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View Full Version : Motor/Mechanical MORON needs help!!!



oldLenny
11-15-2003, 04:54 PM
OK, I am moving my side exhaust on the GT21 from hull-sides to transom again. I have STOCK Mercruiser exhaust (cast) I am NOT changing them, but I need to know how to locate the holes at the transom. I do NOT want Quick and Quiet or anything, only OPEN exhaust. (No rules here, or will there ever be on the ocean)

How do I locate the centers on the transom?

Do I use 4" exhaust?

Do I make them lower than the risers or straight back?

Any thoughts from anyone, other than spending money on stuff I don't want?
...now I am getting challenged..I don't do motors "stuff"...help please..I will help when I can with things I know about...

Thanks, ...Lenny

BUIZILLA
11-15-2003, 05:07 PM
Lenny, do you have the stock logs, or the stock center risers??

J

oldLenny
11-15-2003, 05:30 PM
The big black thingy's (new-ish) have the exhaust coming up from the "center-ish" of the big black thingy...

Rootsy
11-15-2003, 09:12 PM
Lenny,

i believe mercruiser has a print of where to locate the exhaust tips on the transom relative to the crankshaft centerline of the motor... check a few of the exhaust suppliers like imco, emi, Stainless marine, corsa/gil.. i don't think i have it on my puter or i'd send ti to you..

the tips exit a bit lower than the outlet of the risers... you can see this if you look at them from teh side.. they kinda angle down a bit...

you are gonna want to run 4 inch tips. the outlets on the risers are for 4 inch hose. guess you could always put em on. put a piece of 4 inch exhaust hose on that extends to the transom.. trace a circle around em then true the circles up so that they are in the same location.

Scott Pearson
11-16-2003, 05:53 AM
Lenny,
Call me....I can go over it with you and take measurements off of my 18. Its the same set up! I also have the paper work Rootsy is talking about.

(732)886-5498

(NJ)Scott

Greg K
11-16-2003, 06:15 AM
When I did the exhaust holes on my 16 with a small block and stock merc risers, center to center of exhaust outlets were 27". 4-1/8 hole saw was used to cut them.

oldLenny
11-17-2003, 11:30 AM
I have stock risers (center). 27" c/c sounds fine. I can do this. BUT, are they lower, is there an angle supposed to be brought into the equation?...hole size? 4 1/8" works for all 4"?

ScoTt P, my fax number is 250.391.9663 if anyone has any neat stuff to help me...Thanx in advance. Pearson, I just might call you this eve...Lenny

olredalert
11-17-2003, 11:42 AM
Lenny,

------I think that you always want a slight downward angle going toward the transom as that allows water to dribble out after the engine is shut off.......Bill S

MOP
11-17-2003, 04:35 PM
Lenny just an opion when the boat is at rest they all seem to sit A$$ down I would think that should cover the draining of the pipes.

tailwind
11-17-2003, 07:26 PM
Send us a drawing, and will be happy to send you a cnc manifold match up! Youre choice: 3/16" , 1/4" thickness< you name it! mild steel _ best or stainless?

BigGrizzly
11-17-2003, 09:00 PM
If it is a bravo there is a standard measurement I can't find mine, but randy Leider at CMI has it, that is why they have exhaust "for bravo drives" any give them a call.

oldLenny
11-17-2003, 11:26 PM
Volvo 270, stock. Stock 350 Chev with Stock center risers Grizz...