1999 Mercury 2 stroke 90hp idle problems

[99scout1976]

Hello I have a 99 mercury 90hp 2stroke outboard that runs great on the water hose but when I put it in the water I have to start it in the forward high idle position and then when I shift it to neutral or in gear it stalls out. When I am lucky enough to get it into gear without it stalling it runs fine. Compression is good and I?m thinking I need to adjust the idle screw but cant for the life of me find any info for idle screw adjustment for my motor. Can anyone please help me? This is my first boat and I have only been able to take it out once because of this problem.

 

[yamatech43]

Re: 1999 Mercury 2 stroke 90hp idle problems

Unless it's idling lower than 700(do you have a tach?) on hose then the problem is your carbs being trash infested....even revving a motor on a hose uses only drops of gas...in the water with backpressure and especially in gear it is under a load....clean the carbs in a soak.

 

[99scout1976]

Re: 1999 Mercury 2 stroke 90hp idle problems

Thanks for the reply Yamatech43. Would a fuel treatment do the trick for cleaning the crabs? I?m thinking seafoam? Or is an operation which requires some know how?

 

[Ballymac]

Re: 1999 Mercury 2 stroke 90hp idle problems

I never soak - some carbs are coated to protect them as they are poris. Take it completely down - and work slow. Take notes or make drawings to help you put them back together correctly. I use plain ol carb cleaner, compressed air, a toothbrush, and a very small wire. Work every inch & b throrough - and take your time. Forgot to mention- by a carb kit. Good luc,

 

[MercMan82]

Re: 1999 Mercury 2 stroke 90hp idle problems

Thanks for the reply Yamatech43. Would a fuel treatment do the trick for cleaning the crabs? I?m thinking seafoam? Or is an operation which requires some know how?

When cleaning carbs, you want to visually see that nothing is clogging it. As scout suggested, work every hole so that you are completely positive it's clean. You can't be sure with just running cleaner through it, could be a bad gasket. This way if the problem lingers, you can rule out dirty carbs and move on from there quickly determining the actual cause of the problem. Basic idea of process of elimination.

 

[MercMan82]

Re: 1999 Mercury 2 stroke 90hp idle problems

Also, you might benefit from visiting this FAQ thread here at iboats. http://forums.iboats.com/forumdisplay.php?f=31There's a post on carb cleaning instructions as well as idle needle adjustments.

 

[99scout1976]

Re: 1999 Mercury 2 stroke 90hp idle problems

Ok so I took the air intake cover off (sorry I don?t know the technical name for it) the carbs to inspect and these things look brand new. There is not a spec of carbon or anything on them. If they were trash infested wouldn?t they look dirty? Should I continue with the cleaning or look for a different problem? Thanks to everyone for the help it is much needed and even more appreciated!

 

[Texasmark]

Re: 1999 Mercury 2 stroke 90hp idle problems

Run a few tank fulls of Sea Foam at 3x the rate on the can (3 oz per gallon of gas) in addition to your regular gasoline....the engines auto oiler will fix the correct 50:1 oil mix with what's coming out of the fuel tank. After you do that, THEN think about tearing things apart if you aren't satisfied.

On tweaking the idle screws, don't mess with them until you have no where else to go. They are not something that you go around tweaking like you would on a Carter carb on your car....The service manual for that engine tells you just that....settings are CRITICAL.

Your idle speed set screw (adjusting your linkage for the entire engine via the remote control cable interconnect) just varies your engine timing,,,,,faster it is timed, the faster it idles....idle is 675 rpm and 5 degrees BTDC...WOT is 22 BTDC if set with a timing light.

You can read my posts from a few weeks back and see where I am coming from.....

Mark