Relief hole in underwater exhaust pipe?

[GA_Boater]

At this point I'm wondering if these engines can run well at all with underwater exhaust.

Quite a difference between cutting blades of grass and spinning props in water. I'm guessing the torque and horsepower curves of a B&S outboard are much different than the same appearing and horsepower B&S mower motor.

Even B&S outboards are not underwater exhaust.

 

[jimmbo]

They very well might have different camshaft specs. Same goes for a marine engines cam spec vs. Car/Truck cam spec

 

[bikerider]

Quite a difference between cutting blades of grass and spinning props in water. I'm guessing the torque and horsepower curves of a B&S outboard are much different than the same appearing and horsepower B&S mower motor.

Even B&S outboards are not underwater exhaust.

My thoughts exactly. Since this is a custom application I am going to have to experiment until I find what works. It's been that way since I started the project, and I'm fine with that. If it really bothered me I would have bought an actual outboard.

 

[bikerider]

It would not be quiet. That is why exhaust is discharged under water

That's ok. With a Frankenstein motor like mine I'm just going to have to adjust to what works best.

 

[GA_Boater]

If it really bothered me I would have bought an actual outboard.

Where's the fun in that?

Maybe as a backup, an outboard some day?

 

[wrench 3]

Have you contemplated a chrome exhaust stack and slap a Kenworth emblem on it.

 

[bikerider]

Where's the fun in that?

Maybe as a backup, an outboard some day?

Exactly . That can always happen in the future. I have had a lot of fun putting it together and whatever use I get out of it is a bonus.

 

[bikerider]

Have you contemplated a chrome exhaust stack and slap a Kenworth emblem on it.

That way I can have bling and a sweet exhaust note haha :lol:

 

[jimmbo]

That way I can have bling and a sweet exhaust note haha :lol:

Some nut on shore will think you have 'Captains Call'(the very annoying option allowing a boater to bypass the underwater exhaust on an I/O, and dump it out the sides or transom sans mufflers) on your boat.

 

[wrench 3]

Some nut on shore will think you have 'Captains Call'(the very annoying option allowing a boater to bypass the underwater exhaust on an I/O, and dump it out the sides or transom sans mufflers) on your boat.

I rebuilt an engine in a 27' Century with two 350 Magnums and above water exhaust. He got me to repair the engine alarms while I was at it. It didn't do any good. You couldn't hear the audible alarms over the exhaust noise.
I told him that I could put a strobe light on the instrument panel for him but he never did that.