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Installing Exhaust Bellows on 5.7GXi's
https://www.smwebhead.com/phpBB3/viewtopic.php?f=6&t=10150		 Page 1 of 2
Author:  billcruise [ Mon Aug 20, 2012 8:18 pm ]
Post subject:  Installing Exhaust Bellows on 5.7GXi's
I have the 320 horse 5.7 GXi's and have always liked these with the 328 except for the noise level at cruise. I understand that among other things, VP removed the exhaust bellows to attain the horsepower level. I would be more than willing to give up for example 20 HP per engine to get a quiet cruise. Would installing these do any damage or increase the load on the engines? They currently have ~250 hrs.
Author:  alanurt [ Mon Aug 20, 2012 10:03 pm ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
I have that motor and have run without and now with. I don't recall noticing a difference in noise or performance.
Author:  ric [ Tue Aug 21, 2012 7:23 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
Probably nothing noticeable.
Author:  Borchik [ Tue Aug 21, 2012 8:01 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
They did not remove the bellows, if its not there it fell off or someone else removed it. big block engines have a tube that does not attach to the drive but mates to it when the drive is down all the way. they use these on big engines because the regular bellows acts like a potatoe in the tailpipe and restricts the exhaust flow.
Author:  Cap'n Morgan [ Tue Aug 21, 2012 8:18 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
Isn't the 5.7L Gxi just a beefed up small block 350?
Author:  ric [ Tue Aug 21, 2012 8:32 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
Cap'n Morgan wrote:
Isn't the 5.7L Gxi just a beefed up small block 350?


It's a full power un-molested vortec 350 from chevy. Not beefed up at all. It's actually stock. Any other 5.7 from Mercruiser/VP in the last 15 years is actually beefed down so it's not 320 +/- hp by removing GM's stock vortec crate engine cam and installing a milder one. Also by restricting the air intakes (crappy manifolds and 2bbl carbs).

If you want the full power "marine" cam... AKA the mercruiser hot cam...
http://paceperformance.com/i-6255412-14 ... t-350.html
Author:  jsimon [ Tue Aug 21, 2012 8:39 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
Now I get it. Our last boat a '03 268, had the 5.7 volvo duo prop 280 hp, and I never noticed it as being loud. A friend of ours has a '00 268 with the 5.7 merc 320 hp, and we went on a trip with them, he said he couldn't hear his marine radio over the noise of the motor.

They must be doing something different with the exhaust.
Author:  ric [ Tue Aug 21, 2012 8:46 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
You guys gave me a great idea how to squeeze a few ponies out of my 4.3 :)
Author:  Graham R [ Tue Aug 21, 2012 11:54 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
I got hacked off with the exhaust noise from my 5.7GXi with the "high flow" exhaust straight stub pipe and MHP transom shield, the noise made even worse due to reverberation of the swim platform.

I fitted the complete exhaust bellows version for last season. It's noticeably quieter and, sorry Ric, it doesn't appear to have reduced the power, there's no difference in WOT RPM or general performance compared to previous years. Maybe the stub exhaust brings something for the big blocks: it's not going back on my boat though ! The only problem is that I can now hear other noises that I worry about !

As it was put on as an experiment, I used an aftermarket one as it was about half the VP price. The internal circlip that came with it that retains the bellows to the tilt housing wouldn't fit inside the bellows, so I didn't use one. The bellows stayed in place.
Author:  Cap'n Morgan [ Tue Aug 21, 2012 12:05 pm ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
ric wrote:
You guys gave me a great idea how to squeeze a few ponies out of my 4.3 :)


Not sure you can do that with an SX drive
Author:  Graham R [ Tue Aug 21, 2012 2:54 pm ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
Cap'n Morgan wrote:
ric wrote:
You guys gave me a great idea how to squeeze a few ponies out of my 4.3 :)


Not sure you can do that with an SX drive


Not so much the SX drive affecting HP (or DPS for that matter, the upper units are the same), but there are 2 distinct transom shields. The standard has a single anode, the MHP ( = minimum hydrostatic pressure, I believe) has 2 anodes which do not impede exhaust flow, more mounting studs plus different setup of the lower and upper steering pivots. I don't kmow if there are any other differences that result in increased exhaust flow; the single exhaust stub ( plus of course the standard bellows) can be fitted to both..
Author:  billcruise [ Thu Aug 23, 2012 6:19 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
Graham R wrote:
I got hacked off with the exhaust noise from my 5.7GXi with the "high flow" exhaust straight stub pipe and MHP transom shield, the noise made even worse due to reverberation of the swim platform.

