timing way too retarded at high rpm. 1987 OMC cobra GM 350

[hn2704]

I set the initial timing on my 87 OMC GM 350 with point ignition to 9 BTDC at 600rpm. However, at 2000 rpm the timing is way retarded ~40 ATDC. I see lots of white smoke at the exhaust and smell gas at high rpm. I guess that because of the ignition is too late and the unburned gas escaped through the exhaust?
Does this mean that my advance timing mechanism in the distributor is bad? spring?weight? Where can i find the parts to replace them? I did all the timing adjustment with the boat out if the water. is it accurate or do i have to put it under load?
Thanks much

 

[Coors]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

89 octane is 8 degrees; the weights are auto.
Get at Autozone, Napa.

 

[Don S]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

I set the initial timing on my 87 OMC GM 350 with point ignition to 9 BTDC at 600rpm. However, at 2000 rpm the timing is way retarded ~40 ATDC.

I don't think thats even possible!!!!!! Pull the cap and rotor, and point plate and look at the weights and springs. Is anything missing, rusted up, etc.
Not even sure it would run at 40? ATDC.

 

[Coors]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

Diesling might do that......

 

[Maclin]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

Could be the timing gun sensor picking up a signal from the wrong plug wire. Each spark plug fires at 45 degree spacing after or before the ones adjacent to it, if the gun starts "listening" to the wrong plug wire then that reading would be about right.

What is the most recent history of this engine, last time started, last time it ran ok, last full tune, etc.?

 

[hn2704]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

It ran fine last summer although a little rough at the end of the season. I'm preparing the boat for this year and so far i cleaned the carb, replaced ignition wire and will replace belt and point, dist cap... I set the timing gun (snap on advance timing gun) at +30 and 2000rpm and aimed for 0 and the mark was off the ATDC scale. It ran ok at high rpm though. I will check the spring and weight and make sure that the gun won't pick up the signal from another plug and redo the adjustment

 

[Maclin]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

Is it a dial-back type of gun? Those have a dial with degrees on them, you turn the dial until the timing mark goes to zero on the engine. Then whatever the dial shows is the advance at that rpm. That is the only type I recommend using to check the advance at rpm. If it is just a static gun then you have to rely on the marks on the engine, kind of hard to tell what the actual degrees are then.

 

[JustJason]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

Diesling might do that......

How pray tell.... do ya check/verify the timing on a dieseling engine????
Dieseling is self ignition..... no spark.

 

[hn2704]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

Is it a dial-back type of gun? Those have a dial with degrees on them, you turn the dial until the timing mark goes to zero on the engine. Then whatever the dial shows is the advance at that rpm. That is the only type I recommend using to check the advance at rpm. If it is just a static gun then you have to rely on the marks on the engine, kind of hard to tell what the actual degrees are then.

It's similar to that. You have a + and - button to set the the timing . Whatever show on the display when you get to the 0 mark on the engine is your timing.
Should I check the timing under full load or on muff is OK?

 

[Maclin]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

All that matters is the rpm, load or no.

 

[JustJason]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

i bet your on the wrong wire as well.

 

[newport dave]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

How pray tell.... do ya check/verify the timing on a dieseling engine????
Dieseling is self ignition..... no spark.

Have to admit, I was thinking the same thing.

 

[Coors]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

I meant throwing weights, springs in dist.

 

[Don S]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

I meant throwing weights, springs in dist.

Oh boy, now that sure cleared things up

 

[Coors]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

OK, I meant, the dist running backwards, jumping around, etc, might loosen any suspect springs or weights.
when I inherited the mess I have, I found the weights broken off, my SIL admitted it had been dieseling at shut off.

 

[Coors]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

And that's another reason #7 cylinder was hydro-locked, and battery anode blown off, from trying to restart it.

 

[newport dave]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

OK, I meant, the dist running backwards, jumping around, etc, might loosen any suspect springs or weights.
when I inherited the mess I have, I found the weights broken off, my SIL admitted it had been dieseling at shut off.

I've never seen an engine run backwards while "dieseling". Every one i've seen still rotates in the correct direction.

I think it's more likely that the advance weights being messed up (sticking at high advance) were the cause of the dieseling, not the result. But I could certainly be wrong.

 

[Coors]

Re: timing way too retarded at high rpm. 1987 OMC cobra GM 350

I stand corrected. But the off and on, jumping around is my bet on my boat.
Never seen weights broke off at the pivot point, but who nows the history of the boat?