help identify TDC on flywheel's power of tower...

[tigerlegend2000]

i'm trying to do timing on my 85 mercury inline 6 and could not figure out where is 6 degree ATDC.... The mark is from left to right 464 then 16 white dots then number 21 and last are the numbers 9,6,3,0,5,10,15 (see pics. sorry took from the iphone, it's not that clear) i'd read a lot about link and sync in this forum but i will follow the sticker infront of the mounting plate. it said: M115 timing pickup 6 degree ATDC, Max spark 21 BTDC at cranking speed of 400 RPM which is 18 BTDC at 5500 RPM. Can anyone tell me where is my 6 degree ATDC is? i figure 21 degree BTDC should be at number 21 on the flywheel right? any thoughts? thank you very much....

 

[BoobieBouncer]

Re: help identify TDC on flywheel's power of tower...

I'm not a mechanic, but this is my guess for 6 degree ATDC:

 

[walleye1968]

Re: help identify TDC on flywheel's power of tower...

thatwoodbe my guess to
looks like each mark=1

 

[tigerlegend2000]

Re: help identify TDC on flywheel's power of tower...

Still unclear for me ... My manual said set it at .464 is the tdc. After tdc is 21 degree then the whole bunch of number to the right.. I though 6 degree should be the 6th white dot right after .464 tdc. Anyone has second though? Thanks

 

[Ware5150]

Re: help identify TDC on flywheel's power of tower...

I am learning all about my 85' 115 because of engine trouble. From what I have experienced the .464 mark is used to find the TDC when using a dial indicator. This is not actual TDC. The acutal TDC should be 0 on your indicators. Therefore anything to the left of 0 is BTDC and anything to the right of 0 should be ATDC.

I have the same issue on where to set mine. The manual says BTDC and the sticker says ATDC. But, I hope this clears up your question on the marks.

 

[tigerlegend2000]

Re: help identify TDC on flywheel's power of tower...

Ware5150
So what your suggestion? The 6th white dot after .464 tdc or the number that lineup as boobiebouncer pointout. Thanks

 

[Ware5150]

Re: help identify TDC on flywheel's power of tower...

I would time it at the number six to the right of 0 as shown in red.

 

[tigerlegend2000]

Re: help identify TDC on flywheel's power of tower...

i spent the whole day try to figure out tdc, 464, 6 atdc and 21 btdc.... i noticed that if the TDC is right at 464 mark on the flywheel, 6 degree ATDC is only at the 6th white dot after the 464 mark for primary pick up, if i played with it it could go only from 464 mark to the 9th white dot. For max spark advance, with the timing light, it move to the left of 464 mark, nowhere near the 21 mark that on the right of 464.... what i did at the end of the day was remove 8 nuts on top of flywheel, move the flywheel clockwise 1 slot over so tdc (instead at 464) now at number 0. For the primary pick up i could adjust to 6 ATDC as boobiebounce pointed out and supprisingly when i did max advance, timinglight show me axactly i'm at 21 degree BTDC (TDC is now at 0 instead of 464 mark)...

What do you guys think? am i in the right path?

the only thing is i have to do tomorrow is adjust primary pick up or air fuel mixture screw because it's only stay at 800rpm, won't let me go lower than that... i have 1 and 3/4 turn out as previous owner did that... anyone got any trick to go lower than that? thanks again

 

[Ware5150]

Re: help identify TDC on flywheel's power of tower...

Wow, that's a new one on me. Sounds like it is set where it needs to be though.

Are you getting 800rpm in the lake or with muffs. It will idle higher with muffs because there is no back pressure from the lake. 800rpm at idle is good. When you are setting it up you want it to idle around 600 rpm while idling in forward in gear. So when you come out of gear it will rise to around 800.

This is what I have read and should be correct. Hope it helps.

 

[Ware5150]

Re: help identify TDC on flywheel's power of tower...

Here is a link to proper Link & Sync procedures. This should help you finalize your setup.

http://forums.iboats.com/showthread.php?t=168855

 

[Smig]

Re: help identify TDC on flywheel's power of tower...

Here is a link to proper Link & Sync procedures. This should help you finalize your setup.

http://forums.iboats.com/showthread.php?t=168855

This is the thread that the FAQ came from:

http://forums.iboats.com/showthread.php?t=128495

The whole thing is great, but if you go way down past the 60th post, there is a discussion about finding TDC.

I had a similar problem as you and found that the previous owner had put the flywheel in the wrong position. This thread helped me figure out how to fix it.

Shaun

 

[BoobieBouncer]

Re: help identify TDC on flywheel's power of tower...

Are you using a Dial Indicator to find TDC?

The decal on the flywheel doesn't mean anything if TDC isn't correct...

I wouldn't run the motor with the change you have made if you aren't 100% sure that you did the right thing.

You will destroy your motor if you are wrong.

A boat mechanic charged me $85 to do the link and sync.

A mercury dial indicator costs $150.

 

[hkeiner]

Re: help identify TDC on flywheel's power of tower...

Here is another pic explaining how to set the timing pointer. This pic is from my Mercury 150hp V6 manual. The method described below is the same as that shown in the previous post, indicating that the procedure in the probably same for most of the higher horsepower Mercs. Also, you can get probably find a dial indicator online for under $20 that will do the job.