40 hp Mariner

[bmotor]

Starts great runs great, but when put in neutral it stalls out and then won't start at all

 

[galamb]

A number of things can cause a stall in neutral. You are going to have to narrow it down.

Does it stop abruptly when you go to idle or does it kinda wind down and quit?

If it's the latter (which is common with a fuel/air issue) -

First thing I would do is remove the hood and take a good look at the powerhead. If it's really oily (you get a black goopy mess if you run your finger over the block) that could indicate a bad crank seal. A secondary indicator could be gas dripping from the lower cowl (you get rainbows in the water when it stalls out).

If you can rule out the seals you can start with the easy stuff first. Fresh gas and new spark plugs are the easiest and cheapest. Check the fuel filter for "crud" and your gas tank for water. Check the fuel line/primer bulb for leaks. If all that seems ok, it's time to clean the carb and inspect the fuel pump (clogged idle jets or a small perforation in the fuel pump diaphram can cause a stall at idle). Alternately, a stuck float valve could be flooding out the motor, killing it at idle and making a subsequent start very difficult.

Also, try and get it to run with the hood off. Look for gas spitting back through the carb throat - that could indicate broken or chipped reeds.