Engine Knock on 2.5 L OMC Cobra

P

papakazoo

Cadet
Joined
Aug 24, 2003
Messages
9
1986 OMC Cobra 2.5 L<br />Has sat for 5 years. I did a lot to prepare for running(See below).<br /><br />The problem is that when engaging the drive the engine misses, shakes and knocks loudly. When idiling or in neutral it runs fine. Have run it to 2500 RPM's in neutral...sounds great no miss or knock. Only does it in gear.<br /> <br />put in new this last two weeks:<br />fuel pump - points - condensor - rebuilt carb<br />thermostat - drained / cleaned fuel tank - new gas - new fuel filters (carb & fuel pump)- new spark plugs - new battery<br /><br />Also have taken apart Lower Drive and replaced the bearings & housing (for Pinion Gear). Bought a Seal Kit and replaced Seals / O-rings all over (Lower & Upper Units). Seal was bad on water pump which caused Bearings in Pinion Gear Assy. to go bad. <br /><br />Thanks for your help........
 
N

Norm Malcosky

Seaman
Joined
Aug 14, 2002
Messages
70
Re: Engine Knock on 2.5 L OMC Cobra

Papa,<br /><br />You might try a new distributor cap. Internal spark arcing may be the cause. Pull the old one and look for carbon tracks. You might even try to clean the inside of the old one with solvent (iso alcohol)to verify if it may be the problem.<br /><br />Also check the spark plug wiring. Most use resistance wires (carbon core) that should be below 1,500 ohms per foot. This would require a multi-meter to check. A set of new plug wires would probably be cheaper - if you don't already have a meter. <br /><br />erie_guy :confused:
 
P

papakazoo

Cadet
Joined
Aug 24, 2003
Messages
9
Re: Engine Knock on 2.5 L OMC Cobra

thanks erie guy<br />i will get a new cap & wires. might be a couple of days but i'll let you know.<br />i am surprised i'm not getting more response. is this pretty wierd?
 
R

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Engine Knock on 2.5 L OMC Cobra

Hello<br /> sounds like the shift cable is sticking. check the shift cut out switch assy. if it is triggered then the motor will do alll sorts of funny things. it may or may not have an overstroke switch. if it has an overstroke switch test it to make sure it is working and adjusted properly. you may wish to test it by dissconecting the shift cutout switch and throttleing up, just be aware that without the switch you will have to turn off the engine to shift back into nuetral.<br /> good luck and keep us posted
 
You must log in or register to reply here.
Top