I fitted the complete exhaust bellows version for last season. It's noticeably quieter and, sorry Ric, it doesn't appear to have reduced the power, there's no difference in WOT RPM or general performance compared to previous years. Maybe the stub exhaust brings something for the big blocks: it's not going back on my boat though ! The only problem is that I can now hear other noises that I worry about !

As it was put on as an experiment, I used an aftermarket one as it was about half the VP price. The internal circlip that came with it that retains the bellows to the tilt housing wouldn't fit inside the bellows, so I didn't use one. The bellows stayed in place.


Graham, can you share the part numbers for items you installed? Or what you would recommend since the circlip is not compatible?
Author:  Graham R [ Thu Aug 23, 2012 7:14 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
The VP circlip is compatible with the VP bellows, the previous boat I had was fitted with one and it always fitted in place easily ( it fits inside the bellows at the tilt housing end). I've no idea why the aftermarket one wouldn't fit, maybe the rubber was thicker; it proved unnecessary to use one with that item as it turned out. The OEM one is bronze, the aftermarket one stainless steel.

The part numbers for the MHP tilt housing is the same as for the standard of the same year. so there shouldn't be any compatability issues

Bellows: 3850426

Retainer (circlip): 3852665

There might be "kit " available containing both the bellows and retainer; If I was using the VP bellows, I would also use the retainer.
ps: The bellows has drain holes in it.

Graham

http://www.marinepartsexpress.com/VP_Schematics/MARINE%20DRIVE%20&%20TRANSMISSION/SX-M_DP-SM/TRANSMISSIONS/Gimbal%20Ring%20and%20Pivot%20Housing0.pdf
Author:  billcruise [ Thu Aug 23, 2012 9:12 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
Graham R wrote:
The VP circlip is compatible with the VP bellows, the previous boat I had was fitted with one and it always fitted in place easily ( it fits inside the bellows at the tilt housing end). I've no idea why the aftermarket one wouldn't fit, maybe the rubber was thicker; it proved unnecessary to use one with that item as it turned out. The OEM one is bronze, the aftermarket one stainless steel.

The part numbers for the MHP tilt housing is the same as for the standard of the same year. so there shouldn't be any compatability issues

Bellows: 3850426

Retainer (circlip): 3852665

There might be "kit " available containing both the bellows and retainer; If I was using the VP bellows, I would also use the retainer.
ps: The bellows has drain holes in it.

Graham

http://www.marinepartsexpress.com/VP_Schematics/MARINE%20DRIVE%20&%20TRANSMISSION/SX-M_DP-SM/TRANSMISSIONS/Gimbal%20Ring%20and%20Pivot%20Housing0.pdf


I assume item 23 clamp is required as well? Can this be installed without removing the drives? I may attempt doing this in the water.
Author:  Graham R [ Thu Aug 23, 2012 10:01 am ]
Post subject:  Re: Installing Exhaust Bellows on 5.7GXi's
The clamp is the same as on the exhaust hose you already have. A new one might come with the "kit" ( it did with the aftermarket one)

You should certainly be able to remove the old hose in the water, with the drive tilted up fully. The outdrive end of the bellows has to be pushed through into the pivot housing. There's a lip on it's end on it that sits inside the housing, you might be able to do it by pushing a little of that lip through at a time and then rotating it, repeating the process until all the lip is through. It's probably easier doing it that way than attaching the forward clamp and continuity wire first. A lot depends on how warm the water is/ how soft the rubber is. You won't be able to insert the retainer/ circlip at the outdrive end without removing the drive though.

Graham
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