Drilling out the exhaust.

Mercury115SS

Recruit
Joined
Feb 20, 2011
Messages
2
I have a Mercury 115. How do I drill out the exhaust so it sounds louder while in the water and give the motor more power. I saw a guy on the river one day who said he had done this before. Just wondering if it is possible and how to do it.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,464
Re: Drilling out the exhaust.

Ayuh,... It Ain't that Simple, 'n this Ain't a Prop question....

I'll ge this moved to the Mercury Outboard forum...
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
Re: Drilling out the exhaust.

Sounds like he was a pulling on your leg!!!The only way to get more power from drilling out anything is reboring the cylinders.Then u will only get maybe 5 hp more.
Usually getting more power means a bigger motor.J
 

Droll

Chief Petty Officer
Joined
Jul 30, 2003
Messages
514
Re: Drilling out the exhaust.

The only way drilling holes can provide more "power" are this one...
Prop%20Ventilation%20Holes%20Info.jpeg


This mod can give you a bit more power out of the hole IF you got the right boat/engine combo..

Drilling the exhaust other ways will in most cases just make more noise and weaken your driveshaft housing ( leg ).


Arne Kjetil
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Drilling out the exhaust.

1st problem, noise ordinances, get loud, get noticed, get ticketed.

2nd problem, IF, (notice that's big), IF, you did manage to get more air to flow, that would change the fuel/air mixture and melt pistons. It ain't so easy to jet an outboard, but it can be done, just be ready to rebuilt it if/when you smoke it til you get it right.

The extreme low pressure area created behind the prop hub by forward movement in the water works VERY well in scavaging/pulling the exhaust out of the motor.

It is VERY difficult to improve on Merc engineering, they have been doing this for quite a while.
 
Last edited:

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: Drilling out the exhaust.

More noise does not make more power. It just makes for more annoyed folks on the water.
 
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