'69 18Hp Fastwin starts then dies!

bodiesel

Cadet
Joined
Aug 8, 2008
Messages
8
The motor starts well and seems to run strong at idle, but dies within 30 seconds. I checked the fuel pump and it seems to be working well. The gas tank and line aren't leaking. Is this a carb issue? What's my next move? Thanks.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: '69 18Hp Fastwin starts then dies!

Probably a dirty or gummed carburetor, but before you go tearing into it, first check the compression and spark. Spark should jump a 1/4" gap in free air.

Many a carb has been "rebuilt" and didn't fix the problem because the problem was somewhere else.
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: '69 18Hp Fastwin starts then dies!

when it dies, will it start right back up? check your spark as soon as it dies. if no spark it's electrical heating up. if you have spark, i would do a complete carb cleaning, and rebuild kit. also try this before rebuilding carbs.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

F_R & I typing at same time.
 

56 rude

Banned
Joined
Aug 8, 2008
Messages
198
Re: '69 18Hp Fastwin starts then dies!

Here,s someting to check also and trust me it happens ,it has happened to me with 3 motors so far that ive bought and tested or redone!MAKE SURE THE WATER PUMP IS WORKING!Many a hour has been spent looking for problems about poorly running outboards just to be that the impeller is pooched and the motor is overheating and shutting down!
 
Top