timing

[joe84]

1975 850 mercury; the guy that had the boat before i bought it pulled a the bolts out fly wheel do i go by marks on fly wheel or decal marks on flywheel and pointer is only for timing light use and distibutor pulley is for hand setting correct? if i have to move it to one of te three dots which one should i use for BTDC can any one point me in the right direction please

 

[oldman570]

Re: timing

The easy way to find the correct timming is to borrow a degree wheel from someone or pull the top plug and turn the motor over by hand untill you have the piston at the very top of the cylender. Then put the flywheel on the keyed crankshaft and see what timming marks line up with the pointer at TDC. Always turn the flywheel clockwise. With a flexable tape measure measure the outside of the flywheel then divide that number by 360 and that measurement will be for 1 deg.of timming, multyiplying 1deg. measurement by what you need for timming set will give you what you need. One of the marks on the flywheel is for setting the distrubeter when replacing the timming belt or working on the distrubetor, and the other is for setting the correct advance with a timming light. Usually the first mark should line up with the pointer and the second should lineup with the center of the crank and the center of the distrubeter shaft. A OMC manual is a very good investment when working with these motors.
Oldman570
Oldman570

 

[joe84]

Re: timing

The easy way to find the correct timming is to borrow a degree wheel from someone or pull the top plug and turn the motor over by hand untill you have the piston at the very top of the cylender. Then put the flywheel on the keyed crankshaft and see what timming marks line up with the pointer at TDC. Always turn the flywheel clockwise. With a flexable tape measure measure the outside of the flywheel then divide that number by 360 and that measurement will be for 1 deg.of timming, multyiplying 1deg. measurement by what you need for timming set will give you what you need. One of the marks on the flywheel is for setting the distrubeter when replacing the timming belt or working on the distrubetor, and the other is for setting the correct advance with a timming light. Usually the first mark should line up with the pointer and the second should lineup with the center of the crank and the center of the distrubeter shaft. A OMC manual is a very good investment when working with these motors.
Oldman570
Oldman570

can you tell me if the decal or 3 indentions in fly wheel are for distributor alignment?

 

[Chris1956]

Re: timing

Joe, First make sure the outer flywheel is installed correctly. Set the top piston to top dead center. The timing mark on the cowling should indicate nearly TDC on the timing decal. If it is off by 35*, you need to remove, rotate and reinstall the outer flywheel. Remove the 8 bolts and turn the outer flywheel until it lines up with the timing marks. Install the 8 bolts with some blue locktight.

Now to time it...Set the TDC on the decal on the flywheel to match the timing mark. Remove the distributor pully cover and see if the cast arrow is pointing at the one or three dots(whichever you have) on the timing decal. If not, remove timing belt and adjust pulley until it is.

 

[joe84]

Re: timing

thanks guys do you have any suggestions on bringing a boat back to life i bought a manual i just didnt see any thing if someone removed fly whee please share any knowledge you have im eager to learnl

 

[Chris1956]

Re: timing

Joe, That picture shows the inner flywheel only. Do you have the rest of it?

 

[joe84]

Re: timing

yeah i have the rest of it i got good spark and compression so now its time to tackle carbs any pointers

 

[Chris1956]

Re: timing

Sure, remove, disassemble and soak them in carb cleaner. Blow out all passages with compressed air or carb cleaner. Now reassemble with new gaskets, inlet needle and seat, and floats. Set idle mixture needle to 1-1/2 turns out from lightly seated. Now perform link and synch.