OMC 4.3L - Engine running poorly

[JTHall]

I purchased a 1988 20ft Four Winns with a 4.3L OMC engine in Dec. 04. The Marina winterized and summerized ( new spark plugs) the boat before I put it in the water. The engine had a 1/2 tank of gas and I filled it up the tank before I put it in the water. The engine will start but only at full throttle and after 20-30 seconds of cranking (I've since put in a new battery). The engine will not idle and it runs very rough. Once underway it has limited power even at 3500 rpms. I changed the Fuel/Water seperator filter and I have added a 4 ounces of Fuel Stabilizer because I thought there might have been water in the fuel.<br /><br />Thanks in advance for the help!

 

[tommays]

Re: OMC 4.3L - Engine running poorly

i would recomend that it gets a compleat tune up with all new parts,points if you have then cap rotar ect<br /><br />water is just hard on these parts and there really every spring items to run good<br /><br />the motor should really start within a few seconds when things are good<br /><br />have you had a boat with a choke before ?<br /><br />with the motor OFF you can remove the flame arrestor and see that the choke is closeing and that the accelerator pump is pumping gas when the throttel is moved<br /><br />DONT RUN THE MOTOR WITH IT OFF<br /><br />its hard to go from a modern efi car to a boat that does things the old way<br /><br />you need to give the throttel a few full pumps to set the choke and pump some fuel to allow the motor to start<br /><br />you will have to find a spot around 1500 rpm to allow it warm up after it starts<br /><br />tommays

 

[Lou C]

Re: OMC 4.3L - Engine running poorly

You may need to go further with the tune up. These motors have points and condenser ignition and they need to be maintained as well. If the points are bad it won't run well. With a boat that age the carb may need to be re-built as well. On mine I had tuned it up but it still ran poorly. Took it to the shop to let a pro look at it and he wound up replacing the anti-siphon valve on the gas tank (not allowing enough fuel flow) and rebuilding the carb (water in gas). After that it ran much better. <br />Another thing that can cause bad running is if the ESA system is engaging when the motor is in gear, often caused by a sticky transom shift cable. That needs to be checked by an OMC trained shop.<br />Like Tommays said starting these old carb marine motors is not like a modern car. Mine with a cold motor I give it 3 full throttle pumps, then set the throttle about 1/4 open from neutral, and then crank it over, usually it will start, sometimes I have to pump it slightly when cranking it to get it to fire. Then keep it running about 1500 to warm up. After that it starts instantly all day long.<br />BTW, I have the same boat and motor as you!

 

[JTHall]

Re: OMC 4.3L - Engine running poorly

------------------------------------<br />have you had a boat with a choke before ?<br /><br />with the motor OFF you can remove the flame arrestor and see that the choke is closeing and that the accelerator pump is pumping gas when the throttel is moved<br />-----------------------------------<br />"" I will check out the choke and accelerator pump ""<br /><br />I plan on having an OMC Mechanic look at the engine and getting a tune up.<br /><br />This is my second Four Winns - I also own a '90 19 foot Freedom which is in the repair shop having the Outdrive (bellows) repaired.<br /><br />Thanks for the advise!