1972 Mercruiser 120 Timing Help Please

[libellav15]

Hi guys

new here - and love the site - so helpful already.

the problem i am having is the timing on my 1972 Mercrsr 120.

the engine runs really nicely - but having just bought the boat fancied doing a service and tune.

At idle of about 700 the timing marks are nowhere near the required 6btdc

the 'floating' adjustable mark is about 2 inches off the guage to the left.

no vacuum advance pipe that i can see - should there be one?

any ideas - anyone else had this problem?

Thanks guys - in advance (no pun intended)

Adam

 

[Bt Doctur]

Re: 1972 Mercruiser 120 Timing Help Please

Impossable to answer without knowing EXACTLY where the piston is in relation to the mark on the balancer.Sometimes the outer portion moves a bit from the inner portion throwing the "timing mark" off but not the actual timing.Establish true #1 TDC compression stroke and verify that the mark on the balancer is at "0". A "wobbling mark" could be bad dist bushings allowing the shaft to move around when turning.

 

[libellav15]

Re: 1972 Mercruiser 120 Timing Help Please

thanks Doc

floating was a bad word. i just meant the 'non' stationary mark - ie the one on the balancer - luckily its not wobbly - lol

great advice re the front and back of the balancer slipping.

might explain why i have read so many posts of a second notch being cut on the balancer.

best way to get tdc? plugs out and spanner on the pulley?

also, can you explain how to measure dwell on the points please doc - and what is a dwell-meter and where would you expect them to be sold? i have asked 2 motor factor shops and they have both looked at me as if i had just done a big-job on their shop floor!!

cheers again buddy

adam

 

[Bt Doctur]

Re: 1972 Mercruiser 120 Timing Help Please

cant acces the link anymore but dwell is the amount of time the points remain closed to charge the coil. it`s measured in degrees. Not used on electronic systems. For the point start with the gap at .018(a matchbook) and you should be fine. every .001 difference in the point gap affects timing. .001 smaller (.017) increases the timing 1 deg. Larger .019 retards the timing.1 deg.

 

[Bt Doctur]

Re: 1972 Mercruiser 120 Timing Help Please

http://www.outboardrepairs.com/topics/013286.html

 

[fishrdan]

Re: 1972 Mercruiser 120 Timing Help Please

You can get a dwell meter at most auto parts stores, Checker, AutoZone, CarQuest, etc.

It does sound like your balancer slipped, so you will need to find TDC again with a piston stop, google it. I would check the balancer and make sure it's still running true and straight.

 

[libellav15]

Re: 1972 Mercruiser 120 Timing Help Please

Thanks to all.

sorry for the delay thanking you all - just got back from work trip.

cheers again

Adam