1989 OMC Cobra 5.8 reverse problem

[smellyskelly]

Hi, my friend has a 1989 Bayliner 2455 with an OMC 5.8 Cobra. Engine starts fine from cold ( but does hunt a bit on the idle between 550 and 1000rpm!) as soon as reverse is selected she stalls and cannot re-start with putting fuel into carb first. She works fine going forward. <br /><br />There is an electronic management system of some sort which the fwd/rvse cable operates. If this is disconected she works fine in reverse and fwd.<br />Is this box faulty or can they be adjusted? Or is there another problem maybe? Would appreciate any info anyone may have to assist us. Thanks<br /><br />Scott

 

[Mod2]

Re: 1989 OMC Cobra 5.8 reverse problem

Moving to I/O forum.

 

[DHPMARINE]

Re: 1989 OMC Cobra 5.8 reverse problem

Hi! Almost hate to jump into this one,but what the ...<br /> Cobra shift problems can be difficult.The first step is to get that idle stabilized,at least 750 or below.<br /> Could also be a stiff control cable or linkage going to the outdrive.With motor off,disconect this cable and shift outdrive manually.Have someone turn the prop shaft while you do this.If it is hard to move the cable,you have to find and repair the resistance.Usually it's the cable,sometimes the linkage.<br /> I wish you good luck,maybe someone over there has the 'Talent'to help you solve this problem.Normally if you just leave the "electric management system" disconnected,you will need a new set of gears in your drive.$600.00 parts plus labor.<br />DHPMARINE

 

[rodbolt]

Re: 1989 OMC Cobra 5.8 reverse problem

hello<br />yep what DHPmarine said plus if you suspect the cable inspect it carefully. if its black change it to the new red one. the cables only last 4 or 5 years anyway. if it takes more than light two finger pressure to move the dissconected shift to transom cable then its to stiff. you must have some one rotateing the propshaft while your testing and the cable must be disconeted from the shift crank at the riser.<br /> does your engine have one micro switch or 3? we had a lot of problems with the shift bell crank in the gimbal housing getting sticky and causing this as well. the "box" is for shifting from any in gear to nuetral position. the clutch dog and gear engagement lugs are cut with a reverse draft angle so that they lock together. the "box" disrupts ign to take the load off the prop shaft and allow the clutch to disengage from the gear. its not rocket science and I have never had a problem with them but if you dont know why and how it works it will put a whoopen on ya.<br /> good luck and post me back if ya need more info. there is a lot of bogus info to be found so be careful.

 

[DHPMARINE]

Re: 1989 OMC Cobra 5.8 reverse problem

Rodbolt,<br />I reread my post and yours.Something occurred to me.Doesn't the shift interrupter circuit only cut 1/2 of the cylinders?Mercruiser cuts all,but Cobra only cuts half.<br />Therefore I don't think my post is correct unless the motor is too sick to run on half the cylinders.<br />Obviously the problem is in shifting and the switches.But normally the switches won't kill the engine.<br />What do you think?<br />DHPmarine

 

[smellyskelly]

Re: 1989 OMC Cobra 5.8 reverse problem

Thanks for your guidance guys, we'll take a look and let you know how we get on.<br /><br />Thanks again<br /><br />Scott

 

[seahorse5]

Re: 1989 OMC Cobra 5.8 reverse problem

The Cobra shift interrupter circuit varies the timing on all the cylinders to make the motor run rough when shifting out of gear. If an engine is idling too slow, or not in good tune, the motor may "kill" if the interupter is held "on" for too long due to misadjustment or corrosion.<br /><br />Like the others said, 99% of the time, there is stiffness in the cable to the outdrive, corrosion in the bell housing shift linkage, or corrosion seizing the gearcase shift shaft wiper and oring to the shift rod.

 

[rodbolt]

Re: 1989 OMC Cobra 5.8 reverse problem

hello<br /> yep. the school said it disrupts the ign . another book said it scattered the spark. there are a couple of update boxes out and I have no clue which one you have. its already been established that the motor is in poor running condition because it was stated that the idle was not stable. but if it will shift fwd and go but stall in reverse it also has a cable shift problem. could be overstroke switch failed could be one of many things.with a merc it cuts all cylinders with the OMC its supposed to idle about 450 rpm. but not all motors can run at this speed for any lenth of time and if you open the throttles they may try to die. so you have at least 2 problems to chase. I would do a complete test and tuneup of the engine starting with compression test and spark test. you have been given some excellent advice by seahorse and DPHmarine. get a manual and carefully read the section on how and why the interrupter and overstroke(if you have them) switches work.<br /> good luck and keep posting

 

[clanton]

Re: 1989 OMC Cobra 5.8 reverse problem

There is web site with all info needed to make this thing shift, includes service bulletins and history of Cobra. Someone that has the site numbers will post them. The shift cable should be red.

 

[Boatin Bob]

Re: 1989 OMC Cobra 5.8 reverse problem

Here is a link to Stuart's Cobra site Stuarts web page