Starboard exhaust manifold warmer and inspecting

[MarcelSydney]

Maxum 1800 SR with 1999 mercruiser 4.3L V6 with Alpha One, gen 2
Engine #OL 323311
Drive#OL140489

Salt water boat on trailer. Flush and wash after every use with salt away.
Manifolds and risers were replaced in 2019 about 100 hra ago, new impellor 6mths ago, new t-stat. In the past few months when running on the muffs when flushing, I've noticed the starboard manifold is hotter than port side and less water coming from that side out the back, and its quite hot to put hand under the water coming out. When the boat is in the water it's even temp.
1. Is this indicative of blockage developing?
2. Can you back/reverse flush the system to see if it clears anything? How do you do it if so?
3. How often should I inspect manifolds risers and what exactly am I looking for?
4. Should I be changing gaskets every so often (read that on another forum to do it every year)?

Thanks

 

[Scott Danforth]

tilt the boat the other way so the port manifold sits higher and the port side will be hotter.

since you are not level the higher manifold gets less water

you pull the elbows to inspect the joint between the manifold and elbow. you are looking at the gasket thickness area and how much of the metal has rusted away. always use OEM gaskets (not the sierra green leakers)

 

[Lou C]

I would check it as it sits in the water, as Scott noted gravity plays a role in manifold & elbow temps. Every 5 seasons or as soon as you see any leaks from the joint between the elbow and the manifold you should inspect. You will drain the manifolds/elbows, dis-assemble and check the water passages for clogging and heavy flaking rust and after cleaning up the sealing surfaces you'd want to check for pitting. You want a good clean surface that is free of pits and not eroded by rust. At 5 seasons I'd probably figure on replacing the elbows and fill the manifolds with acetone (off the boat, careful, flammable) to see if there are any leaks from the water passage to the exhaust gas passage. Sometimes you can replace the elbow and re-use the manifold, because the corrosion is usually worse on the elbow. If in doubt though replace both, a rust through failure can trash your engine.
Do you have the wet joint system (left pic) or the newer dry joint system? Dry joint is not prone to leaks at that joint but can still rust through! (right pic)

 

[MarcelSydney]

Thanks Scott and Lou. I'll try on the water to see if a difference before I pull off.
Assuming that the system can't be reverse flushed then to unblock if there is a blockage?

Dry joint vs wet joint: not sure what I have. Is it possible to tell from looking at them while in the boat?

I read that dry joint seems to be superior on other posts. When replacing manifolds/risess, are they interchangeable (I.e can I switch to dry joint setup if I have wet currently without major modifications needed)?

 

[Lou C]

I believe it can be done, but the dry joint is quite a bit more expensive. Ping achris he will know for sure...

The Ultimate Guide To Exhaust Manifolds, Risers & Exhaust Elbows On A Boat

Exhaust manifolds, risers and exhaust elbows can cause big trouble on a boat engine. Here is the most important information you need to know!

boatbuy.com.au

What is Dry Joint Exhaust? | PerfProTech.com

Large selection of quality mercruiser parts, marine engines, marine parts, boats parts and accessories, such as Mercuiser engines, exhaust, motors, and other boating supplies and accessories. Find affordable parts for leading brands including Volvo marine parts, Mercury marine parts, Quicksilver...

www.perfprotech.com

 

[QBhoy]

very common thing to be honest..water will flow to the path of least resistance...causes this effect. Try pumping one tyre up, haha.

 

[Lou C]

Can’t really reverse flush one of these systems but you can hook up a garden hose to the manifold water inlet and flush it that way, might get rid of minor clogs.

 

[MarcelSydney]

I believe it can be done, but the dry joint is quite a bit more expensive. Ping achris he will know for sure...

The Ultimate Guide To Exhaust Manifolds, Risers & Exhaust Elbows On A Boat

Exhaust manifolds, risers and exhaust elbows can cause big trouble on a boat engine. Here is the most important information you need to know!

boatbuy.com.au

What is Dry Joint Exhaust? | PerfProTech.com

Large selection of quality mercruiser parts, marine engines, marine parts, boats parts and accessories, such as Mercuiser engines, exhaust, motors, and other boating supplies and accessories. Find affordable parts for leading brands including Volvo marine parts, Mercury marine parts, Quicksilver...

www.perfprotech.com

Thanks. Haven't had much time lately but this is a pic of my manifolds. From what I can see they look like "wet joint". Is that right?
So I guess they should be taken off for an inspection as its been about 2.5 yrs since being installed?

 

[Lou C]

yes you have the wet joint

 

[QBhoy]

I wouldn’t bother, to be honest. Put her in the water and see what happens. It’s normal for one side to be warmer than the other when on a trailer and sometimes in the water too. Water flows it’s easiest route.
Unless you mean it’s like scolding hot and has seen an overheat before now…possibly causing a flapper to melt and block the exit of water.
But yeah…I’d see how she is when in water and all is normal.

