Logo
FULL SITE MENU

Help 1991 30 OMC Cobra

R

reganhopkins

New member
I have a 1991 3.0 litre OMC Co

I have a 1991 3.0 litre OMC Cobra It has a rough idle and when I go to put the boat up on plain it kind of jerks or hesitates. Could this be water in the gas?. Does anyone know the location of the idle screw on this engine?. Also when the boat is stoped and in idle what should the RPMS read?

Any help would be appreciated.
 
"idleing in gear the rpm,s sho

"idleing in gear the rpm,s should be around 700 rpm's yes it could be water in gas or it ay just need a good tuneup. need to know alitte more about your boat to give futher advise. also do a compression test on the engine during the tuneup"
 
If it is a Holley 2bbl the adj

If it is a Holley 2bbl the adjusting screws are on the side of the float bowl. Screw them all the way in until they touch seat. Then back them out ¾ of a turn. The linkage idle screw is on the opposite end of the on the carb linkage. Check your fuel filter there is one right where the fuel line goes into the carb. If the boat has set for a while the rock filter will kind of crystallize with crap from the fuel. Water in the gas can also come from your dog house. Being a 91 the old inner foam can fill with rain water through the cup holders. And that water can be sucked into the carb. Most of all a good tune up will help most.
 
"Thanks for the advice Michael

"Thanks for the advice Michael and Kirk. Michael I have a timming light but no idea how to use it, I am an amature. I replaced the plugs, wires cap and rotor.

Its a 16 foot doral with a 1991 3.0 litre omc cobra.

What does the linkage idle screw do? Would adjustting that the wrong way cause my boat to caugh and sputter? Where should the linkage idle screw be set?

Is the fuel filter hard to change?

Should I be using a premium gas in my boat?"
 
"What does the linkage idle sc

"What does the linkage idle screw do?
The linkage idle screw will set the idle after you set the card up right. One way will increase the idle the other way will decrease it. Make sure the engine is warmed up and the choke is fully opened before setting it. The idle screw will only increase or decrease the RPM’s when at idle.
Have you checked you float level? If it is running sloppy you might need to adjust your float. There is a button size screw cap on the side of the float bowl. Without the motor running remove it. While looking at it shift your body weight to rock the boat one time and see if the gas laps out over the threads. If not you will need to adjust the float is to low. If when you remove the screw cap and gas pours out the float is too high. The adjusting screw is on top. Loosen the bottom nut which will allow you to turn the center screw for adjustment. Go a little at a time always checking the sight hole and when the gas just starts coming over the threads set it by tighten the bottom nut.
When changing the fuel filter it is best if you have a line wrench. They are cheap and well worth it. The give you equal pressure on all sides of the nut and helps stops twisting the steel line. Use two wrenches, one on the carb nut and one on the line nut.
I have the same motor and I burn regular unleaded gas.
I hope you get it running. Nothing sucks more than looking out the window at you boat on a beautiful day wishing you were at the lake."
 
Back
Top