Re: 76 johnson need help
Typical, we've all been there. with the prop submerged, there's backpressure on the underwater exhaust. On the muffs it's completely unloaded, so it sounds great.
It's one of 3 things: compression, spark or fuel.
compression test -- compression should be about the same on all three, within 5 or 7% or so. Upwards of 100 PSI is good.
spark test -- not a *spark plug* test. spark should jump a 7/16" gap on an inline tester outside the cylinder.
Make sure you have fresh 87-octane gasoline mixed 50:1 with TCW3-certified oil. The primer bulb should get & stay firm when you pump it up. Tank vent must be open and clear.
Make sure the timer base moves smoothly without sticking. Make sure the chokes plates are all completely open execpt when the choke is engaged. Make sure the throttle butterflies are parallel.
If all this checks out, rebuild your carbs.
Here's a good how-to:
http://forums.iboats.com/showthread.php?t=244013
highly recommend the factory service manual, it'll more than pay for itself.
on the muffs, don't rev your engine any higher than needed to warm up a cold engine -- without a load, you risk thermal runaway, with potentially disastrous consequences.
welcome to iboats!
