Chris Selwyn-Smith wrote:
Hi
I have just aquired a cheap Yamaha Outboard which I am in the process of
servicing.

Can any one tell me the appropriate points gap and timing degrees for my
8HP Yamaha, Model 8B, serial number 677S005141 I believe its 1977?

It would seem to be impossible to buy aSeloc or Clymer manual for a 1977
Yamaha, would a Mariner Manual for that period cover this model as I
understand Yamaha used to make some of the older Mariners ?

I would also appreciate any links for further information on this engine.

Thanks
Chris

Chris,

The earliest I can find in this place is for the 84 model so this might
be a total waste of your time, but being another Smith you'll appreciate
me trying to help anyway:-)

It seems by 84 anyway they no longer had "points" & other than the very
little motors neither did the other brands, so I'm wondering if your
engine has points??

(i) Check to see the timing pointer does actually point to TDC
particularly with older carryable engines, it might be bent, moved etc.
(a) Take the spark plug & break the porcelain centre out if it (you'll
be giving it a new plug anyway??), put a small nut & bolt through the
hole where the plugs' insides were so the tail of the bolt will hang
into the combustion chamber a little way & stop the piston getting to
TDC. Put in in the head finger tight with the piston down the bore.

(b) Carefully & slowly by hand turn the flywheel till the piston just
touches the bolt. Mark the flywheel (scribe? but a pencil is fine) where
the TDC pointer is pointing. Again carefully & slowly by hand now turn
the flywheel the other way so the piston goes down then will again
contact the bolt tail on the way up again. Mark the flywheel where the
TDC pointer is now pointing.

(c) With a tape now measure the distance between your two pencil marks
on the flywheel, The pointer in it's current position is pointing to TDC
exactly halfway between the two marks, which if everything is as
original will also be where the flywheel is marked TDC, if it isn't;
then you can bend or move the pointer so it will be.

(d) Repeat the process just to be sure the pointer does actually point
to TDC.

TAKE THE PLUG WITH THE BOLT IN IT OUT NOW, BEFORE YOU FORGET & TRY TO
TURN THE ENGINE OVER WITH IT STILL THE-)

(ii) The max advance for the 84 model is 35 deg BTDC the amount of spark
retard (ATDC) at idle is not adjustable & it reliant upon the max being
correctly set. To adjust;
(a) Disconnect the link rod which move the base of the magneto. With
the engine running (test tank but on the boat is half OK) Move (adjust)
the stop as appropriate till the max timing is right with the magneto
based turned against the stop, tighten the stop. Be careful & safe.

(iii) To adjust the sych, (engine off) turn the throttle to WOT & make
sure the throttle lever on the carb is just against it's stop, if not
adjust till it is (locknut on the tight cable?)

Leaving the throttle at WOT rotate the magneto base plate till it rests
against the max advance stop, then adjust the length of the link rod so
it will clip onto the carb linkage without changing the timing setup.

Turn the throttle to slow, & make sure the starter limiter is still
preventing start at more then slow. If not; adjust.

Apologies again for not having the 77 stuff but this might help if you
don't do better elsewhere

K