1990 3.0L OMC/Cobra rpm loss and bog

[brdmh44]

Hello guys and gals!

I have an annoying problem going on with my boat--

With two people in the boat it runs up to 30 MPH planes out and runs a little rough

With 3 or more people it won't pull enough RPM to come up on plane.

Also when returning to neutral the motor runs on 2 cylinders for 10-15 seconds then dies.

It's also hard to start when warm and struggles to pick up rpm to idle alone.

When the drive is not engaged you can rev the motor to 5,000 RPM no problem in the water

With the drive engaged it runs terible the motor shakes hard and you can hear it dropping a cylinder then picking it back up on and off.

It has great spark, good fuel supply new cap and rotor etc..

It does have a pertronix ignitor module as per points replacement. Would this have an effect on my problem?

I am not familiar with the shift interupter switch I read about- Are there any tests I may perform?

Thank you in advance for the help!

--Curious Boater

 

[brdmh44]

Re: 1990 3.0L OMC/Cobra rpm loss and bog

Anyone at all?

 

[tpl71bug]

Re: 1990 3.0L OMC/Cobra rpm loss and bog

not sure i can help as my omc 5.0 is doing almost same thing. Mine does not sound as bad as yours though. Mine will idle fine and run ok in gear but at wide open throttle bog down and sometimes stall , but start right back up. if i run it at little less than wide open it will run fine. Thought it might be the fuel filter but replaced it and still same problem. It seems to do it more when i have under a half tank so im going to start looking at fuel pump. try to look in to the shift interupter . i was going to get a electrontic ignition but havnt yet you also need to get a new esa as i understand .but there are tests i found that im probly going to be doing myself . ive found a couple of threads on here might help
http://forums.iboats.com/showthread...eengine.com/discus/messages/12488/87111.shtml

 

[brdmh44]

Re: 1990 3.0L OMC/Cobra rpm loss and bog

thanks for the info!

This has become rather annoying as the boat sat for six years and the previous owner died so I am clueless to everyone dealing with this boat.

This one also bogs under full throttle, at 7/8's throttle it runs the best if it will get there.

It feels really, really weak when you have more than 450 pounds worth of people in there.

Even with two people it still takes a bit to go up on plane.

This electronic conversion seems like a PITA on these OMC/Cobra's -- Think im going to look for a points dizzy and see if anything changes.

I'm open to any ideas!

Thanks again.

 

[tpl71bug]

Re: 1990 3.0L OMC/Cobra rpm loss and bog

heres some more . you might wanna try switching back to regular points .if you dont do the mod withthose diodes or switch the esa with the electronic ignition it can make u run bad. not sure if its all your symptoms but maybe a start if your not sure your esa replaced. i saved this one from marine engine .com. i decided to stay with points cause it did seem like a pain. i sure theres alot more guys on here that have alot more knowledge about it than me.


http://www.marineengine.com/discus/messages/12488/83999.shtml

http://forums.iboats.com/showthread...p://forums.iboats.com/showthread.php?t=343127

 

[brdmh44]

Re: 1990 3.0L OMC/Cobra rpm loss and bog

Does anyone know where I can find a list of worth OMC mechanics then? It doesn't look like I can do this alone.

Thanks!