Mercury 40HP Issue

[hutch4113]

Asking this question on behalf of a friend. He has a 40HP Oil Injected Merc...not sure on the year, but would guess mid to late 90's model.

The Motor has been tuned up, and ran great the first day. Started and idled fine.

However that last couple of trips we have gone out, the following as started to happen:

1)Will start fine, but only idle for about 2 minutes before dying (unless the throttle is up.
2)Putting it into drive, and then pushing the throttle up causes it to stall out (unless you firewall it...and even then it is sometimes iffy).

Once either one of those happens, to restart the motor requires full throttle & choke.

We have checked the vent on the tank, which seems to be fine. The engine runs great from 1/4 to full throttle...no hickups, sputters or anything. All issues are at the low RPM range.

Gas is new (not last years).

Any thoughts would be greatly appreciated.

[JP]

When the motor was "tuned up" were the carbs and low speed jets cleaned? If these jets have any debris at all in them the engine will have a hard time idling. Also if there is residue in the carbs from old gas not being drained correctly while stored over the winter then that might be the issue with dirty carbs.

Try removing the gas line, pump the ball hard then re install it on the outboard. We have had some issues with vapor lock in older small diameter gas lines. keep your face away from the point of connection as gas under pressure might spry while connecting.

Check your gas/oil mix. If there is to much oil to gas ratio then the motor may stall out at low speeds.

let me knwo how it goes

JP

[Haybay Larry]

You should also look at the fuel filter on the engine. Also look over the primer bulb and connections. A small hole in the fuel line or loose clamp connection can cause a miriad of problems.
...Larry