mercury 9.9 runs 30 seconds then stalls

[Bluestream]

I have a 89 Merc 9.9 (not a Yamaha) that only starts when cold and runs for about 30 seconds and stalls. after that it will fire for 3-4 seconds and stalls each time. Plugs are wet when removed and fuel shows in water, so it is running rich.

Compression good at 105 PSI in both
New plugs installed, both getting good spark. (has aftermarket CDI box)
Carb (has carb from an 8HP) was taken apart and was clean. Fuel needle/seat held pressure for 10 min
Reeds appeared to be good and sealed tight
Float was good and main jet clean
Low speed jet at 11/4 turns out

At wits end, any other ideas? Its obviously getting too much fuel, but why?

 

[Sea Rider]

What happened to the factory delivered 9.9 carb ? That OB should have timing advance and carb synch set for a 9.9 carb not a 8 HP carb.

Happy Boating

 

[Bluestream]

What happened to the factory delivered 9.9 carb ? That OB should have timing advance and carb synch set for a 9.9 carb not a 8 HP carb.

Happy Boating

The previous owner switched the carb. Cant see the timing advance causeing to run rich. And what do you mean by "carb sync"?

 

[flyingscott]

Look at the primer assembly those like to leak and will cause it to flood especially the ball and spring. The ball can get compressed into the spring.. Get a full rebuild kit for it that has all the gaskets including fuel pump and primer. The timing advance on the 6/8/9.9 motors is the same.

 

[Bluestream]

Scott, that makes perfect sense. I took the carb off and took primer apart and there is no ball in there at all. I assume it should be on top of the spring (size of a ball point pen spring) that goes in the bottom when brass plug is removed. Unfortunately, 1395-9844A repair kit does not include the ball I would hate to have to buy the full kit at $124US just to get that ball.

Edit: I stand corrected it appears the ball may be included after all

 

[flyingscott]

When i lose them I replace them with a stainless ball bearing from the local bearing place.

 

[Bluestream]

When i lose them I replace them with a stainless ball bearing from the local bearing place.

I thought of that, I'm sure I have some small bearings around. Thanks again for the help

 

[flyingscott]

I thought of that, I'm sure I have some small bearings around. Thanks again for the help

http://www.ebay.com/itm/NIB-Mercury...ash=item462a06e27f:g:7xkAAOSw8vZXMf8Q&vxp=mtr check this out

 

[Bluestream]

Thanks...do you know if the ball sits directly on the spring, ot is there a small holder that the ball sits on?

 

[flyingscott]

Thanks...do you know if the ball sits directly on the spring, ot is there a small holder that the ball sits on?

When you assemble that assemble the diaphragm part last. Assemble the checkvalve assembly and install first. Yes the ball sits directly on the spring.

 

[Bluestream]

I took the check ball from my 9.9 Mariner and found it to be 1/8 inch. I went to a local bicycle repair shop and asked if they had any balls bearings, and they had lots, and gave me some fro free. Installed in the primer and the engine now runs great. Still need to do a full water test and find a 9,9 carb to fit it.

Thanks tp Flyingscott for the advice!