1989 120 hp force timing marks

[cheyenne52224]

I am trying to check my timing,I have the top dead center mark on the flywheel and then 3 more marks apprx 30 degrees further around the flywheel.When cranking at wot with a timing light i am firing just after the 3 marks pass the timing pointer.It appears to be firing a little late.I need to know which mark is the 32 degree mark,and are the marks depicting 2 degree increments.thanks

 

[bentle]

Re: 1989 120 hp force timing marks

Im pretty sure if you have an 1989 force outboard that its a 125hp instead of the 120hp you posted.
Please verify this so we can give you the proper timing sequence.
For an 89 125 force outboard the timing mark should hit dead on the 30?btdc mark at wot.
To set static time or while cranking motor you need to set it at 28? btdc mark. This is the first mark on the right of the three marks.this is static time.
After setting it then open up the throttle to wot and check again. Should be at the 28?btdc mark first one to the right of the three.
Edit. A fully charged battery is best. And make sure motor will not fire.

 

[cheyenne52224]

Re: 1989 120 hp force timing marks

Thank you,It is a 120,but it may be a 1990.It is at about 24-26 btc now,Could this be why it occasionally sneezes out the carbs when starting? It idles smooth,runs good but seems a litte punky.It has good compression,clean carbs,new surface fire plugs,strong spark.It also runs at about 4,800 RPM at wot on a 17.5 Bayliner Cobra bass boat and a 13x21 ss prop.

 

[bentle]

Re: 1989 120 hp force timing marks

With the throttle wide open and at cranking speed it should be sitting at 28?btdc if you have the prestolite magneto ignition.
If you have the thunderbolt cdi ignition then at cranking speed with throttle wide open it is 30?btdc.
This may be why its spitting back out of the carbs but if its still doing it after you correct the timing then you need to inspect the reed petals.
I made corrections about the proper timing sequence in my last response.
I blame the DROID.

 

[jerryjerry05]

Re: 1989 120 hp force timing marks

What are the compression #s?
The 21p SS is actually a 23 alum.
Might be a bit overpropped.
Pic of the flywheel and marks?
Plugs out while testing?
You gotta ground the plugs so they fire and don't destroy the packs.

 

[cheyenne52224]

Re: 1989 120 hp force timing marks

Compression is apprx 140 per cyl,I have run amzoil since new and was curious about wear.I removed the head and intake manifold last spring,everything looked as new so i milled the head .010,installed studs instead of head bolts.Installed a set of aftermarket 2 stage reeds,rebuilt and balanced the carbs.I thought that might get rid of the starting backfire out of the carbs,no luck.It does'nt do it all the time,more often when warm.Thats when i decided to adjust/check the timing. I thought it might be a little overproped also,unable to send pic of timing marks.To check timing I left the plugs in and clamped off the fuel line and ran it out of fuel,is that a problem?
I think i know what you mean about the props but could you elaborate why a 21 ss prop is like a 23 aluminum.Thanks

 

[bentle]

Re: 1989 120 hp force timing marks

If you are running between 24?-26? btdc then this needs to be corrected and may very well fix your prob. Needs to be static timed at 28? btdc or 30? btdc and depending on your ignition as I stated earlier.
I installed a 15look pitch on my 1994 120 force and wow what a difference it made on jumping out of the hole it made. Didn't loose any mph and never runs over 5500 rpms.