75 85hp mercury

[jvoldarski]

i am trying to set the max timing on my 850 and i have no idea how to do that because the timing strip is missing off the flywheel... is there anwhere i can buy one to put on or is there a way i can do it without it the flywheel has 3 little dots on it but thats it.

 

[194269]

Re: 75 85hp mercury

The only other way is to use depth mic. on #1 piston. You have to find TDC on #1 first and then back the piston down to the dimension that Mercury specifies, such as .235 BTDC (this is only an example, may not be the correct figure) and then mark the flywheel. Good luck

 

[merc850]

Re: 75 85hp mercury

Here's my flywheel and decal, a 1975 Merc 850, I have my max spark set at 24*

 

[jvoldarski]

Re: 75 85hp mercury

thanks for the info i dont have access to a depth mic but do you think a good set of calipers would be accurate enough or a dial indicator

 

[Chris1956]

Re: 75 85hp mercury

I would politely ask Merc850 to accurately measure (usuing a cloth tape measure) from the three dots to 5* BTDC and 21* BTDC and the .464" dot, and send the measurements to you. You can then transfer them to your flywheel with some white paint and time the motor.

 

[merc850]

Re: 75 85hp mercury

There is a steel tape measure in the photo and here are the values
TDC 1.25"
Throttle pickup 1.50"
Max distributor advance 3"(25*) -2 5/8" (21*)
Timing pointer 4-13/32"
I have mine running at 24* and seems fine, check TDC first to make sure the flywheel hasn't been tampered with.

 

[jvoldarski]

Re: 75 85hp mercury

Thanks for all the info now to just find the time to work on it