mercruiser120 Timing

[mercruiser user]

I set engine Mercruiser 120 S/N 6918374 at TDC on comp stroke mark lines up to zero, put rotor facing forward turned it 1/8 CCW to point toward #1 and the timing is 2 inches to the left of 8 deg, rpm 900 lowest I can go on muffs without engine quitting , tried 3 times with same result compression seems within limits of merc manual, any advice would be appreciated

 

[Don S]

Re: mercruiser120 Timing

I set engine Mercruiser 120 S/N 6918374 at TDC on comp stroke mark lines up to zero, put rotor facing forward turned it 1/8 CCW to point toward #1 and the timing is 2 inches to the left of 8 deg, rpm 900 lowest I can go on muffs without engine quitting , tried 3 times with same result compression seems within limits of merc manual, any advice would be appreciated

Not sure what you are saying, but you set the timing with a timing light and the engine running.

 

[Eric 3.7LX Alpha 1]

Re: mercruiser120 Timing

I am not sure... but I believe you are saying you pointed the rotor to the actual #1 cylinder on the block aka the spark plug... which is wrong...

you point it to the port on the distributor cap that is connected to the #1 cylinder.

While the cap is on the distributor, I place some tape under the cap and mark the center of the #1 post with pen/pencil on the tape. Remove the cap then you can see where the rotor needs to be pointed while the cap is off.

I think we need a little more info.. Did you remove the distributor and trying to reinstall it on the engine?


Edit... I reread your post, you have it running so are close but have to time it with a light.

 

[achris]

Re: mercruiser120 Timing

I set engine Mercruiser 120 S/N 6918374 at TDC on comp stroke mark lines up to zero, put rotor facing forward turned it 1/8 CCW to point toward #1 and the timing is 2 inches to the left of 8 deg, rpm 900 lowest I can go on muffs without engine quitting , tried 3 times with same result compression seems within limits of merc manual, any advice would be appreciated

Not sure what you are saying, ...

Neither am I, mostly because that make no sense whatsoever. How about re-posting but try some punctuation this time...

 

[mercruiser user]

Re: mercruiser120 Timing

I removed the distributor from engine, the engine was turned over while it was out, I put it back with engine a TDC on compression stroke with the mark on the engine a 0 and the rotor pointing toward #1 cylinder and its off the 8deg mark by 2 inches using a timing light

 

[Don S]

Re: mercruiser120 Timing

I removed the distributor from engine, the engine was turned over while it was out, I put it back with engine a TDC on compression stroke with the mark on the engine a 0 and the rotor pointing toward #1 cylinder and its off the 8deg mark by 2 inches to the left

I assume it's running and you are using a timing light to see where it's at, and you are looking at the marks from the front, not the side, which makes "to the left" understandable.
What you need to do is turn the distributor to get the timing mark to the right place. Make sure the rpm is at idle (around 650-700) and readjust as needed until it runs smooth. It may take some carb adjustment and idle speed adjustment. It all works together.

 

[mercruiser user]

Re: mercruiser120 Timing

yea must need a carb rebuild can't go below 900 without it quit running, turning the distributor still can't get enough movement to get to 8 deg I tried adjusting the one screw on the carb its a mercruiser carb for idle/air but just got worse engine shaking pretty bad

 

[achris]

Re: mercruiser120 Timing

This gets the dissy in to ROUGHLY the right place, enough to get the engine running. It's not the final adjustment. You take your timing light and do that, after you set the points dwell...

 

[achris]

Re: mercruiser120 Timing

yea must need a carb rebuild can't go below 900 without it quit running, turning the distributor still can't get enough movement to get to 8 deg I tried adjusting the one screw on the carb its a mercruiser carb for idle/air but just got worse engine shaking pretty bad

I give up.... What does this really say, anybody....

 

[Don S]

Re: mercruiser120 Timing

Hope you set your point dwell first. That could also prevent you from idling. Could also mean the advance springs are dead in the distributor.

 

[mercruiser user]

Re: mercruiser120 Timing

ok thanks for trying to help, l did all above as stated and set dwell to 32, took distributor apart springs look good cleaned,lubed and reassembled still the same

 

[Don S]

Re: mercruiser120 Timing

It probably is carb problems, and you really do need to get the rpm way down.