1986 omc 5.0 ignition problem? Help.

[serroti]

I have an 305 OMC 1986. points were replaced with solid state ignitor kit. This ran great for a season. Now I have low voltage measured at the coil, (.9-3.5 volts). Alternator puts out a strong 16 volts. Coil is new. An engineer friend suggested that my dwell my be off, rotor shaft in distributer worn out, or both. The engine runs fine out of the water. In water under load it bogs down heavly after a few minutes of operation. This problem duplicated with old points system reinstalled. Thanks for any advice!

 

[Howard Sterndrive]

Re: 1986 omc 5.0 ignition problem? Help.

where exactly are you putting the red and black lead of your meter to come up with those numbers?

no way is it running with 3.5V to the coil.
put the black probe of your volt meter on the negative terminal of your battery. Put the red probe on the + terminal of the coil.

 

[serroti]

Re: 1986 omc 5.0 ignition problem? Help.

Hi, both leads were on the coil. I just noticed that the accel high output coil I bought last season is a 12 volt coil. Is it suppose to be a 7 volt coil?? Is that what the stock coils are? Thanks.

where exactly are you putting the red and black lead of your meter to come up with those numbers?

no way is it running with 3.5V to the coil.
put the black probe of your volt meter on the negative terminal of your battery. Put the red probe on the + terminal of the coil.

 

[MikDee]

Re: 1986 omc 5.0 ignition problem? Help.

What kind of ignitor was used? Pertronix has a dedicated Flamethrower coil to match.

 

[serroti]

Re: 1986 omc 5.0 ignition problem? Help.

What kind of ignitor was used? Pertronix has a dedicated Flamethrower coil to match.

Yes, this is what I have. Both.

 

[serroti]

Re: 1986 omc 5.0 ignition problem? Help.

Yes, this is what I have. Both.

Just measured my coil using batt. neg. I had 10.8vdc at idle and up to 12.2 at high rpm. I am I back to the dwell problem in my distributor?? Thanks for your help.

 

[Howard Sterndrive]

Re: 1986 omc 5.0 ignition problem? Help.

there's no dwell to worry about with Pertronix, but shaft play can be a problem. I've seen one rub the tape off the trigger wheel and the magnets flew out.
However, the fuel system is probably more suspect than ignition based on a bogging-under-load symptom. Check the fuel filter, then watch the choke to make sure it opens correctly, clean the flame arrester. Then compression test the motor watching for moisture on spark plugs.

 

[serroti]

Re: 1986 omc 5.0 ignition problem? Help.

there's no dwell to worry about with Pertronix, but shaft play can be a problem. I've seen one rub the tape off the trigger wheel and the magnets flew out.
However, the fuel system is probably more suspect than ignition based on a bogging-under-load symptom. Check the fuel filter, then watch the choke to make sure it opens correctly, clean the flame arrester. Then compression test the motor watching for moisture on spark plugs.

Great advice, the shaft seems to be solid, but bearing wear might be hard to tell. I believe its the orginal distrib. The water sep. filter was changed last year, and the inline filter has been changed every season. My boat mechanic thought the carb. was the problem last year so he rebuit it. Still had the same problem. I have been using fuel additive over the winter months but here in the people's republic of cal. we have been using 10% ethanol for several years. This does wonders to carbs. and seals when it sits for any length of time. The motor, by the way has only 13 hours on the rebuild. Any ideas?? Thanks

 

[Howard Sterndrive]

Re: 1986 omc 5.0 ignition problem? Help.

you need to check fuel delivery, pressure to the carb inlet should be 4-7 psi when trying to get on plane. The anti-siphon valve at the tank could be faulty.
Start with a compression test of the engine. That should be done annually as part of a tune-up and it's the 1st step of any power diagnosis.

 

[Howard Sterndrive]

Re: 1986 omc 5.0 ignition problem? Help.

and you need to confirm your ESA system is functioning properly and shift cable is adjust and functioning properly.

 

[serroti]

Re: 1986 omc 5.0 ignition problem? Help.

and you need to confirm your ESA system is functioning properly and shift cable is adjust and functioning properly.

Thanks for your continuing advice. Do you know were I can get an inline fuel pressure gauge to test your low pressure theory? I'll find and check the anti-shiphon valve also. Hopefully no compression problems with the recent rebuild. Do you know what pressure each cyclinder should be? Thanks again....