1989 292 sr1
01-24-2005 | 07:42 PM
#13
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From: Northeast,Fla
Re: 1989 292 sr1
Originally Posted by Formula Outlaw
I just finished a 379 (per Cuda Count) project on my boat which included ditching the Silent Thunder Box and going with Stainless Marine tips with the internal flappers.
I like the looks of the "classic" offshore boat and have always HATED those rectangular exhaust tips.
Between dropping the box and swapping to an Eddie Marine Thunder aluminum exhaust system, I lost over 400 lbs of dead weight right over the props. Docked, the boat now sits over an inch higher out of the water at the stern, so I just dropped an inch on my "X" demension. At least "it" thinks so. The first time I fired it off on the hose it was all worth it.-
I like the looks of the "classic" offshore boat and have always HATED those rectangular exhaust tips.
Between dropping the box and swapping to an Eddie Marine Thunder aluminum exhaust system, I lost over 400 lbs of dead weight right over the props. Docked, the boat now sits over an inch higher out of the water at the stern, so I just dropped an inch on my "X" demension. At least "it" thinks so. The first time I fired it off on the hose it was all worth it.-
01-24-2005 | 08:29 PM
#14
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From: In the Mountains
Re: 1989 292 sr1
Originally Posted by MadMat
Yeh, I was watching your progress with interest. Unfortunately I boat exclusively in salt water, I'm pretty nervous about aluminium exhausts, plus on a pair of 330hp 7.4's I doubt a performance exhaust would make much difference unless I start changing the heads too, which the budget won't stretch too this year. I do know where there's a pair of bulldogs for sale though 
I boat in the Gulf of Mexico, no problems with aluminum exhaust systems as long as you remember to ALWAYS flush your motors good after running in salt. Anyone who "trailer's" their boat around salt water use aluminum trailers exclusively.
In any motor, any time you can make it "breathe" better you are going to increase it's performance. Obviously some motors much more than others, but you will see some increase. Particularly over the stock Mercruiser manifolds, as they are just one big cavern inside and the exhaust gases end up just bouncing around all over the place until they ultimately find their way out. Plus you save 85 lbs. per motor.
01-24-2005 | 08:31 PM
#15
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From: In the Mountains
Re: 1989 292 sr1
Originally Posted by MadMat
Do you mind me asking which tips you went for? Are they the 4" straight flange straight end with the internal 'super flap'? They look sweet.
Stainless Marine. Love'em. Got them from "Trick Marine" here on OSO. And they are exactly as you described.
01-28-2005 | 04:37 PM
#17
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From: Eastern Lake Ontario
Re: 1989 292 sr1
Originally Posted by Formula Outlaw
On my 89' 311 it is exactly 34 and 1/2 inches measured from the front of the drives. The propshaft, center to center is 34 and 1/4 inches so I have a slight "toe-in".
01-28-2005 | 08:53 PM
#19
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From: In the Mountains
Re: 1989 292 sr1
Originally Posted by ThirdBird
Nope. You're toed-out dude!!
I was misinformed. I was told that "in or out" was depending on the propshafts center to center, not the leading edge. Thanks for the correction.
What would be the best thing to do???? Increase the propshaft "center to center" distance over the leading edge distance. I think I'm starting to get confused.
I've got "outward" turning props so the way I understand it, the "prop torque" or whatever it's called, will cause the centerline of the propshafts to "diminish" slightly, is that correct?
Or do I have this azz backwards? Now I'm really confused.....not hard to do.
What is the ideal set up? Or is it one of those things you just have to keep screwing around with????
Last edited by Formula Outlaw; 01-28-2005 at 08:56 PM.
01-28-2005 | 09:31 PM
#20
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From: 1000 Islands
Re: 1989 292 sr1
for the terminology, think toe in/toe out as if you're looking at the front tires of your car.
Front of gearcase measures farther apart than propshafts= toe out and vise versa. 1/4" or more toe "in" most often is the setup to have. It's most often neutralized (gearcase over it's length made parallel to the bottom
) by the water pushing to the outside (moreso against the inside leading edge of the gearcase) off the V shape of the hull after it leaves the bottom. It's not hard to picture in your mind's eye if you think about the forces at work, and the way a V-bottom displaces water, and how it wants to find it's way back.
Front of gearcase measures farther apart than propshafts= toe out and vise versa. 1/4" or more toe "in" most often is the setup to have. It's most often neutralized (gearcase over it's length made parallel to the bottom
) by the water pushing to the outside (moreso against the inside leading edge of the gearcase) off the V shape of the hull after it leaves the bottom. It's not hard to picture in your mind's eye if you think about the forces at work, and the way a V-bottom displaces water, and how it wants to find it's way back.
