Honda BF15 Exhaust Leak

"Inherited a 1990's 15 hp

"Inherited a 1990's 15 hp Honda outboard and 14' boat with instructions to take the kids fishing. Fist time out motor started immediately ran great unfortunately with in 5 minutes or so I noticed no tell tale water spray. Shut motor down, rowed back. Motor very hot. Installed new water impeller, sprays great. My problem is that motor purres like a kitten when hooked up to garden hose but will not run well when motor is in water unless cowling is removed. Back home ran motor with shaft in garbage can full of water same problem, runs great without cowling, hardly at all with cowling. Noticed that when ran with shaft submerged water appears in bottom of engine case and runs out drain hole, but exhaust gas is bubbling in this water. This does not happen when using garden hose attachement for cooling water. I assume that exhaust leak is fowling the air under cowling causing motor to run poorly. My question how difficult is it to fix? I cannot see the leak but it appears to be near where the exhaust exits the motor case heading down the shaft. Do I need to attack from the bottom or top? Is there a manifold and and exhaust tube? Is this a job for the shop? Also does anyone know what the initial mixture screw setting on the carb should be? Any help would be appreciated, the fish are in the river!"

"i had same problem with 8hp h

"i had same problem with 8hp honda, you are correct
exhaust is starving the air intake.
problem with mine was the exhaust tube was cracked
and had to be replaced.
I had to remove the head in order to get at the bolts to take off the cracked tube.
not an easy job, but if you have the tools ???"

"Stripped the Motor down last

"Stripped the Motor down last night. Started from the bottom, removed the propeller head and shaft extension. Found that there is a rubber like seal around the exhaust outlet on the bottom of the motor housing that I assume is to prevent water and exhaust gases from backing up into the motor housing after being discharged into the vertical shaft extension. The seal was melted and burnt from the overheating of the engine when the water pump had failed previously. Unfourtunately there is also a seal on the inside of the motor housing that required the complete removal of the engine in one piece to gain access. The 5 or so bolts that attach the motor to the housing are found on the bottom of the motor housing after the vertical shaft extension is removed. This seal was also melted and burnt. I am hoping that the replacement of these two seals will cure the problem of exhaust gas entering the motor housing and starving the engine of air. I could not see any cracks or other issues with the exhaust manifold/tube that is mounted to the motor. I am off to find the parts."

Finally had a chance to get th

Finally had a chance to get the boat out on the river and test drive my repairs. Everything works great. The replacement of the lower exhaust seal and the grommet on the inside of the housing was easier than I had feared it would be. Most of the replacement time was spent disconnecting and reconnecting the wiring and linkages so that I could get the motor out and back into the housing. All of the wires are color coded but it takes awhile to get them all tucked neatly back in place. The repair parts cost me a little over $50. The dealer gave me the correct setting for the carb air mixture screw. Tighten all the way in then back out 1 & 5/8 turns.