25ss engine (1973 vintage) need help w/ flywheel & timing

[ZUL8TR]

I am working on my Merc 25ss engine and need help assemblying the 3 piece flywheel. It was received in a box in 3 parts: (1)outer ring and magnets, (2)flex plate and (3) inner center piece that mounts on crank shaft that includes the recoil starter notched cup.

Since I do not have another assembled flywheel how do you determine the relative mounting position on the flex plate (2) of the outer ring (1) and the inner piece (3). The flex plate kit that I have describes that before dissassembly the relative position of (1) and (3) should be marked so reassemblly will preserve the relative position of these parts. That is great instruction if the flywheel was assembled when starting to work on!

Once assembled how do you adjust the max advance of this non breaker point magneto? I have a depth gage to set the piston to a BTDC position but after that point I am at a loss to know how to set the magneto to spark at that instant.

Any help is greally appreciated.

[CSH61CE]

timig

I am working on my Merc 25ss engine and need help assemblying the 3 piece flywheel. It was received in a box in 3 parts: (1)outer ring and magnets, (2)flex plate and (3) inner center piece that mounts on crank shaft that includes the recoil starter notched cup.

Since I do not have another assembled flywheel how do you determine the relative mounting position on the flex plate (2) of the outer ring (1) and the inner piece (3). The flex plate kit that I have describes that before dissassembly the relative position of (1) and (3) should be marked so reassemblly will preserve the relative position of these parts. That is great instruction if the flywheel was assembled when starting to work on!

Once assembled how do you adjust the max advance of this non breaker point magneto? I have a depth gage to set the piston to a BTDC position but after that point I am at a loss to know how to set the magneto to spark at that instant.

Any help is greally appreciated.

Hi zul8tr
First look on the flywheel,there should be 3 dots in a vertical line on the exterior side of the magnet rotor and approximately 2 inches to the right you should have 1 dot or one strait line, the line or dot should be the 0 top dead center and the 3 dots your timing degree. so place the no1 piston at top dead center and position the flywheel mark one dot or strait line in in the notch cup window on the recoil starter on your right side (put the mark in the center of the window). Then your flywheel will be synchronized.
You will then set the timing at the 3 dots line wide open with a test prop and a timing lite. If you have only one mark on the flywheel i will get you the timing degree next week my book is at the summer camp. or send me a picture of the marks on the flywheel and the serial number to my e-mail, there where many patterns on the flywheel in 70-75

Peter

[ZUL8TR]

The outer flywheel magnet ring (1) does not have the marks you note. All that I see are two 1/8" long vertical cuts 180 degrees apart along the cir***ference of the ring. I believe these are TDC locaters. The serial # of the 25ss engine is 3723765. The paper spec tag that came with the engine states 1973.

Since there is no timing mark other than the ones I note above is there another way to set the max advance without a Timing light without the engine running? I can set the piston to the correct position BTDC with an adjustable depth gauge.

Thanks

[3autility]

25ssh

It is possible you have a flywheel from a fishing motor, not a race motor. I think they are different. I have a fishing motor flywheel and it is vermuch differnt from the flywheel on my 25ssh motors.

[CSH61CE]

The outer flywheel magnet ring (1) does not have the marks you note. All that I see are two 1/8" long vertical cuts 180 degrees apart along the cir***ference of the ring. I believe these are TDC locaters. The serial # of the 25ss engine is 3723765. The paper spec tag that came with the engine states 1973.

Since there is no timing mark other than the ones I note above is there another way to set the max advance without a Timing light without the engine running? I can set the piston to the correct position BTDC with an adjustable depth gauge.

Thanks

I will get back to you
next week with the info.
and i doubt you can fix the max advance without the engine running and a timing light

Peter

[Jakeroub]

I had the same problem when I took my flywheel apart to have the flex plate shot peened. I forget exactly how I got it to go back together correctly, but I do remember that there are MANY possible combinations between the different positions that both the hub and outside can go, and the plate could be flipped upside down too.

I may have used another flywheel that was already assembled to help me.