470 3.7 ignition timing

Dunromin

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Apr 29, 2011
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When I rebuilt my 3.7 Mercruiser, I timed it manually at 4 degrees BTDC. In the water the engine was missing, so I connected a timing light and saw it was several degrees in advance, (2" off the marks on the rotor) I retarded it, and this fixed the missing problem,
but since the distributor has no external way to lock the auto advance mechanism, how do I accurately time it, using a timing light?
 

fmalott

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Jun 28, 2010
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Re: 470 3.7 ignition timing

what year 470 i have a manual but i can't upload for some reason do you mind if i send it by email
 

stonyloam

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Re: 470 3.7 ignition timing

since the distributor has no external way to lock the auto advance mechanism, how do I accurately time it, using a timing light?

Interesting question. I guess the only thing to do is remove the cap and plate to make sure the centrifugal weights free to move, and are retracted all the way, then start it and check the timing, without advancing the throttle. full advance should be 25-29 degrees at about 2200 rpm according to the manual.
 

Dunromin

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Apr 29, 2011
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Re: 470 3.7 ignition timing

Thanks, I appreciate the offer, but I have 2 manuals, an original Mercruiser manual from the Adults only section, and a Seloc. I just can't find any reference to my question in either of them. I suspect they are intended for someone who has some level of experience, and so they skip the nitty gritty stuff they feel is obvious. As a matter of interest, mine is a 1980-82. I found a post on this site that advised removing the plugs, and spinning the engine by the starter, I imagine this will allow me to time using a timing light, at a sufficiently low RPM so the auto advance doesn't activate. What do you think?
 

fmalott

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Re: 470 3.7 ignition timing

scan0001-2.jpg

scan0002-2.jpg
 

Don S

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Re: 470 3.7 ignition timing

since the distributor has no external way to lock the auto advance mechanism, how do I accurately time it, using a timing light?

You time it at idle rpm (650-700), there is no external lock for the advance. If your advance is moving at idle rpm, then you need new springs in the distributor.
 

Dunromin

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Apr 29, 2011
Messages
58
Re: 470 3.7 ignition timing

Great, there's enough info here that I should be able to resolve this issue next time it's in the water. Thanks a bunch
 
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