Exhaust coming out under the power head

modesto · Feb 25, 2021

I bought a 1978 25hp johnson and the exhaust is coming out from under the powerhead and not out of the propeller area. Could the exhaust tube be clogged. I just rebuilt the carb. and started the engine which seems really tight when pulling the rope and then when it starts for about 10 seconds it bogs down and dies. Does anyone have any suggestions?

F_R · Feb 25, 2021

Exhaust tube clogged??? Nah.

oldboat1 · Feb 25, 2021

Make a stand for it, and test run it in a large trash can -- water a few inches above the pump. Better, just fill the can about half way up the leg of the motor. If the motor is mounted directly above the can (say on the side of the water barrel), exhaust will make it up to the carb and choke out the motor. Some folks set up a box fan to blow away exhaust when driveway testing.

modesto · Feb 26, 2021

I have it in a barrel when I tested it. The smoke is coming out of both sides of the engine underneath. Compression was 100 on both cylinders. No bubbles or exhaust seen coming out of the tail prop area. Could I have a crack in the block. Sorry I work mostly on cars and small engines but I am learning. Thank You