06-14-2009, 10:55 AM #1
Drilling Out Exhaust on 200 Blackmax
I have a 21 Checkmate Enchanter with a 1989 Mercury 200 hp Blackmax. The engine is in great condition. I am in the process of upgrading the carbs and heads, and I have always wanted to drill out the exhaust in the midsection of the outboard since I bought it. My only concern is that I have never done a modification like this before so I don't know the correct drilling location, or what size the holes should be. Any information on drilling location, and steps for the procedure would be greatly appreciated.
06-14-2009, 11:05 AM #2
WELCOME TO SCREAM AND FLY !!!!!!
Many varied opinions on the subject. Several years back Mercury had 260's mounted on a 20" midsection called a "Bass Mid" they had a cavitation plate at the base of the mid and had 5 1/2" holes drilled at that point on each side and was very popular. The way to drill these point the power head would need to be removed and the inner liner with a long drill bit to drill through the inner part of the ledge from the inside. From the outside it is not visable ( keeps lake patrol off ya butt ) but has a sweet sound. Other methods use hole saws from the out side BUT this mod is very visable and I have seen cracks and failures doing the mods any other way that the stock Bass Mid way..
BTW you sure have a good looking rig !
JayJay @ JSRE
06-14-2009, 01:14 PM #3
Judge85 Welcome to SNF....
great place to BS, meet people and spend a GREAT DEAL OF MONEY!Boatless..... but plotting
06-14-2009, 01:20 PM #4
09-18-2013, 07:15 PM #5
Sorry to bring on an old dead theard!! I'm also new to SNF. That link does not work...wish I could find the step by step
09-18-2013, 07:49 PM #6
I had a friend actually almost burn up his boat and the fuel dock with a hole sawed center section. He had just fueled and spilled some in the water via the fuel tank vent. When he cranked the engine it popped through the exhaust and set the water on fire all around the back of the boat. Just burned for a few seconds but talk about scaring the fuel dock attendants!
I did one with the 1/2" holes as described above. Works well, sounds good, and is below the surface off plane so you can talk while idling through the no wake zones.18 Talon/2.4 carb
26 Deck Boat/175 Merc
09-18-2013, 07:51 PM #7
09-18-2013, 08:13 PM #8
bobs machine shop has a kit..
Last edited by quicklt1; 09-18-2013 at 08:16 PM.
09-18-2013, 09:26 PM #9
I just drill the lower above the cav. plate into the exhaust chamber between the rear driveshaft cavity boss and divider plate! 2-holes on each side about 1" and then dremel them oval them to 1x1-1/4 leaving the hole walls tapered to the rear!doesn't sound any different than my bass style exhaust relief mid,real quiet until they pop out of the water! simple to plug if someone gives you grief about the "race" motor!
09-18-2013, 09:27 PM #10
kit?????? ive drilled out gobs of them what a kit for drilling 10 holes you just need to have can gasket is all dont remove the power head its a slow job that way remove lower then can off of clamp its fast no power head gaskets
09-19-2013, 04:15 AM #11
Yes.. bobs machine shop makes a kit look it up..It has a housing that you can plug and looks cool also..
09-19-2013, 04:41 AM #12
09-19-2013, 06:07 AM #13
96' STV Euro
Smarta$$ of the Sunshine Syndicate,
How to upload pics (click here)
09-20-2013, 06:06 PM #14
Today I had the day off....I took the boat out of the shleter...dropped the lower end unit...had the mid section almost free....but the bumpers/connection to the pivoting shaft....How in hell do you take the mid section off them? I had the covers and clamps off...The bolt and bushing...man I must sound dumb? I'm I the only one?
you guys been so great so far I was almost there.
Also...Taking the can off. wouldn't it eat up the impeller pump maybe causing it to deteriorate faster?
09-21-2013, 06:30 PM #15
Are the nuts for the upper mounts spinning, or did you get them off?