stalling when in water 50hp 1996

[espo]

on rack with muffs on it idles fine when put in water stalls every time.
have to keep it above 2500 rpm. put back on rack with muffs idles fine again.
????????? HELP

 

[jtexas]

Re: stalling when in water 50hp 1996

this is a common phenomenon. When the lower unit is submerged, there is backpressure on the underwater exhaust. On the muffs, the engine is completely unloaded, it'll idle on one cylinder. You can't really judge how well it's running till you put it in the water.

Been like this since you got it, or it was running fine up till now?
What recent maintenance has been done to this motor?
Any other symptoms? Cold start, warm start ok?
Fuel line holding pressure? Tank vent open and clear?
Premix or VRO?

Back to basics...compression test, then a spark test. Use an inline spark tester, gap set to 7/16", clipped to the engine block. Attach the plug leads (one at a time) and look for a good strong spark while cranking. Do this with both plugs removed and ground the floating lead while you test the other one.

report your results.

welcome to iboats.

 

[bkwapisz]

Re: stalling when in water 50hp 1996

this is a common phenomenon. When the lower unit is submerged, there is backpressure on the underwater exhaust. On the muffs, the engine is completely unloaded, it'll idle on one cylinder. You can't really judge how well it's running till you put it in the water.

Wow. Well this explains why I had my motor low-idling like a swiss watch on muffs and it's crappy on the water... Time for another tweak...

 

[espo]

Re: stalling when in water 50hp 1996

gap 7/16 ? book said .030
oil injected
use to run fine
Still starts right up with a little choking and gas.
Did notice gas bulb a litte soft after sitting a day.
will start doing the things you said tomorrow, will let you know
Thanks
Joe

 

[jtexas]

Re: stalling when in water 50hp 1996

Set your spark plug gap at .030

But for a spark test (not a *spark plug* test), use an "Inline Spark Tester" (couple bucks at Autozone), with the gap set at 7/16. This is to test whether the ignition system is generating enough electricity to fire the spark plug in the heat and compression of the combustion chamber -- a half-inch in the open air makes for a good visual test.

If it's holding pressure all day, should be good enough.

 

[espo]

Re: stalling when in water 50hp 1996

good spark
compression 140 both cyl.
found cracked hose from air box to motor, fixed
in water now idles at 1200 than all by its self goes up to 2000 rpm
on rack runs at 2000 rpm from get go