[hawkman222]

I have a 1970 40HP evinrude model 40073A. A few weeks ago I took it out and it ran fine for the first 15 - 20 minutes, then it stalled out at WOT and I had to limp it back to the dock. I replaced the coils, cleaned the carb, replaced and adjusted the carb float yesterday. I took it out this morning and it ran like a champ, I thought I had the problem solved. Then about 1/2 hour into the run, it bogged out. I was at WOT and it just died. It started right back up, but as I tried to get it throttle, it wanted to sputter and die. so I limped back to the dock again with it. Here's what I know.
1. New carb kit (less float ) this spring.
2. New coils new float yesterday.
3. New points this spring.
4. There appears to be oil leaking out of one of the crankcase cover to block bolt holes just in front of the by-pass covers.
5 There also seems to be a lot of fresh oil on the bottom of the powerhead where it bolts to the exhaust housing.
6. I pulled the head and found that the lower cylinder piston top looks whiter and dryer than the top of the upper piston.

I'm thinking maybe a primary compression issue. Any thoughts?

[F_R]

I sort of doubt it.

Can you keep it running by squeezing the primer bulb? If so, that would indicate a bad fuel pump or air leak in the hoses somewhere. I'm suspecting fuel pump. That would also make the cylinder to which it is mounted run richer.

The other culprit could be the high speed jet orfice plug in the bottom of the carb bowl. Maybe crud floating around in it, causing the intermittant loss of power.

You aren't cutting out on one cylinder are you?

[hawkman222]

The way it ran after it stalled out seemed like only one cylinder was operating. The fuel pump is the one thing I haven't checked. I squeazed the bulb right after it died and it felt pretty firm. I didn't try sqeazing it while running. Yesterday I removed the high speed orifice and it was ok . How would I test the fuel pump?