94 force 90 hp, very high idle!

[fattypackard]

1994 sportjet force 90 hp engine....

so a few weeks ago, i couldnt get the engine to fire. after checking compression...spark, etc etc it came down to the carbs.
so i got some rebuilt carbs and threw them on.

i put the boat in the water today to test them out. the engine fires and then idles extremely high! it basically sounds like the engine is running at full throttle.

ideas, tips on what to check? i messed with the idles screws on the sides of the 3 carbs....but that did not affect it at all.

what else can i check?

TIA

 

[fattypackard]

Re: 94 force 90 hp, very high idle!

also, where is the idle speed adjustment screw on this engine?

 

[pnwboat]

Re: 94 force 90 hp, very high idle!

Idle speed adjustment screw is on the vertical tower shaft. It has a lock nut to keep it locked in place. See Item 4 in the diagram below.

http://www.boats.net/parts/search/Merc2/Force/90%20H.P.%20%281991-1994%29/0E000001%20THRU%200E093699/TOWERSHAFT%20AND%20THROTTLE%20LINKAGE%2091E%20THRU%2092C%20E000001%2CE009499/parts.html

 

[Maxum21]

Re: 94 force 90 hp, very high idle!

i had a '93 force 90. i could never get it to idle perfect... you need to figure out why it all of a sudden started idling high. maybe something sticking in the carb

 

[fattypackard]

Re: 94 force 90 hp, very high idle!

thanks for the replies!
i will look for the tower shaft/ screw tomorrow.

the carbs were just rebuilt...shouldnt be a carb issue....

and i know the plastic throttle linkage ends were lengthened out for some reason....so i will shorten that tomorrow and see if it help.

 

[fattypackard]

Re: 94 force 90 hp, very high idle!

ok i adjusted the linkage and it idles great now. thanks for the tips!

 

[pnwboat]

Re: 94 force 90 hp, very high idle!

Look inside the mouth of the carbs. The throttle plates should be closed all the way at idle. If not, then either the idle speed screw is too high, or the throttle linkage to the carbs needs to be adjusted.

You mentioned the throttle linkage was lengthened out. That will open the throttle plates. That could be your problem.

 

[fattypackard]

Re: 94 force 90 hp, very high idle!

yea, it was the linkage. i got it running perfect now. thanks!


also, one other question i have is....what is a GOOD compression for the cylinders?

mine are...#1 - 120 psi....#2 - 118 psi....#3 - 118

that should be good, correct? or should the compression be around 135...?

EDIT: engine was cold when i got these numbers....so when warm they may be higher, correct? so i am guessing the compression is good....

 

[roscoe]

Re: 94 force 90 hp, very high idle!

good numbers, nice and even

 

[JAKER95XR]

Re: 94 force 90 hp, very high idle!

I have a 96 sport junk and ive had all kinds of idle,running problems.One big thing is the daisy chain fuel vent.They clog very quickly.I used the best oil from quicksilver but they still clogged every month or so.Im going to switch to walmart brand Ive heard on other threads that its good stuff.GOOD LUCK WITH YOUR SPORT JUNK