Briggs and stratton outboard

[dooger]

I have had a Briggs outboard for a year and I like it, very dependable. Has any of the other owners on this board thought about burying (plumb) the exhaust underwater when the warranty runs out? Will this work? What size pipe? I have a 3 1/2 hp Briggs outboard that is old, I may try on that one first,Doug.

 

[Drowned Rat]

Re: Briggs and stratton outboard

I wouldn't do that, dooger. 2 reasons. That motor is designed to run with a preset exhaust pressure. If you run the exhaust underwater, you increase the pressure and the motor will lose horsepower and you may blow a gasket or two. You have to get the exhaust out to get the fuel and air in. Have you ever noticed that most outboards have a idle exhaust relief that is above water? There is a reason for that. If you hard pipe your exhaust underwater, you won't have that relief port. 2nd bad thing that can happen is you will suck water back up the exhaust into the cylinder either when starting or stopping the motor. When the engine "kicks back", and it will, you create a negative pressure in the exhaust which will pull the water up. That's a great little motor you have there, just deal with the noise.

 

[dooger]

Re: Briggs and stratton outboard

Drowned Rat,<br /> Maybe I could put a T inline with a standard muffler just above the water line. This would give exhaust relief plus break the vacuum.<br />Just more thoughts, dooger.

 

[Drowned Rat]

Re: Briggs and stratton outboard

Ok, but what is the point, and why just above the waterline? If the gasses exit through the muffler you still have the noise, if they exit underwater you still have the excessive exhaust pressure. Also remember this is an air cooled motor. The last thing you need is a backup of HOT exhaust gasses to add heat to the motor. This is an important consideration with this motor at any RPM. Even extending the length of the piping leading to the muffler could have adverse affects it terms of heat retention. Just don't want to see you fry your motor.

 

[dooger]

Re: Briggs and stratton outboard

Maybe I'll leave well enough alone, dooger.