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2.5 Standard gear Mid-Sections Exhaust Question

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Old 03-26-2002, 12:42 PM
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Default 2.5 Standard gear Mid-Sections Exhaust Question

I know I know we have a tech section for this too. I will post this there as well. In the mean time, I have twin 2.5's with standard mid-sections, not the offshore housings. I have heard that you can drill out the exhaust at the point where the mid-section meets the lower unit to improve exhaust flow. Stock exhaust exits over the prop as well as through exhaust holes. Can anyone shed some light on this or point me in the right direction as to where to get more detailed info?

Here are my questions:

1. Does this improve performance or help the engine run any smoother?
2. Where EXACTLY do you drill and is there a template and where do I locate one?
3. What size hole and how many do you drill?

Thanks in advance.

Shane
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Old 03-26-2002, 12:53 PM
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Shane, I drilled my old mids just above the lower units, there is a lip where the end of the exhaust basket narrows and goes into the lower, you need to pull the powerheads, remove the inner basket if you have one and drill about 5 to 6 holes on each side, do not drill holes anywhere on the back of the mid section, as far as performance, it sounds good and does let the motor breathe alittle better but I didn't see any performance gain. Are you coming next week or what!!!!!!!!!!!!!!

Give me your # I'll call you if its ok!

As far as the size I think I used a 3/8 inch drill bit

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Old 03-26-2002, 12:55 PM
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hey shane packinair just had his mids shortened by eagle one down in fla. they drilled out his lowers while they were at it. we'll try and get some pics and measurements to you . you might want to give them a call as they filled us in on all the tech stuff about diong this.
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Old 03-26-2002, 01:51 PM
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Thanks guys! I really appreciate your replies! It seems that it probably is not worth it especially since they are cracking down on noise on my home lake. Just thought I would ask. Skatermike24, I'll PM you my info!

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Old 03-26-2002, 01:54 PM
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Skatermike24,

No I am not coming down as my friend is not racing at the Lake Toho race. I see I cannot PM you as you are not set up for them. I will e-mail you my numbers from home tonight.

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Old 03-27-2002, 12:38 AM
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Even without the offshore housing have drilled lewgs the way the guys are describing unless it isn't a High Performance motor. Right above where the lower unit attaches 5 holes are drilled on each side. The relief helps on the bottom end cause the motor can expell exhaust much easier but that is about the only gain. If you leg isn't drilled there is an option of mouting a snout like you can find at Bob's Machine Shop which you can plug for quite times and unplug for making some noise.
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Old 03-27-2002, 10:17 AM
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Shane--i have a land and sea exhaust that goes on the mid section--also comes with plugs to shut it up--works well
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Old 03-27-2002, 10:20 AM
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Is that the one that opens above a certain speed? Neat idea but defeats the purpose of relieved exhaust by working only above 55 mph.
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Old 03-27-2002, 10:58 AM
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No--it is open all the time and it does releive the exhaust pressure around the prop (if your using a chopper) helping the holeshot a bit--the holes are aiming down towards the water and are at the water line so at idle it isn't too loud--it looks like the merc offshore mid-section
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