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Timing for 1988 OMC 5.0 2 barrel carb

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svendaawg

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Need Timing Specs for my 1988 OMC Cobra.
I have the manuals for 1987 and 1989 OMC but not one for my particular motor which is 1988 OMC Cobra 5.0, 2 barrel carb Engine # 502APRGDP. Each manual differs in the timing specs for the 5.0 and neither gives the spec for 2 barrel carb (no sure it matters) One manual 86 or higher octane at 10 degrees BTDC . The other manual specs 5 degrees BTDC for 86 octane and 10 degrees BTDC for 89 octane. I typically run the standard unleaded 87 octane. am I over thinking this. Should I set the time at 10 degrees BTDC.
 
The 5 or 10 degrees BTDC refers to the BASE or Initial timing.
We fire up on and we idle on BASE advance, and that's it.

More importantly will be what the Progressive and Total Advance are doing.


With the standard GM SBC build (GM style Full Dished pistons), you will want to see no more than 28* @ 3,200 RPM.
The progressive advance will be rather linear.
More than that may cause a very destructive Ignition Induced Detonation.

You could bump this up a tad bit if you used a higher octane rated gasoline.
 
RicardoMarine said:
The 5 or 10 degrees BTDC refers to the BASE or Initial timing.
We fire up on and we idle on BASE advance, and that's it.

More importantly will be what the Progressive and Total Advance are doing.


With the standard GM SBC build (GM style Full Dished pistons), you will want to see no more than 28* @ 3,200 RPM.
The progressive advance will be rather linear.
More than that may cause a very destructive Ignition Induced Detonation.

You could bump this up a tad bit if you used a higher octane rated gasoline.
Click to expand...

Thank you for the response.
Time you go out and buy a new timing light with advance.
 
too much ambiguity in your question; try asking it a different way, with enough detail to provide clarity...
 
From your question, I am going to start at the beginning. First, you have to get the engine with the #1 cylinder at TDC with a wrench on the driveshaft nut. Turn the engine clockwise, if it runs clockwise, and feel the #1 spark plug hole with a finger or thumb and after the pressure stroke pushes your finger out, you are close to TDC. Look at the markings on the harmonic balancer and line it up exactly where you want it. Let's say 10 degrees advanced, which would be to the right of TDC on the harmonic balancer, if your engine turns clockwise. So, then you want to turn the base of the distributer to where the rotor is just hitting the number 1. It will be close enough to start the engine and get it more exact with a timing light. If your engine turns clockwise, your distributer rotor turns counterclockwise, and more advance on the distributer would be to turn the base of the distributer clockwise and less advance would be counterclockwise. To see the timing marks on the harmonic balancer better, use a silver sharpie or a white paint marker to brighten them up - mark TDC and 10 degrees advanced and get it right on it.
 
Neil,
I understand what you're saying but it's still confusing.
After 46 years. I can't tell you which direction my engines rotate without thinking it thru. I do know the vertical drive shaft in the lower unit turns clockwise looking down. So process of elimination tells me his engine turns counter clock wise when viewing from behind the boat.

Now to the original question:
"If I'm looking at the engine from inside the boat, do I turn the distributor to the right or left to get top dead center?"

The simple answer is we don't know where it is now. I'd like to think it's near where it should be but.....
Regardless of which way its direction of rotation is when in operation, which way to turn it as asked would depend on if its currently set correctly (with some amount of BTDC) or incorrectly set (to some amount of ATDC) and which way it turns in normal operation.
 
I believe he meant to bring the timing back towards TDC from wherever it may be set now. As in with a timing light in hand...
 
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