Exhaust bellows delete

Y

Yankeyspeed

Petty Officer 3rd Class
Joined
Jun 10, 2012
Messages
92
I picked up an '84 Rinker with a 3.0 and when the PO did the bellows a couple of years ago he left out the exhaust bellows. He claimed that he read somewhere that it picked up some HP/TQ. I have been reading on 3.0 engines for some time, and not come across that. Has anyone else?
 
Don S

Don S

Honorary Moderator Emeritus
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Aug 31, 2004
Messages
62,321
Re: Exhaust bellows delete

Not going to happen on a 3.0L. Sounds more like a story a PO would tell to explain why he didn't install it.

Mercruiser went to a tube on the BIG BLOCK engines in order to help stop back pressure, but they did not eliminate it.
The bellows (or tube) is used to direct exhaust through the prop, without the bellows, you do not have the flow through the prop the props were designed to run with.

The tube is used a lot now by DIYers to lazy to do the job correctly with a bellows. You gain no HP on the smaller engines. It will be a little louder and make you think something is better. :facepalm:
 
kmarine

kmarine

Chief Petty Officer
Joined
Nov 5, 2010
Messages
581
Re: Exhaust bellows delete

I dont believe you will see a difference in power, but many people leave them off. The bellows have slits in them and usuially break after about 5 years. As for the exhaust, sending it through the prop creates a vacume effet and the research has not found any significant power loss or gain except in high power racing drives, which cant hardly be compared. You may only see a small reduction in noise if you replace the bellows. It is simply a preference wheather you replace them or leave it alone.
 
B

Bamaman1

Lieutenant Commander
Joined
May 15, 2011
Messages
1,895
Re: Exhaust bellows delete

You should put it back on. Remember to use the Mercruiser bellows cement, which is black and greasy stuff.

It's not that hard of a job to perform. You can have the outdrive completely off the boat in about 5 minutes.
 
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Exhaust bellows delete

Yankeyspeed said:
I picked up an '84 Rinker with a 3.0 and when the PO did the bellows a couple of years ago he left out the exhaust bellows. He claimed that he read somewhere that it picked up some HP/TQ. I have been reading on 3.0 engines for some time, and not come across that. Has anyone else?
Click to expand...

Mercruiser went to a tube on the BIG BLOCK engines in order to help stop back pressure, but they did not eliminate it.
The bellows (or tube) is used to direct exhaust through the prop, without the bellows, you do not have the flow through the prop the props were designed to run with.
Click to expand...

Yeah. When I got my 21' FourWinns from my brother and it still had the 460 King Kobra installed, I was decided to replace both the main bellows and the exhaust.

The exhaust was missing! When I asked my brother about it he said what bellows? It was switched from thru-hull exhaust to a Capt's-Call about 15 years before I got it.

The installer had not installed an exhaust bellows when he installed the y-pipe and diverter valves.

It ran that way for all those years (with no ex bellows) and no one noticed.

It was a bit noisier (compared to using a bellows) , but that was about it.

Even switching from "thru-drive" to thru-hull (with the switch), although it was REALLY LOUD, made virtually no performance difference.

It just irritated bejeebies out of everyone else!
 
Y

Yankeyspeed

Petty Officer 3rd Class
Joined
Jun 10, 2012
Messages
92
Re: Exhaust bellows delete

In order to appease my wife, I will most likely put it back on. I just got done doing the bellows on my other Rinker.
 
cr2k

cr2k

Captain
Joined
Mar 19, 2009
Messages
3,730
Re: Exhaust bellows delete

No bellows cement is used on the exhaust. Drive bellows yes.
 
L

LDO6490

Cadet
Joined
Mar 3, 2012
Messages
15
Re: Exhaust bellows delete

When replacing all of the bellows, I went lazy and replaced exhaust bellows with a tube. Afterwards, the wife complained that it was too loud, so went back and replaced the tube with a bellows. Purchased and used a GLM bellows install tool, which made it easy. Boat and wife are much quieter now. I didn't notice any performance difference between the tube or bellows.
 
M

MarkSee

Lieutenant Junior Grade
Joined
Sep 10, 2010
Messages
1,172
Re: Exhaust bellows delete

Yankeyspeed said:
I was thinking that the glue got hot with exhaust. Then cause problems.
Click to expand...

Seems to me the adhesive is more of the "keep the bellows in place until the clamp gets tightened" aid.
Maybe the experts with more experience can comment on if the adhesive is really suppose to hold a bellows in place for any length of time once the boat has been launched again and a clamp comes loose.

I am one of the guys who actually like the slightly louder sound of the tube and when I heard my Sea Ray with 454 that came stock with a tube, pulled the exhaust bellows off my 4.3 and put on the tube. Maybe it just kind of reminds me of the late 70's when I ran my '71 Gremlin down the drag strip with open exhaust.....

Don't know if my wife even noticed any difference in the sound, not even sure I mentioned what I changed out probably only said something like "doesn't that sound nice"..... But to be fair, I don't make comments on the things she buys for the house which is her domain. She buys what she wants and I just like it.

Mark
 
L

LDO6490

Cadet
Joined
Mar 3, 2012
Messages
15
Re: Exhaust bellows delete

Yankeespeed... Use a tube or bellows. The drive was designed for exhaust to be routed through the prop. No bellows or tube defeats that. Tube is an easy install with only one clamp on the transom side. There is a hole on the left side of the gimbal housing so you can fit a long skinny screwdriver to access the clamp screw.

Mark, I hear ya. More noise was good to me as it sounded like an old Camaro I had in high school. Unfortunately, wife's policy is what hers is hers and whats mine is part hers. Marriage is awesome!
 
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