90 hp mercury 3cyl. 2 stroke slow to get on plane

[Den H]

I have a 1987 Mercury 90hp 3cyl. 2 stroke that idles good and runs great once the boat gets on plane all the way up to max rpm which is 5500. The motor seems to be down on power off idle to about 3000 rpm. The boat is a 1987 Cheetha bass boat 15.5ft. I have checked the timing it is set at factory specs. Where is the idle air screw? My parts list shows the adjusting screw on the side of the carbs that is beside the jet vent is called the idle needle screw and the adjusting screw on the top of the carbs by the intake is called the idle air needle screw. Which one does what? Also would adjusting one of these help? Thanks for any help.

 

[mikeregas]

Re: 90 hp mercury 3cyl. 2 stroke slow to get on plane

I am having the same problem with my 98 mariner if you get any info on where or what to do let me know I would love to get my boat up on plane like it use to. I have a 16' Action Craft flats boat and it use to really jump up on plane now it drags and drags then it finally gets up on plane. I have been using my trim tabs to get on plane faster, which helps. Once it get on plane it seems to do ok.

 

[arcrat]

Re: 90 hp mercury 3cyl. 2 stroke slow to get on plane

Do not mess with screw on top... it is factory set!!!!
Try adj side screws out 1/8 turn....
Top screw is air ...
side screw is fuel...
someone sould jump in and help out , give it some time ...


arcrat

 

[Dunaruna]

Re: 90 hp mercury 3cyl. 2 stroke slow to get on plane

What are the comp readings and when was the last time the carbs had an overhaul?