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Timing Cover Missing Timing Marks

troym

Advanced Contributor
'97 5.7L, 2bbl mercarb, Thunderbolt V, Alpha-I (Gen II).

Went to check the base mode timing prior to setting the idle mixture and speed and discovered the timing mark tab missing. There aren't any signs of one ever being there. But it's not immposible that it was broken off and painted over, or may have never been there in the first place. The engine is a reman short block that was installed before I bought the boat. Lord only knows where the timing cover really came from. I never tinkered with the timing before this.

By rough Eye-ball method, the base timing looks to be close to where it ought to be. But with the information in the merc manual and existing condition I have, I really don't have any way to make sure it's right on. I went through the idle speed and mixture adjustment assuming the timing was right, but I couldn't keep the engine running below about 750rpm using a shop tach. My gut instinct is the base timing is off.

Question is: Should I replace the timing cover with one that has the timing reference marks, or is there any other way to get it dialed in?
 
If this step was eliminated during the over-haul, it may indicate a low level of skill on behalf of the person who assembled the engine.
And since ignition timing, and particularly TAT (total advance timing), is so critical on our marine engines......, you'd best find actual TDC for # 1 cylinder!

Add-on timing tabs can be purchsed and installed....., but these are only as good as the balancer marking is! If the balancer outer section has slipped, then you need to know this! Again, this goes back to the person who assembled this engine!

I'd be doing a Positive Piston Stop procedure, and start fresh!
It is not all that difficult or time consuming to do!

You can build your own PPS, or buy one ready made from Comp Cams, or ___!

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Next, you need a good degree wheel, and a make-shift pointer!

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You can Google info on the procedure.
Basically, you are using two "knowns" to find one "un-known"!
It's just geometry and math!

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