync. Its important that you do it in the steps they give.

Do you think the vacume lines

Do you think the vacume lines or link & sink could be the problem?

Is there a way to check for po

Is there a way to check for power other than launching boat?

Stator failures and other ign

Stator failures and other ign problems are common on these. You may need a lot more that just a coil.

"How do you bleed the trim to

"How do you bleed the trim to get the engine up ,I have a Merc 175 blk max . all I get is a clicking sound ! the engine starts up But I can't get the engine up to transport . Iv'e banged on everythig But no can do . any suggestions ?"