 

[Lou C]

When the boat is on the trailer the lower side will be cooler and the higher side will be hotter if the trailer doesn't sit level. Even if the boat sits perfectly level in the water (not so common) due to the design of the thermostat housing the flow is not exactly even on both sides. In the water mine runs approx 10-15* hotter on the starboard side. Get an IR temp gun to leave on the boat and take readings then and see what you have.

 

[MarcelSydney]

Ok, thanks all. Will do.
So, when they talk about inspecting the manifolds/elbows/risers every couple of years and replacing every 5-7 (I'm exclusively using in salt), is that inspection something that I should be doing, given its been a couple of years. Or is it inspecting every 5 years, and replacing the elbows every 5yrs, but checking the manifolds are ok using the acetone test (and replacing less frequently)?

 

[tpenfield]

The only thing I'd add to the discussion is to check the thermostat housing for blockage and the hose leading to the hotter exhaust manifold.

Any restriction there would cause an imbalance of flow, similar to a restriction in the manifold/elbow itself.

Maybe get an IR heat gun to check the difference in temperature between the 2 sides of the engine.

 

[Lou C]

Ok, thanks all. Will do.
So, when they talk about inspecting the manifolds/elbows/risers every couple of years and replacing every 5-7 (I'm exclusively using in salt), is that inspection something that I should be doing, given its been a couple of years. Or is it inspecting every 5 years, and replacing the elbows every 5yrs, but checking the manifolds are ok using the acetone test (and replacing less frequently)?

I would inspect every 5 years but more or less count on at least replacing the elbows then; removing the manifolds to do the acetone test and deck the sealing surfaces (especially with wet joint systems). If you have wet joint manifolds if you see any sign of rust trails coming from between the manifold & elbow then inspect right away. When I had the one piece OMC manifolds on my V6 I just changed them every 5-6 seasons. Never had a leak back into the engine on that replacement schedule.

 

[achris]

Mercruiser exhaust systems.

Exhaust systems 101 Mercury’s introduction of ‘dry-joint’ manifolds (and elbows) seems to have caused more confusion than it needs to. So let’s try to unpack that confusion, and understand what is essentially a very simple system. Before we go much further here’s a picture of the various parts...

forums.iboats.com

 

[MarcelSydney]

Mercruiser exhaust systems.

Exhaust systems 101 Mercury’s introduction of ‘dry-joint’ manifolds (and elbows) seems to have caused more confusion than it needs to. So let’s try to unpack that confusion, and understand what is essentially a very simple system. Before we go much further here’s a picture of the various parts...

forums.iboats.com

Thanks. I actually read this post a little while ago. The pictures aren't displaying when I look at them (like another member mentioned). I use Chrome and checked my settings, and the pictures aren't blocked. Same when i try using Edge.
Are they still displaying when you look at them?
I'd really like to be able to see them as the post is great content. Any ideas?

 

[achris]

A while ago Photobucket pulled the proverbial rug on us (everyone using their free hosting service). Without warning they imposed a 'fee to use', and as most of us were using the free service, because it was free, we all did what they DIDN'T expect. We didn't pay any fees, and found other servers to host pictures. I thought I'd go one better and used my ISP allocated webspace, and all the pictures in my 'explainer' documents are (were) links to the pictures on my ISP. That went really well, until somehow my ISP started getting blocked by various browsers or other ISPs. That's why you can't see the pictures. I have migrated most of my documents over to iboats picture server, but it look like this is one I missed...

I'll do it now...

Apologies for the inconvenience.

Chris........

 

[achris]

.... The pictures aren't displaying ...

Try now.

 

[Lou C]

Thanks. Haven't had much time lately but this is a pic of my manifolds. From what I can see they look like "wet joint". Is that right?
So I guess they should be taken off for an inspection as its been about 2.5 yrs since being installed? View attachment 357561

If installed 2.5 years ago and we see no sign of leaking from that joint I’d say you’re still good. Another check I do is I replace the plugs in the spring after burning off the fogging oil. Look at the electrodes on the old plugs for any sign of corrosion. Even if you wouldn’t normally change plugs still inspect them for any corrosion and if you do see any then yes it’s time to drain the water and check the exhaust.

 

[MarcelSydney]

A while ago Photobucket pulled the proverbial rug on us (everyone using their free hosting service). Without warning they imposed a 'fee to use', and as most of us were using the free service, because it was free, we all did what they DIDN'T expect. We didn't pay any fees, and found other servers to host pictures. I thought I'd go one better and used my ISP allocated webspace, and all the pictures in my 'explainer' documents are (were) links to the pictures on my ISP. That went really well, until somehow my ISP started getting blocked by various browsers or other ISPs. That's why you can't see the pictures. I have migrated most of my documents over to iboats picture server, but it look like this is one I missed...

I'll do it now...

Apologies for the inconvenience.

Chris........

Thanks Chris. That's great. Works now.
BTW, as Lou mentioned earlier, is it possible to replace manifolds and elbows from wet joint to dry joint?