'78 Merc 898 5.0 hard start when warm

[hef05]

I've read all the forms I can I can find about warm hard starts. Boat starts strong when cold. I rebuilt the carb this spring but still having to do WOT when the boat is warm to get a quick but loud high rpm start! Is there any adjustments to make to the carb float or anything else that will help with this? I do believe it's a flooding issue. I adjusted the electric choke a little more lean but still starting hard when warm/flooded. Any help is appreciated!!! Thanks!

 

[Scott Danforth]

Leaking welsh plugs would be my first thought

 

[kenny nunez]

Also another thing to try is with a volt meter check the voltage at the + side of the coil when cranking. You should have at least 12 volts in cranking mode then depending whether if you have a points ignition it should drop to 8 volts after starting or If you have the electronic ignition then it will be 12 volts running.
If you have very low voltage at the coil when cranking then the “by pass” circuit in the starter solenoid is not making contact. You will have to remove the starter to replace it.

 

[hef05]

Leaking Welsh plugs? As in the freeze plugs in the engine block? Can you go into more detail as to how to get

 

[harringtondav]

Leaking Welsh plugs? As in the freeze plugs in the engine block? Can you go into more detail as to how to get

I believe SD was talking about the plugs in your carb. They seal areas where cross drilled passages were machined.
In my experience WOT hot starts fix flooding or too rich idle mixtures. Also a too high float setting can cause flooding/over rich mixture.

Never pump a hot engine. Slowly (to minimize accel pump enrichment) open the throttle a moderate amount and see if this helps. Also check your choke plate when your engine is hot. It should be full open. If not, adjust it.

 

[Scott Danforth]

Dave is correct. Q-jets have an issue with the welsh plugs leaking fuel down the intake