Shade Tree Mech Help On Yamaha F9.9 Outboard.

[99yam40]

Yes the manual should give you the info needed.
Would have been nice to have made sure the timing was out or still good before you took things apart.
Some thing caused this to happen.
A motor that old probably should have had the belt replaced long ago, may have jumped because of stretched belt. Does not have to move far to cause this problem, just one or two teeth. Make sure you replace and get it all in proper time.

[mphelle8vld]

The factory service manual is always a good idea.

Something malfunctioned while it was running that allowed the pistons to contact the valve heads, possibly a stretched drive belt that jumped time or a sheared flywheel key, while you wait for parts, find your flywheel timing marks and place it on top dead center and then look at the top piston to verify it's at TDC. That will eliminate the flywheel key as a suspect. I would replace the belt no matter what.

Just saw 99yam40's post after I posted, I shall defer

[roosterlips]

Parts have arrived

I have received my new parts from boats.net.
Installed the two new exhaust valves
Reinstalled the cylinder head.
Exhaust and Intake valves open and close when I manually turn the drive gear...will make valve clearance adjustments in near future.

Was going to install the new timing belt but the service manual indicates that I need two special tools to remove the flywheel magneto.
Flywheel magneto holder PN#YB-6139 and a Flywheel magneto puller PN#YB-6117.
I searched on the net for these parts with no luck. I called a Yamaha dealer and each tool is over $200.00 bucks...Can't see it.
I inspected the existing belt and it looks ok to me...the motor has not had a lot of run hours at all and probably won't get many more. It may get used once or twice a year.

Anyway I aligned the marks on the cylinder head driven gear and cylinder head as instructed in the service manual.
The manual instructed me to align the marks on the drive gear and cylinder body, however I can't see the mark on the drive gear without removing the flywheel...without the special tools I don't think I can get it off.

After manipulating the drive gear/flywheel position and reinstalling the timing belt the pistons now complete their full stroke without contacting the intake and exhaust valves.
Obviously I don't have a clue...Can I continue on from this point and attempt to adjust the timing with a timing light or am I looking for trouble??

[roosterlips]

After thinking about it I think I will attempt to make these tools myself so I can get the timing belt replaced.

[boats.net]

Best to get the tools and make sure timing is right.

[roosterlips]

I have now replaced the timing belt and buttoned everything up.
Motor fired up after about 5 pulls...hurray!
Motor seemed to idle with no issues.
After letting it warm up I revved it up and it seemed to be fine, however
after it ran for a while it started to act up when I revved it up. Coughing, sputtering and wanting to die.
I have not put a timing light on it as of yet.
Could a timing issue cause this?

[roosterlips]

Outboard starts but dies after warming up

I started the motor up this morning and it runs fine while cold, it revs up and sounds good, however it dies after warming up.
I pulled the lower plug and it appeared to be slightly damp.
Could my problem be that once the thermostat opens up I'm getting water into the chambers causing it to die?
I pulled the valve cover and increased the head bolts torque from the sevice manual recommended 22ft.lb to 30 ft.lb.
Restarted the motor and once again it did fine while cold but dies after warming up. I did not put any sealent around the head gasket when I installed it.
The service manual did not call for sealent.
I had cleaned the head surfaces very well before installing the new head gasket.

Cooling Water Flow.pdf

[99yam40]

hard to say from here, but may have cracked the head.