4 Stroke 9.9 Yamaha Problems

[oldiron52]

I bought a 1987 Yamaha saltwater 9.9 electric start 20 inch 4 stroke in pretty good all original condition for a hundred bucks. I went through the carb, which was a little nasty, but now seems to be all good and clean. 2 problems: (1) to start this motor, I must put thumb over the air intake of carb. She dies when try to get to idle under 1800 RPM (idle jet adjustment seems to have no effect). The plunger at the top of the carb is automatically coming all the way down when it is running (should this happen?). Gas is dripping out of the throat of the carb. The float was working as designed to stop and start fuel flow. Above 1800 RPM she does stay running and pumps water well but runs rough. (2) Lower unit does function fine, however she is taking on a little water. Where should I start with this problem? Is it possibly a simple to replace seal at the prop shaft end? I?m new to Yamaha?s; I know these type leaks can be several things but was just wondering if a seasoned person could tell me what?s most likely. In advance, thanks for listening?Scott

 

[Eshaw150]

Re: 4 Stroke 9.9 Yamaha Problems

First off Yamaha Did not make a 4 stroke in 1987 and we need a model number to help veriefy the proplems and designs

 

[rodbolt]

Re: 4 Stroke 9.9 Yamaha Problems

the F9.9 was imported to the US in 1986 and has been here ever since.
the carb MUST be redone with NEW needle valve and gaskets.
the automatic enrichment system is vacum operated using a bimetallice thermal valve and must be plumbed and tested in accordance with your service manual.
I suggest the Yamaha manual over all others especially for the carb and gear case work.
I can tell you from your description that the carb is still nasty.
I would start with a leakdown test and a spark test.

 

[oldiron52]

Re: 4 Stroke 9.9 Yamaha Problems

My apologies, I should have provided model FT9.9EXH, code 6G8, S/N 782010 salt water edition (white in color) right up front for this motor. Obviously the seller (2nd owner) did not know the year either. However, when I cross referenced this motor on iboats it came up with 1991?1994. There is no letter in the S/N that would lead me to the exact year. Again, thank you for your time?Scott

 

[oldiron52]

Re: 4 Stroke 9.9 Yamaha Problems

rodbolt ? Thank you!! I followed all your advice and cleaned the carb in an acid bath this time, ordered a few new parts and the motor runs and idles as if she were brand new. Now onto the lower unit. Again, thank you!!

Eshaw150 ? Please do not reply to any more of my posts due to your lack of knowledge on outboards. You made yourself look like an idiot when you bluntly posted that Yamaha did not make a 4 stroke in 1987

 

[oldiron52]

Re: 4 Stroke 9.9 Yamaha Problems

Resealed and painted the lower unit which made this 1987 Yamaha 4 stroke run like new again. I just sold her for $800 which was a $600 profit. I just want to say thank you to all who helped make this possible. I had fun, and learned a lot from you with my first experience working on a 4 stroke.

 

[rodbolt]

Re: 4 Stroke 9.9 Yamaha Problems

good deal, but dont bust on ershaw150, they did not import many and you had not provided a model number at that time.
the last alpha character H on your motor identifies the year of production.
ther were a few anomallys on the yamaha model codes for US market motors that can get confusing,especially with the older tiny motors.
the US market was about the only market that Yamaha tried to use year of production and that stopped with the 2006 production runs.
now everything is broken into seriel number groups,much better system.
kinda like a 4th alpha character D, is it 1990 or a 2005 model?
takes a year or two to figgure out how to deal with stuff without actually seeing it.
maybe one day ill learn to type and spell .

 

[Eshaw150]

Re: 4 Stroke 9.9 Yamaha Problems

good deal, but dont bust on ershaw150, they did not import many and you had not provided a model number at that time.
the last alpha character H on your motor identifies the year of production.
ther were a few anomallys on the yamaha model codes for US market motors that can get confusing,especially with the older tiny motors.
the US market was about the only market that Yamaha tried to use year of production and that stopped with the 2006 production runs.
now everything is broken into seriel number groups,much better system.
kinda like a 4th alpha character D, is it 1990 or a 2005 model?
takes a year or two to figgure out how to deal with stuff without actually seeing it.
maybe one day ill learn to type and spell .

Srry my bad i didnt no that I havent been into boats a long time and dont have as much knowledge as rod bolt. There aint no reason to get mad. If thats the way u want to be then thats fine. But ull lose alot of help that way good luck to u

 

[lakedipper]

oldiron52.

What service manual, if any, did you end up getting and where? I have the same engine FT9.9EXH serial no 781550 25 inch shaft high thrust which has been working fine for the most part until recently. I have not owned this very long and have to go through it this winter and tighten everything up as things are rattling loose.

My latest issue is fuel related and I'm afraid I'm missing parts on the carb. There are two small rubber hoses, one cut at an angle which is not attached to anything. Suspect that it is either a drain hose or that it in deed should be attached to something that is no longer there....

Take a look at my picture and any feedback is appreciated.

Outboard is hanging off a 25 ft sailboat on a Garelick/EEz-In 71090:01 Marine Aluminum Auxiliary Motor Bracket

which I absolutely love by the way. Not at all related, but I had a hard time finding good reviews on the bracket when I bought it.

 

[lakedipper]

Update. Been doing some looking and plan on cleaning my jets. Will post results and pictures.

 

[99yam40]

do not post on old dead threads

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