Hard Starting and Poor Running 1979 Mercury 50 HP

[NiKE Head]

Hi Guys!
Trying to get my boat started for the summer (a little late, I know), but I'm having issues getting it started. Two years ago my boat was running pretty poorly on the water. So I took the carbs off and sure enough they were extremely dirty. Once cleaned and put back on the boat pulled great! So great that I spent a little too much time on the water and ran out of gas. After getting back to the dock I packed the boat up and didn't get a chance to use it again that summer. The following summer (last summer) I was ready to go, filled up the tank and put the boat on the water and fired it up. Only this time the boat had no pull. At full throttle the boat was barely moving. So I packed the boat up for the summer again. Now trying the boat again I cleaned the carbs out thinking it was sucking up crap from the bottom of the tank but the carbs looked just as clean as they did when I cleaned them last year. Put the boat back together and still no luck starting. She starts with carb cleaner sprayed in her, but then runs rough and won't idle. The primer bulb gets stiff but then soft and I can hear air after a few seconds of not pumping.

Engine: 1978.5 Mercury 50HP 2-cycle 4 cylinder

Things I've done:
Took out carbs and cleaned jets
Replaced gas tank fuel line and primer bulb
Replaced fuel line and connector T in engine
Checked compression (120 psi across the board)
Checked for spark (new plugs and all 4 coils sparking with all 4 plugs)

Things I have yet to try:
Rebuild carbs again with new gaskets on the fuel inlet side (fuel pump?)
Sync carbs

Not to sure whats left to try but I am assuming its a fuel delivery issue now, maybe no pressure in the "pump"

Is there a setting for float height?

 

[Mercurylips]

I can only help to a certain level as I have been thru the wars with that same motor. I would recommend rebuilding and cleaning the carbs and fuel pumps again. (There are two of them, one on each carb but I think you know that). I strongly recommend a good manual to aid with the steps unless you are mechanically inclined to genius level. I took my tanks apart and cleaned them and got a new hose and bulb. Made sure that all the interior fuel lines were replaced and gaskets didn't leak. My wiring was brittle so it was replaced and the Stator was bad. Took two years to get it running like it should. Take the time on the carbs to blow out each and every crack, crevice and orifice. As for the floats, check to see how they are set. Turn the carb upside down and look for level. 1/4 inch should be height adjusted after new needle valves with springs not compressed. You have a great motor if you work out all the kinks of old age.

 

[CharlieB]

Hi Guys!
The primer bulb gets stiff but then soft and I can hear air after a few seconds of not pumping.

I am curious what is this 'air' that you are hearing?

Outboards need lots of fuel at WOT. A leaky fuel hose/fitting will allow air to be sucked into the hose, the carbs cannot stay FULL, the fuel level gets low, mixtures go lean, pistons MELT.

Follow my drift?

Double check all hoses and fittings, make sure clamps are tight and sealed.