96 Yamaha 9.9 4 str quits

[svsunbeam]

Our dingy motor is a 1996 Yamaha MSHU 9.9 4 cycle which has not been used for several years as we have been shore bound. In order to get it back in service I changed the water pump, Cleaned and put new guts in the carburetor, installed a new fuel pump, hoses and filters, new fuel lines, fuel tank and gas. With an electric drill and socket on the flywheel nut it will start up and run quite nicely but after a couple of minutes it will start to sputter and die. Fuel pressure seems good, but can't get the silly thing to stay running.... It seems to be over rich as when it dies it acts like it is flooded and won't restart unless you let it sit or give it a little shot of quick start. anyone got any ideas????
Thomas ... svsunbeam

[boats.net]

Must still have plugged passages in carb.

[svsunbeam]

svsunbeam

I soaked it for 2 days in spray can choke and carb cleaner ... is there a product you could recommend that works better?

[boats.net]

You need get some Yamaha Combustion Chamber cleaner or Mercury Power Tune to soak it with and use compressed air to check passage are open.

[svsunbeam]

svsunbeam

Thanks for the info Super Moderator, I'll give it a shot!

[wrightpwx]

Clean every passage

I have an 1985 F9.9. I had a problem with the engine due to carb. problems. Finally got if fixed when I blew out every single passage (front and back) with carb cleaner. Just soaking it won't work if there is dirt in the passages.

[svsunbeam]

96 yamaha 9.9 4 str quits

I did what you advised Supermoderator and got 2 cans of the Yamaha combustion chamber cleaner, emptied 1 and half of the other into a container and soaked the carb for about 5 hours then blew out everything I thought was a passage with compressed air a couple of times and reassembled all. I let it run for about half an hour in the barrel and then shot some of the combustion chamber cleaner into the air intake as per the directions on the can and changed the plugs. The motor now starts with the recoil starter but something is still not right.

Problem #1.... It starts up with 1 pull and runs at a perfect idle for about 45 seconds, then will gradually increase in speed to a rather fast idle (1min after start) and run at that fast idle till the thermostat opens (about 2 1/2 mins. after start. Then it will slow back down to a very slow idle and want to stall if I don't wiggle the throttle a bit. But if I do wiggle the throttle a bit it will run normally.


Problem #2... The engine now seems to have full power, but when running it in a barrel it will die after running it at full power for a couple of minutes. After it stalls it will start right back up.

It has now logged about a couple of hours run time it seems to be running better the longer it has been run..

Any ideas as to what is causing these problems??? Thank you for all your help Guys!! Your Ideas are a lifesaver!!!