Timing Tab. Straight 6 GM 165 HP

[radair1960@gmail.com]

1973 Sportsmaster Tri-hull. 165 Mercruiser. Can’t read the timing tab on engine block. Row of teeth but I don’t know what is TDC. Straight 6 GM engine. I’m supposed to be 6 degrees BTDC but I don’t know what teeth mark that is. Right now I’m guessing 2 valleys from the bottom teeth up

 

[Bondo]

Ayuh,.... there's 1 bigger peak/ valley, that's Tdc,....

Each tooth/ valley is 2*,....

The side with more teeth is Btc,....

 

[Palone]

Put #1 cylinder at top dead center (on the compression stroke). Look at the mark on the crankshaft balancer. That mark will be pointing at 0 deg. on the timing tab.

 

[achris]

Is this what you have?

 

[Bondo]

Oops,.... it's 4* per, not 2* per,......

 

[radair1960@gmail.com]

Thanks for the great replies here. I’ll take a pic and post it. I’m gonna look for the bigger peak valley first. I’d look for #1 at compression if I knew a quick way to do that. That would certainly tell me where on the scale it is. Is there a mark on the distributor for #1? Or is its safe to assume plug wire 1 with rotor button lined up is tdc? Tab is not corroded just blank. Thanks for your engineering know how!

 

[KJM]

the tab should have numbers on it they are just really hard to see, especially if they have been painted over in the past. the mark on the pulley is equally hard to see, when you do find it mark it white with a grease pencil or something. the rotor lined up with number 1 plug wire should at least be close to tdc. at least it should bring the line/mark on the pully up close to the timing tab enough to find it. mine is exactly as ACHRIS pictured, i assume they all are. tdc is when the pulley mark is exactly in the deepest v on the tab.

 

[radair1960@gmail.com]

That’s so cool. I never thought the tab had any deeper valleys but now I know what to look for. I will mark it so it’s easier to remember. Thanks