Concerns with exhaust

[sinlessearth]

Alpha 1 gen 2, 3.0 tks. Recently I had an exhaust shutter fall apart due to heat which caused a few issues in the stern drive. I have since fixed the stern drive and replaced the shutter. The exhaust bellow looks a little rough too. The boat is 12 years old and this is the first time I had this happen. Boat has never been in salt water however it did sit for a few years is storage. My question is. Should I be concerned with the exhaust manifold heating up or would old age cause the shutter issue? Also, when I store it for each month should I leave the water in or drain every time? No worries on winter since this is in Florida. After I fixed the shutter I ran it up and noticed rust come out. Any thoughts will help. Thank you.

 

[Scott Danforth]

the shutter issue is from lack of cooling water. lack of cooling water takes the exhaust from a 200 degree mix of water and exhaust to 1100 degrees of pure exhaust and burns all the rubber pieces up.

did you replace the raw water impeller?

while you had it apart, did you replace the other bits of rubber, or at a minimum inspect them?

 

[airshot]

12 years is way past the bellows life expectancy....especially if the boat sits in the water!

 

[Chris1956]

Didn't MerCruiser change to a exhaust tube, versus a bellows?

 

[Scott Danforth]

Didn't MerCruiser change to a exhaust tube, versus a bellows?

Mercruiser offered the tube on big block units and people use it on the smaller motors. they did not change to it. its just an alternate offering.

 

[sinlessearth]

the shutter issue is from lack of cooling water. lack of cooling water takes the exhaust from a 200 degree mix of water and exhaust to 1100 degrees of pure exhaust and burns all the rubber pieces up.

did you replace the raw water impeller?

while you had it apart, did you replace the other bits of rubber, or at a minimum inspect them?

I replaced the carrier assembly seal, impeller, water tube and seals. I only discovered the shutter since it was stuck in the lower when I was replacing the carrier assembly seal. Since it was stuck it deformed the tube.

When I looked at the rubber on the exhaust it was fine but exhaust bellow a some deformation inside.

 

[sinlessearth]

12 years is way past the bellows life expectancy....especially if the boat sits in the water!

Yeah probably. The boat has never sat in water, except when it's in use, so no longer than 12hrs. I inspected the bellows and the universal joint bellow is fine and looks good. No deformation, cracking or dry rot. I'm sure they need replaced.

My main concern is doing the work to replace the parts and shutter just to have it happen again. Due to something I missed or didn't think about.

 

[flashback]

I wouldn't worry about the exhaust bellows. I would put a tube in.

 

[Scott06]

Yeah probably. The boat has never sat in water, except when it's in use, so no longer than 12hrs. I inspected the bellows and the universal joint bellow is fine and looks good. No deformation, cracking or dry rot. I'm sure they need replaced.

My main concern is doing the work to replace the parts and shutter just to have it happen again. Due to something I missed or didn't think about.

Exhaust bellows can be torn and nothing will happen. They are full of water when boat is at rest because exhaust gets routed to the prop hub.
if your driveshaft bellows and shift bellows are good leave it alone. I ran several season with a torn exhaust bellows before I did a complete transom reseal job.

if it over heated that is why the shutter failed and you can wreck more components due to high temp. Watch the temp gauge and use OEM merc impellers as they last forever in fresh water. i have. Done my neighbors 10 yr old factory impeller looked essentially new. Did mine after 6 yrs same thing. Worth the money for oem rubber parts. My bellows except exhaust lasted 18 years and were not leaking yet…

 

[sinlessearth]

Exhaust bellows can be torn and nothing will happen. They are full of water when boat is at rest because exhaust gets routed to the prop hub.
if your driveshaft bellows and shift bellows are good leave it alone. I ran several season with a torn exhaust bellows before I did a complete transom reseal job.

if it over heated that is why the shutter failed and you can wreck more components due to high temp. Watch the temp gauge and use OEM merc impellers as they last forever in fresh water. i have. Done my neighbors 10 yr old factory impeller looked essentially new. Did mine after 6 yrs same thing. Worth the money for oem rubber parts. My bellows except exhaust lasted 18 years and were not leaking yet…

Thanks for the info. I used OEM impeller and the old one looked good to me which is why I'm concerned about the exhaust. But it was the 12 year old original. There was no obvious signs of overheating. The gauge was always mid range and never got too hot.

Should I drain the block and manifold before storing it a few months at a time or leave the water in it? Just wondering which way would cause less rust. I would think leaving the water in would be better but not sure.

 

[sinlessearth]

I wouldn't worry about the exhaust bellows. I would put a tube in.

I'll have to look this up. I didn't know this was an option .

 

[Scott06]

Thanks for the info. I used OEM impeller and the old one looked good to me which is why I'm concerned about the exhaust. But it was the 12 year old original. There was no obvious signs of overheating. The gauge was always mid range and never got too hot.

Should I drain the block and manifold before storing it a few months at a time or leave the water in it? Just wondering which way would cause less rust. I would think leaving the water in would be better but not sure.

Drain it but shortly two more people will come by and give you three different answers.
are you in fresh or salt? For best results therotically drain and back fill without anitfreeze with corrosion inhibitor ( aka not the $3/ gal chit at Walmart)

 

[Scott06]

I'll have to look this up. I didn't know this was an option .

The bellows are a PITA to change so a lot of guys use the exhaust tube that only connects on the transom end.
with the bellows expansion tool I did not find it terrible to but the exhaust bellows on. Would I want to do that job every week.. no but not a deal breaker