Setting Timing on GM 2.5 L

[imported_Wesley]

I have a GM 2.5 L in my boat.

There is no timing strip on the timing chain cover. There is just a notch on the pully and co-ordsponding pointer. But no guide marking the degrees.

How many degrees should I set the timing on this motor? Also what is the best way to make a guide? Using a protractor?

Thank you for your help.

 

[bruceb58]

Re: Setting Timing on GM 2.5 L

Best thing to do is to purchase an advance type timing light. You set the knob on the light to the # degrees you want and then match up the marks.

 

[imported_Wesley]

Re: Setting Timing on GM 2.5 L

Best thing to do is to purchase an advance type timing light. You set the knob on the light to the # degrees you want and then match up the marks.

How many degrees though for this motor (GM 2.5 4 cylinder)??

 

[Don S]

Re: Setting Timing on GM 2.5 L

Without a Make (OMC, Mercruiser, Volvo, etc) Model, and year, it's impossible to say for sure.

 

[imported_Wesley]

Re: Setting Timing on GM 2.5 L

Without a Make (OMC, Mercruiser, Volvo, etc) Model, and year, it's impossible to say for sure.

1985 OMC. Does the timing vary from Merc to OMC? I did not know that.

 

[Don S]

Re: Setting Timing on GM 2.5 L

Yes it changes,I can't tell you about an 85 OMC, but the 86 OMC 2.5L engine was 1°ATDC with 86 octane fuel, and 4° BTDC with 89 octane. Mercruiser 85 and newer 2.5L engines were 8°BTDC, no octane difference.
That is why I ask.

 

[imported_Wesley]

Re: Setting Timing on GM 2.5 L

Yes it changes,I can't tell you about an 85 OMC, but the 86 OMC 2.5L engine was 1°ATDC with 86 octane fuel, and 4° BTDC with 89 octane. Mercruiser 85 and newer 2.5L engines were 8°BTDC, no octane difference.
That is why I ask.

The boat us an 84. I am not sure if it is the original motor. I think it is. I have looked for casting numbers everyone on the motor. I cannot confirm it. It has points and condenser. Assuming it is an Original '84 OMC 2.5 L, do you think it would be 1degree ATDC? I don't want to advance it too much and overheat anything. So what would be a cautious setting? 1-3 degrees?

Thank you for your time

 

[Don S]

Re: Setting Timing on GM 2.5 L

I don't have any info on 85 and earlier OMC, I also wouldn't automatically assume the specs are the same as an 86 (Note, the 86 was a Cobra drive, the 85 and earlier was a stringer).
If no one here knows the proper specs, then the best thing to do would be buy a service manual so you have the proper specs. I assume you have already set the dwell on your points, since that needs to be done before setting the timing since dwell effects timing.

 

[imported_Wesley]

Re: Setting Timing on GM 2.5 L

I don't have any info on 85 and earlier OMC, I also wouldn't automatically assume the specs are the same as an 86 (Note, the 86 was a Cobra drive, the 85 and earlier was a stringer).
If no one here knows the proper specs, then the best thing to do would be buy a service manual so you have the proper specs. I assume you have already set the dwell on your points, since that needs to be done before setting the timing since dwell effects timing.

Yeah I just tried three different places to grab a manual today. No one has stock, I have to order one in for Monday, so I may as well buy it off amazon.

I was just hoping someone would know on here.

Yeah it's an OMC stringer drive '84. I do need proper specs. I don't want to guess. I guess I will install the motor today and then wait until Monday to set the timing once I get the manual.

In case anyone has the info I'd be greatful.

Thanks for trying Don.

 

[cobra 3.0]

Re: Setting Timing on GM 2.5 L

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