25hp running rough until warmed up

[alabass]

Help me troubleshoot my problem please! I recently acquired a 1999 25hp 2-stroke, 2cyl., manual start. When I first start it up I have to let it idle probably 10 minutes or more before it will run correctly. If I try to run it out before then it cuts out, stumbles, spits and coughs and runs like junk. If I wait for it to warm up it runs like a top. What could be causing this? I was told it may be the thermo-switch assy. but this motor doesn't have one. I'm afraid in cooler weather it may never warm up enough to run properly. Help!!!

[jonp]

Hello,

I had a 25 for a while a bit older. Sounds like a fuel delivery thing. Make sure all you connections are good or replace them. Clean the small bowl at the fuel pump. You will need to unscrew the top bolt to dis-connect and clean the filter. Then run a cleaner in your fuel like Seafoam and see what happens. I had this happen on my 25 as well. I also opened the drain plugs on the carbs to drain them to be sure I had no water before I ran the seafoam. Run it with seafoam for a while an see what happens.

good luck

jon

[jonp]

If all this fails to help you may want to go for a fuel pump, not too expensive. Easy to replace. If this does not work then a carb overhaul...

good luck

jon

[alabass]

Guys, thanks for the suggestions. I pulled the carbs and they are pristine, look like brand new. I am however going to replace all the rubber gaskets and the fuel pump diaphragms to see if that makes a difference.

[Miles4721]

you may have low base pressure, caused by a leaking crankshaft seal ,most times the bottom crankshaft seal. I have seen this many times mostly on OMC products, but also yamaha. It sounds like a sneezing sound, coughs and engine kills. You can sometimes see black oily film under engine where the drive shaft goes into the crankshaft. Sometimes also you can see smoke come out the same area when it coughs and dies.

[PRdiver]

You can try empty the carbs when turning the engine off. When you flush the engine and it is ready to turn it off, disconect the fuel hose until the engine shuts down. Then install the hose again without pressing the prime bulb.

[alabass]

Update. I replaced all the rubber parts in the carbs including the fuel pump diaphragm and as stated in my previous post, the carbs are clean.

I took it for a test run and it started and idled fine but when trying to get up on plane it sputtered and cut out at about half throttle. I backed off and it seemed like one cyl. was not getting fuel. I pulled the choke for just an instant and the cyl. picked back up. At this point I could get it up on plane without it cutting out but when I slowed to idle one cyl. seemed to cut out again until I pulled the choke lever for just an instant. If I pulled it too long the motor would bog and die. I tweaked the linkage between the butterflies a little to synch the carbs which caused it to idle high so I adjusted the idle down. By this time the motor was good and warmed up and I had no more problems.

I guess I need to take it out cold one more time to see what happens. BTW I do always disconnect the fuel line when loading up and let it run until it dies and I always run Seafoam in my gas.

[jb123]

choked and improved = carbs....looks can be deceiving.
choke each throat with your finger while running to find the clogged carb.